Lernstörungen im multilingualen Kontext: Diagnose und Hilfestellungen.

Book published by Melusina Press (2021)

Um Kinder mit einer Lernstörung durch möglichst angepasste Hilfsmaßnahmen unterstützen zu können, ist eine umfassende Diagnostik maßgeblich. Die Diagnostik von Lernstörungen stellt vor allem in multilingualen Kontexten - wie in Luxemburg - eine Herausforderung dar. Auch werden derzeit vorwiegend im Ausland entwickelte diagnostische Tests durchgeführt, welche die luxemburgischen Besonderheiten, wie etwa das Erlernen der schriftsprachlichen und mathematischen Kompetenzen in einer Zweit- oder Drittsprache, nicht berücksichtigen. Ausgehend vom aktuellen Forschungs- und Wissensstand wird ein vertieftes Verständnis im Hinblick auf Lese- und Rechtschreibstörungen und Rechenstörungen dargelegt. Darauf aufbauend werden diagnostische Vorgehensweisen sowie pädagogische Hilfsmaßnahmen mithilfe von Erfahrungswerten praktizierender Fachkräfte aus dem luxemburgischen Förderbereich vorgestellt.

Harmonic amplitude summation for frequency-tagging analysis

in Journal of Cognitive Neuroscience (2021)

In the approach of frequency tagging, stimuli that are presented periodically generate periodic responses of the brain. Following a transformation into the frequency domain, the brain’s response is often evident at the frequency of stimulation, F, and its higher harmonics (2F, 3F, etc.). This approach is increasingly used in neuroscience, as it affords objective measures to characterize brain function. However, whether these specific harmonic frequency responses should be combined for analysis, and if so, how, remains an outstanding issue. In most studies, higher harmonic responses have not been described or were described only individually; in other studies, harmonics have been combined with various approaches, e.g., averaging and root mean squared summation. A rationale for these approaches in the context of frequency-based analysis principles, and understanding of how they relate to the brain’s response amplitudes in the time domain, has been missing. Here, with these elements addressed, the summation of (baseline-corrected) harmonic amplitude is recommended.

Varying stimulus duration reveals consistent neural activity and behavior for human face individuation

in Neuroscience (2021), 472

Establishing consistent relationships between neural activity and behavior is a challenge in human cognitive neuroscience research. We addressed this issue using variable time constraints in an oddball frequency-sweep design for visual discrimination of complex images (face exemplars). Sixteen participants viewed sequences of ascending presentation durations, from 25 to 333 ms (40–3 Hz stimulation rate) while their electroencephalogram (EEG) was recorded. Throughout each sequence, the same unfamiliar face picture was repeated with variable size and luminance changes while different unfamiliar facial identities appeared every 1 s (1 Hz). A neural face individuation response, tagged at 1 Hz and its unique harmonics, emerged over the occipito-temporal cortex at 50 ms stimulus duration (25–100 ms across individuals), with an optimal response reached at 170 ms stimulus duration. In a subsequent experiment, identity changes appeared non-periodically within fixed-frequency sequences while the same participants performed an explicit face individuation task. The behavioral face individuation response also emerged at 50 ms presentation time, and behavioral accuracy correlated with individual participants’ neural response amplitude in a weighted middle stimulus duration range (50–125 ms). Moreover, the latency of the neural response peaking between 180 and 200 ms correlated strongly with individuals’ behavioral accuracy in this middle duration range, as measured independently. These observations point to the minimal (50 ms) and optimal (170 ms) stimulus durations for human face individuation and provide novel evidence that inter-individual differences in the magnitude and latency of early, high-level neural responses are predictive of behavioral differences in performance at this function.

Switching language while solving math problems: Relation between language and math achievement on a bilingual math test

Scientific Conference (2020, June)

Impact of learning to read in a mixed approach on neural tuning to words in beginning readers

in Frontiers in Psychology (2020), 10

The impact of learning to read in a mixed approach using both the global and phonics teaching methods on the emergence of left hemisphere neural specialization for word recognition is yet unknown in children. Taking advantage of a natural school context with such a mixed approach, we tested 42 first graders behaviorally and with Fast Periodic Visual Stimulation using electroencephalographic recordings (FPVS-EEG) to measure selective neural responses to letter strings. Letter strings were inserted periodically (1/5) in pseudofonts in 40 s sequences displayed at 6 Hz and were either words globally taught at school, that could therefore be processed by visual whole-word form recognition (global method), or control words/pseudowords eliciting graphemephoneme (GP) mappings (phonics method). Results show that selective responses (F/5, 1.2 Hz) were left lateralized for control stimuli that triggered GP mappings but bilateral for globally taught words. It implies that neural mechanisms recruited during visual word processing are influenced by the nature of the mapping between written and spoken word forms. GP mappings induce left hemisphere discrimination responses, and visual recognition of whole-word forms induce bilateral responses, probably because the right hemisphere is relatively more involved in holistic visual object recognition. Splitting the group as a function of the mastery of GP mappings into “good” and “poor” readers strongly suggests that good readers actually processed all stimuli (including global words) predominantly with their left hemisphere, while poor readers showed bilateral responses for global words. These results show that in a mixed approach of teaching to read, global method instruction may induce neural processes that differ from those specialized for reading in the left hemisphere. Furthermore, given their difficulties in automatizing GP mappings, poor readers are especially prone to rely on this alternative visual strategy. A preprint of this paper has been released on Biorxiv (van de Walle de Ghelcke et al., 2018).

The Relationship Between the Benton Face Recognition Test and Electrophysiological Unfamiliar Face Individuation Response as Revealed by Fast Periodic Stimulation.

in Perception (2020), 49(2), 210-221

A recent approach to implicitly study face recognition skills has been the fast periodic visual stimulation (FPVS) coupled with electroencephalography (EEG). Its relationship with explicit behavioral measures of face individuation remains largely undocumented. We evaluated the relationship of the FPVS–EEG measure of individuation and performance at a computer version of the Benton Face Recognition Test. High-density EEG was recorded in 32 participants presented with an unfamiliar face at a rate of 6Hz (F) for 60 s. Every five faces, new identities were inserted. The resulting 1.2 Hz (F/5) EEG response and its harmonics objectively indexed rapid individuation of unfamiliar faces. The robust individuation response, observed over occipitotemporal sites, was significantly correlated with speed, but not accuracy rate of the computer version of the Benton Face Recognition Test. This effect was driven by a few individuals who were particularly slow at the behavioral test and also showed the lowest face individuation response. These results highlight the importance of considering the time taken to recognize a face, as a complementary to accuracy rate variable, providing valuable information about one’s recognition skills. Overall, these observations strengthen the diagnostic value of FPVS–EEG as an objective and rapid flag for specific difficulties at individual face recognition in the human population.

Units-first or tens-first: Does language matter when processing visually presented two-digit numbers?

in Quarterly journal of experimental psychology (2006) (2020), 73(5), 726-738

The linguistic structure of number words can influence performance in basic numerical tasks such as mental calculation, magnitude comparison, and transcoding. Especially the presence of ten-unit inversion in number words seems to affect number processing. Thus, at the beginning of formal math education, young children speaking inverted languages tend to make relatively more errors in transcoding. However, it remains unknown whether and how inversion affects transcoding in older children and adults. Here we addressed this question by assessing two-digit number transcoding in adults and fourth graders speaking French and German, that is, using non-inverted and inverted number words, respectively. We developed a novel transcoding paradigm during which participants listened to two-digit numbers and identified the heard number among four Arabic numbers. Critically, the order of appearance of units and tens in Arabic numbers was manipulated mimicking the "units-first" and "tens-first" order of German and French. In a third "simultaneous" condition, tens and units appeared at the same time in an ecological manner. Although language did not affect overall transcoding speed in adults, we observed that German-speaking fourth graders were globally slower than their French-speaking peers, including in the "simultaneous" condition. Moreover, French-speaking children were faster in transcoding when the order of digit appearance was congruent with their number-word system (i.e., "tens-first" condition) while German-speaking children appeared to be similarly fast in the "units-first" and "tens-first" conditions. These findings indicate that inverted languages still impose a cognitive cost on number transcoding in fourth graders, which seems to disappear by adulthood. They underline the importance of language in numerical cognition and suggest that language should be taken into account during mathematics education.

Developmental changes in neural letter-selectivity: A 1-year follow-up of beginning readers.

in Developmental science (2020)

The developmental course of neural tuning to visual letter strings is unclear. Here we tested 39 children longitudinally, at the beginning of grade 1 (6.45 ± 0.33 years old) and 1 year after, with fast periodic visual stimulation in electroencephalography to assess the evolution of selective neural responses to letter strings and their relationship with emerging reading abilities. At both grades, frequency-tagged letter strings were discriminated from pseudofont strings (i.e. letter-selectivity) over the left occipito-temporal cortex, with effects observed at the individual level in 62% of children. However, visual words were not discriminated from pseudowords (lexical access) at either grade. Following 1 year of schooling, letter-selective responses showed a specific increase in amplitude, a more complex pattern of harmonics, and were located more anteriorly over the left occipito-temporal cortex. Remarkably, at both grades, neural responses were highly significant at the individual level and correlated with individual reading scores. The amplitude increase in letter-selective responses between grades was not found for discrimination responses of familiar keyboard symbols from pseudosymbols, and was not related to a general increase in visual stimulation responses. These findings demonstrate a rapid onset of left hemispheric letter selectivity, with 1 year of reading instruction resulting in increased emerging reading abilities and a clear quantitative and qualitative evolution within left hemispheric neural circuits for reading.

The effect of grade retention on reading skills of immigrant children in multilingual elementary school. A longitudinal study.

Presentation (2019, November 06)

In a longitudinal study the effect of grade retention on reading skills of immigrant children in multilingual elementary school was investigated. The study was conducted between 2013 and 2017 and thirty-four per cent of the sample was lost due to grade retention. These children had been followed from kindergarten to grade 3 of elementary school. To observe differences among promoted and retained students, we assessed them using various language and socioeconomic measures. We also compared a subgroup of promoted students, scoring lower in grade 2 than the mean of retained students in reading comprehension. The current study revealed four main findings. Firstly, there were no significant differences between promoted and retained students in their first language vocabulary (Portuguese). Secondly, there was a significant difference in second and third language vocabularies (Luxembourgish and German) and in German reading tasks (the language of instruction) from kindergarten to grade 2, with promoted students scoring higher than retained students. Thirdly, and most importantly, retained students did not catch up with promoted students in the language of instruction (German) measures even after grade retention, but they did in language of socialisation (Luxembourgish). Fourthly, and in contrast to retained students, the low-achieving promoted students improved significantly in German reading comprehension by grade 3.The last two findings underline that grade retention does not lead to improvement in children’s reading comprehension. As vocabulary is one of the main predictors of reading comprehension, programs that improve poor readers’ vocabulary knowledge may be more efficient than grade retention. The present findings corroborate previous studies reporting that grade retention is not beneficial and that low-achieving students promoted to the next grade show better academic outcomes later than retained students.

Weaker neural responses to lexicality and word frequency in dyslexic adults: an EEG study with Fast Periodic Visual Stimulation.

Scientific Conference (2019, September)

Dyslexia, a persistent reading disorder, is characterized by different brain activation patterns when reading. Here, we used a Fast Periodic Visual Stimulation paradigm during EEG recordings to assess the sensitivity of dyslexics to fine-grained psycholinguistic variations of letter strings: lexicality, lexical frequency, and orthographic regularity. Dyslexic and non-dyslexic students watched 60-seconds streams of stimuli presented at 10Hz, in which deviant items are inserted periodically (1/8, at 1.25Hz). Results show discrimination responses at 1.25Hz over left posterior occipito-temporal regions, reduced in dyslexics. Group differences were significant for discrimination of word lexicality and frequency, but not for word regularity. These results show that FPVS response amplitude distinguishes normal from pathological population. Since explicit reading is prohibited by the fast rate, results suggest differences of automatic and implicit word processing in dyslexics. The lack of group difference for regular/irregular words is interpreted post-hoc as reflecting the life-long drill of dyslexics to irregular words.

Are dates processed like words rather than like numbers? A study of transposition priming effects

Poster (2019, May)

Neuropsychological case-studies suggested that dates and encyclopedic numbers may be processed differently than unknown numbers. However, this issue was not yet investigated in reading in healthy participants, so that it is unclear if dates are read like words and processed as lexical items, or like numbers where each position strictly defines the digit value in a base-10 system. Here, we compared processing of known dates to unknown numbers in a group of 26 experts (students and teachers in History). Participants performed an explicit recognition task on dates (e.g., 1789, 1945, …) and on acronyms (e.g., FNRS, HDMI, …), half known and half unknown. They were preceded by an identical prime (e.g., 1945-1945), a transposed-character prime (e.g., 1495-1945) or a substituted-character prime (e.g., 1635-1945). Results show that for dates, there is a significant transposition gain (-57ms), while for unknown numbers as well as for acronyms (known and unknown), the transposed-character prime induced a cost (from +17 to +257ms) rather than a gain. The facilitation due to transposed characters found here on dates is similar to what is observed in studies of lexical decision on words. Therefore, it suggests that dates may be processed with similar types of orthographical mechanisms than words.

A minority pulls the sample mean: on the individual prevalence of robust group-level cognitive phenomena - the instance of the SNARC effect

Presentation (2019, January)

Spatial Skills First: The Importance of Mental Rotation for Arithmetic Skill Acquisition

in Journal of Numerical Cognition (2019)

The relation between visuospatial abilities and verbal number skills in preschool: Adding spatial language to the equation

Poster (2018, September)

MaGrid: A Language-Neutral Early Mathematical Training and Learning Application

in International Journal of Emerging Technologies in Learning (2018), 13(08), 4-18

Given that the use of educational technologies is increasingly popular in kindergarten and among young students, these technologies have been shown to be able to solve the difficulties (existing in school) that are either not possible to be solved in traditional schooling or cost a lot of time and resources. In this paper, we present a pedagogical training and learning application called MaGrid (Math on Grid), which has been developed to foster early mathematical skills in pre-schoolers. MaGrid is a tablet-based application, which provides a wide range of training tasks targeting fundamental mathematical concepts for the preschool level. The language-neutral property of MaGrid is an innovative aspect that makes MaGrid different from existing mathematical training applications. This property may reduce the barrier of language from mathematical education for second language learners encountered in multilingual school settings. MaGrid allows individual learning in an interactive way and provides real-time feedback. Moreover, MaGrid is capable of recording students’ activities while working on the training tasks, which can help teachers and parents keep track of a student’s progress in different tasks and observe potential training-related improvements over time. Finally, we describe a series of experiments carried out using the MaGrid application during special training and assessment sessions in several preschools in Luxembourg.

Taking Language out of the Equation: The Assessment of Basic Math Competence Without Language

in Frontiers in Psychology (2018)

While numerical skills are fundamental in modern societies, some estimated 5–7% of children suffer from mathematical learning difficulties (MLD) that need to be assessed early to ensure successful remediation. Universally employable diagnostic tools are yet lacking, as current test batteries for basic mathematics assessment are based on verbal instructions. However, prior research has shown that performance in mathematics assessment is often dependent on the testee’s proficiency in the language of instruction which might lead to unfair bias in test scores. Furthermore, language-dependent assessment tools produce results that are not easily comparable across countries. Here we present results of a study that aims to develop tasks allowing to test for basic math competence without relying on verbal instructions or task content. We implemented video and animation-based task instructions on touchscreen devices that require no verbal explanation. We administered these experimental tasks to two samples of children attending the first grade of primary school. One group completed the tasks with verbal instructions while another group received video instructions showing a person successfully completing the task.We assessed task comprehension and usability aspects both directly and indirectly. Our results suggest that the non-verbal instructions were generally well understood as the absence of explicit verbal instructions did not influence task performance. Thus we found that it is possible to assess basic math competence without verbal instructions. It also appeared that in some cases a single word in a verbal instruction can lead to the failure of a task that is successfully completed with non-verbal instruction. However, special care must be taken during task design because on rare occasions non-verbal video instructions fail to convey task instructions as clearly as spoken language and thus the latter do not provide a panacea to non-verbal assessment. Nevertheless, our findings provide an encouraging proof of concept for the further development of non-verbal assessment tools for basic math competence.

Overcoming language barriers in early mathematics instruction with “MaGrid” - a language-neutral training tool for multilingual school settings

Poster (2018, April 08)

Mathematical knowledge at the onset of formal schooling paves the way for children’s achievement in formal mathematics (e.g. Duncan et al., 2007; Watts et al., 2014). Hence, it is crucial to equip children with sound basic mathematical competencies by deploying effective teaching interventions during preschool years. However, multilingual school settings, such as Luxembourg (65% of the pupils are second language learners) pose a special challenge for instruction. Non-native pre-schoolers perform lower on early mathematics tests than their age-matched peers (Bonifacci et al., 2016; Kleemans et al., 2011). This gap is most likely due to missing out on learning opportunities, as a result of lower proficiency in the language of instruction. To provide equal access to early mathematics education for all children, we developed a language-neutral early mathematics training tool, the “MaGrid”-app. This innovative training tool has been evaluated, so far, in two studies in multilingual Luxembourg. In a first study, children from five classrooms (N = 68) used the tool to train visuo-spatial abilities, an important predictor of mathematical abilities (see e.g. Mix et al., 2016), over ten weeks (2x20min/week). At post-test, significant gains in the visuo-spatial domain were observed, compared to children from “teaching-as-usual” classrooms (N = 57). In a second study, we elaborated a comprehensive language-neutral early mathematics intervention, with “MaGrid” at its core. Findings from both training studies will be presented in detail and the importance of domain-specific versus domain-general precursors, as well as practical implications, will be discussed.

Visuo-spatial abilities are key for young children’s verbal number skills

in Journal of Experimental Child Psychology (2018), 166C

Children’s development of verbal number skills (i.e, counting abilities and knowledge of the number names) presents a milestone in mathematical development. Different factors such as visuo-spatial and verbal abilities have been discussed to contribute to the development of these foundational skills. To understand the cognitive nature of verbal number skills in young children, the present study assessed the relation of preschoolers’ verbal and visuo-spatial abilities to their verbal number skills. In total, 141 children aged between five and six years participated in the present study. Verbal number skills were regressed on vocabulary, phonological awareness and visuo-spatial abilities, as well as verbal and visuo-spatial working memory in a structural equation model. Only visuo-spatial abilities emerged as a significant predictor of verbal number skills in the estimated model. Our results suggest that visuo-spatial abilities contribute to a larger extent to children’s verbal number skills than verbal abilities. From a theoretical point of view, these results suggest a visuo-spatial, rather than a verbal, grounding of verbal number skills. These results are potentially informative for the conception of early mathematics assessments and interventions.

Developmental changes in the effect of active left and right head rotation on random number generation

in Frontiers in Psychology (2018)

A rapid, objective and implicit measure of visual quantity discrimination

in Neuropsychologia (2018), 111

There is evidence that accurate and rapid judgments of visual quantities form an essential component of human mathematical ability. However, explicit behavioural discrimination measures of visual quantities are readily contaminated both by variations in low-level physical parameters and higher order cognitive factors, while implicit measures often lack objectivity and sensitivity at the individual participant level. Here, with electrophysiological frequency tagging, we show discrimination differences between briefly presented visual quantities as low as a ratio of 1.4 (i.e., 14 vs. 10 elements). From this threshold, the neural discrimination response increases with parametrically increasing differences in ratio between visual quantities. Inter-individual variability in magnitude of the EEG response at this population threshold ratio predicts behavioural performance at an independent number comparison task. Overall, these findings indicate that visual quantities are perceptually discriminated automatically and rapidly (i.e., at a glance) within the occipital cortex. Given its high sensitivity, this paradigm could provide an implicit diagnostic neural marker of this process suitable for a wide range of fundamental and clinical applications.

LEARN Newsletter - Editioun 2018

Book published by LEARN (2018)

The relevance of verbal and visuo-spatial abilities for verbal number skills – what matters in 5 to 6 year olds?

Poster (2017, September)

The acquisition of verbal number skills, as defined by the meaningful use of number words, marks a milestone in numerical development. In the present study, we were particularly interested in the question, whether verbal number skills are primarily verbal in nature, or if they call upon visuo-spatial processes, reflecting a spatial grounding of verbal number skills. 141 five- to six-year old children were tested on a range of verbal (i.e. vocabulary, phonological awareness and verbal working memory) and visuo-spatial abilities (i.e. spatial perception, visuo-motor integration and visuo-spatial working memory). We were particularly interested in the predictive role of these abilities for children’s verbal number skills (as measured by different counting and number naming tasks). In a latent regression model, basic visuo-spatial abilities, measured by spatial perception and visuo-motor integration, emerge as the most important predictor of verbal number skills. This gives raise to the assumption, that verbal number skills are, despite their verbal nature, spatially grounded in young children.

Project NUMTEST: Assessing basic number competence without language

Poster (2017, May 31)

While numerical skills are fundamental in modern societies, some estimated 5-7% of children suffer from a mathematical learning disorder, called developmental dyscalculia (DD). Nevertheless, universally valid diagnostic instruments are still lacking, as all current DD test batteries are based on language instructions. Consequently, their measurements are tightly linked to the specific language context of test administration and thus their results cannot easily be compared across countries. Here we are showing results of the first pilot study of a research project that aims to develop a test for basic math abilities that does not rely on language instruction and minimizes language use. To this aim, video and animation based instructions were implemented on touchscreen devices. A first version of the tasks has been tested with two samples of first grade children in Luxembourg’s fundamental schools, of which half completed the same tasks with traditional verbal instructions. Our results indicate that performance in the experimental group was similar or better than the control group using verbal instructions. Relationships between linguistic background and the sample’s performance on one hand and qualitative usability aspects of nonverbal task instruction and tablet-pc use with young children will be discussed.

Training early visuo-spatial abilities: A controlled classroom-based intervention study.

in Applied Developmental Science (2017)

Visuo-spatial training can be considered as a promising approach to provide young children with a sound foundation for later mathematical learning. We developed and implemented a tablet-based visuo-spatial intervention in kindergarten classrooms aiming to foster the development of children’s visuo-spatial and numerical abilities. A sample of N = 125 children participated in the present study, 68 children were part of the intervention group and participated in 20 training sessions of 20 minutes over a 10-week period, 57 children formed a business as usual control group. Results show that, at this young age, visuo-spatial and early math skills are already strongly interlinked. However, the training effects were domain-specific as they only improved visuo-spatial skills, but did not transfer to early math performance in the present setting.

Project NUMTEST; Assessing basic number competence without language

Poster (2017, February 20)

While numerical skills are fundamental in modern societies, some estimated 5-7% of children suffer from a mathematical learning disorder, called developmental dyscalculia (DD). Nevertheless, universally valid diagnostic instruments are still lacking, as all current DD test batteries are based on language instructions. Consequently their measurements are tightly linked to the specific language context of test administration and thus their results cannot easily be compared across countries. The present study is the first pilot study of a research project that aims to develop a test for basic math abilities that does not rely on language instruction and minimizes language use. To this aim, video and animation based instructions were implemented on touchscreen devices. A first version of the application has been tested with a sample of first grade children in Luxembourg’s fundamental schools, of which half used the same application but with traditional German instructions. First results indicate that performance in the experimental group was similar to the control group using verbal instructions. Relationships between linguistic background and the sample’s performance on one hand and qualitative usability aspects of nonverbal task instruction and tablet use with young children will be discussed.

How and Why Do Number-Space Associations Co-Vary in Implicit and Explicit Magnitude Processing Tasks?

in Journal of Numerical Cognition (2017)

LEARN Newsletter - Editioun 2017: Méisproochegkeet

Book published by LEARN (2017)

Mental arithmetic in the bilingual brain: Language matters.

in Neuropsychologia (2017), 101

How do bilinguals solve arithmetic problems in each of their languages? We investigated this question by exploring the neural substrates of mental arithmetic in bilinguals. Critically, our population was composed of a homogeneous group of adults who were fluent in both of their instruction languages (i.e., German as first instruction language and French as second instruction language). Twenty bilinguals were scanned with fMRI (3T) while performing mental arithmetic. Both simple and complex problems were presented to disentangle memory retrieval occuring in very simple problems from arithmetic computation occuring in more complex problems. In simple additions, the left temporal regions were more activated in German than in French, whereas no brain regions showed additional activity in the reverse constrast. Complex additions revealed the reverse pattern, since the activations of regions for French surpassed the same computations in German and the extra regions were located predominantly in occipital regions. Our results thus highlight that highly proficient bilinguals rely on differential activation patterns to solve simple and complex additions in each of their languages, suggesting different solving procedures. The present study confirms the critical role of language in arithmetic problem solving and provides novel insights into how highly proficient bilinguals solve arithmetic problems.

How Math Anxiety relates to Number-Space Associations.

in Frontiers in Psychology (2016), 7(1401),

Given the considerable prevalence of math anxiety, it is important to identify the factors contributing to it in order to improve mathematical learning. Research on math anxiety typically focusses on the effects of more complex arithmetic skills. Recent evidence, however, suggests that deficits in basic numerical processing and spatial skills also constitute potential risk factors of math anxiety. Given these observations, we determined whether math anxiety also depends on the quality of spatial-numerical associations. Behavioral evidence for a tight link between numerical and spatial representations is given by the SNARC (spatial-numerical association of response codes) effect, characterized by faster left-/right-sided responses for small/large digits respectively in binary classification tasks. We compared the strength of the SNARC effect between high and low math anxious individuals using the classical parity judgment task in addition to evaluating their spatial skills, arithmetic performance, working memory and inhibitory control. Greater math anxiety was significantly associated with stronger spatio-numerical interactions. This finding adds to the recent evidence supporting a link between math anxiety and basic numerical abilities and strengthens the idea that certain characteristics of low-level number processing such as stronger number-space associations constitute a potential risk factor of math anxiety.

THE IMPACT OF LANGUAGE BACKGROUND ON BASIC MATH COMPETENCE

Poster (2016, April 02)

German number word system inverts units and tens compared to the Arabic notation. This is not the case in French, which is more transparent regarding the Arabic number code. Evidence indicates that the linguistic structure of number words can facilitate or impede numerical development (Zuber, Pixner, & Moeller, 2009). Moreover, in transcoding tasks more mistakes are made in non-transparent compared to transparent languages (Imbo, Vanden Bulcke, De Brauwer, & Fias, 2014). We used a new paradigm of transcoding task in which 28 French-speaking (FR) and 19 German-speaking (GE) 4th grade children had to listen two digits numbers. The new thing was that we manipulate the order of appearance of the units and the tens of the number in three conditions: Units-First (UF), Tens-First (TF) and Simultaneous (S). Then, the subjects had to choose the heard number among four numbers presented on the computer screen. Results sows that GE are globally slower than FR (F(1,45) = 3.95, p = .053). The largest difference was observed for the TF: (t(45) = -3.729, p = .001). Moreover, when the order of the number appearance was congruent with the number word system, the transcoding was faster in both languages. For GE the S condition was slower than TF condition (F(2,36) = 6.918, p = .008) and than UF condition (F(2,36) = 6.918, p = .003.). For FR, the TF was faster than S (F(2,54) = 69.419, p < .001) and UF (F(2,54) = 69.419, p < .001). All these data indicate that language structure qualitatively impacts on basic numerical tasks.

Cardinal and ordinal processing in spatial neglect

Poster (2016, January)

Patients with spatial neglect do not only have difficulties in orienting attention in physical space but also in representational space, especially with respect to the mental representation of numbers. Indeed, in a study by Zorzi et al. (2012) neglect patients were particularly slow when asked to compare the number 4 to the standard number 5, suggesting difficulties to process numbers on the left side of an internal standard. This difficulty was observed in a magnitude judgement, but not in a parity task, implying a dissociation between explicit and implicit processing of numerical magnitude. The present study aimed at replicating these findings and extending them to non-numerical sequences in order to complement the data obtained on bisection tasks (Zamarian, et al., 2007). Sixteen right-sided brain damaged patients with neglect (N+ =6; 4 females; all right handers; mean age: 55 +/- 8,7) and without neglect (N- =10; 2 females; all right hander; mean age: 48 +/- 6.2) participated in the study. They were administered the following tasks: a magnitude and a parity judgement task; an ordinal judgement task on numbers and on letters and a consonant/vowel classification task. For each task and each patient, a linear regression was computed in which the difference between the response times for the left effector (index finger) and the right effector (middle finger) was predicted by number magnitude. A negative slope will indicate the presence of a SNARC-like effect. We compared the negative slopes of the two patient groups using a Chi-square. Considering the proportion of SNARC-like effects, it appeared that, on one hand, N+ patients showed fewer SNARC-like effects than N- patients during magnitude judgements on numbers. Thus confirming the findings by Zorzi et al. (2012). On the other hand, N+ patients behaved similarly to N- patients for the parity judgements on numbers and for the order judgements both on numbers and letters. This last result suggest a dissociation between the spatial representation of magnitude and of order in N+ patients. These results point towards a specific impairment in explicit access to number magnitude in spatial hemineglect.

Solving arithmetic problems in first and second language: Does the language context matter?

in Learning and instruction (2016)

Learning mathematics in a second language is a challenge for many learners. The purpose of the study was to provide new insights into the role of the language context in mathematic learning and more particularly arithmetic problem solving. We investigated this question in a GermaneFrench bilingual educational setting in Luxembourg. Participants with increasing bilingual proficiency levels were invited to solve additions in both their first and second instruction languages: German and French. Arithmetic problems were presented in two different conditions: preceded by a semantic judgment or without additional language context. In the French session we observed that additions were systematically performed faster in the condition with an additional language context. In contrast no effect of the context was observed in the German session. In conclusion, providing a language context enhanced arithmetic performances in bilinguals' second instruction language. This finding entails implications for designing optimal mathematic learning environments in multilingual educational settings.

Math anxiety is predicted by the strength of number-space associations, over and beyond arithmetic ability and WM

Poster (2015, October)

Math skills are undeniably important in everyday life. Math anxiety can, however, threaten their optimal development. Given that a fifth of the population experiences high math anxiety, it is important to identify its origins in order to improve mathematical learning. Research on math anxiety typically focusses on the effects of math ability, WM, and spatial performance. Recent evidence, however, suggests that it also depends on basic numerical processes, with high math anxious individuals featuring less precise numerical representations, as indexed by stronger distance effects. Another marker for the nature of numerical representations is the SNARC effect, alluding to their spatial organization. Although number-space associations depend on WM, spatial performance and arithmetic ability - all related to math anxiety - their relationship with the latter has never been tested. We thus determined whether math anxiety is related to the strength of number-space associations. All participants (n=60, 28 female) completed the r-MARS, the parity judgment, an arithmetic, and visuospatial WM task. We replicated previous findings on the negative relationships between math anxiety and arithmetic ability (r=-0.3, p=0.02), and WM (r=-0.29, p=0.03). But most importantly, we found a significant negative correlation between the SNARC effect and math anxiety (slope=-11.42, r=-0.43, p<0.001), with high math anxious individuals featuring greater interference of the irrelevant magnitude-associated spatial code. Interestingly, number-space associations were the only significant predictor of math anxiety in a multiple regression analysis. Our findings thus provide further evidence for the association between numerical representations and math anxiety, over and beyond arithmetic ability and WM.

The link between number-space associations and visuospatial abilities depends on visualization profile

Poster (2015, September)

Background: Evidence for number-space associations comes from the spatial-numerical association of response-codes (SNARC) effect, consisting in faster RTs to small/large digits with the left/right hand respectively. However, the cognitive origin of the effect remains elusive. Previous studies suggested that it might depend on visuospatial processes, since individuals with better performances in 2D (but not 3D) mental rotation tasks displayed weaker number-space associations (Viarouge et al., 2014). Aims: Given the high inter-individual variability of number-space associations, we determined whether the SNARC effect always relies on visuospatial processes or whether its cognitive origin varies with visualization preferences. Method: We distinguished between object-visualizers (n=42, 23 female, age=22.93) and spatial-visualizers (n=42, 15 female, age=23.9) using the Object-Spatial Imagery Questionnaire (Blajenkova et al., 2006). All participants performed the parity judgment task, a 2D visuospatial test and a 3D mental rotation task. Results: In object-visualizers, weaker SNARC slopes were associated with better performances in the 2D (r=0.46, p=0.004), but not 3D (r=-0.04, p=0.79) task, thereby replicating previous observations. Conversely, in spatial-visualizers, the performances in both visuospatial tasks were unrelated to the SNARC effect (2D: r=0.02, p=0.89; 3D: r=0.2, p=0.22). Conclusions: These findings suggest that in object-visualizers, number-space associations and 2D performances underlie common visuospatial processes. Conversely, in spatial-visualizers, number-space associations seem to result from cognitive mechanisms other than those recruited during the aforementioned visuospatial tasks (e.g., verbal-spatial coding mechanisms). All in all, we were able to further unravel the mechanisms underlying number-space associations and could highlight visualization preferences as an additional explanation for the great inter-individual variability of the SNARC effect.

Functional connectivity and structural analyses in the bilingual brain: implications for arithmetic.

Poster (2015, June)

Do bilinguals use the same brain networks than monolinguals when they solve arithmetic problems? We investigated this question by using resting-state functional connectivity and cortical thickness measurements. Recent studies highlighted differences of functional connectivity (e.g. Grady et al., 2015) and of brain structure (e.g. Klein et al., 2014) between bilinguals and monolinguals. However, no study so far has linked these differences to arithmetic problem solving, a cognitive skill that may at least partially rely on language processing. Our study population was composed of carefully selected German-French bilinguals (N = 20) who acquired each language at the same age, leading to high proficiency levels in both languages. These bilinguals all attended university in their second language at the time of the experiment, namely French. Therefore we selected a control group of French-speaking monolinguals (N = 12). Structural and functional images of brain activity were collected using a 3T MRI scanner. Functional scans of resting-state were acquired during a 6-minute session, with eyes closed. A 3D T1-weighted data set encompassing the whole brain was acquired to provide detailed anatomy (1 mm3), which was used both for the co-registration of functional data and for morphometric analyses. Prior to the scanning session, all participants took a behavioral test measuring their arithmetic skill. For the resting-state part of the study, we generated spheres based on ROIs reported in the literature as magnitude manipulation- and language-related areas during arithmetic problem solving (Klein et al. 2013), and addition-related areas reported in a recent meta-analysis (Arsalidou & Tayor, 2011). We used these spheres as seed regions for the analyses. We correlated resting activations between these regions and compared these correlations in bilinguals versus monolinguals. Results showed significantly higher correlations between the three seed regions in monolinguals than in bilinguals (all ts > 2.306; ps < .05), suggesting that regions used to solve arithmetic problems form a different network in bilinguals than in monolinguals. To control for general differences between both populations, we also created two spheres in areas not specifically related to neither arithmetic nor language regions. There were no significant differences between groups in terms of correlations of these regions with resting-state activations. These results suggest that the differences observed in arithmetic problem solving regions could not account for by general differences between groups. In the second part of the study, we aimed at verifying whether the differences in functional connectivity we observed between bilinguals and monolinguals coincide with structural brain differences. We measured and compared cortical thickness in both groups. Then we compared the correlations between cortical thickness and arithmetic skill in both groups (considering differences with corrected p < .001). Cortical thickness of areas commonly associated to language or number processing correlated differently with arithmetic skill as a function of the group: Higher cortical thickness of left pars triangularis, bilateral superior parietal gyri and precuneus positively correlated with arithmetic skill in monolinguals but negatively correlated with arithmetic skill in bilinguals. These results highlight that there are different relations between brain structure and arithmetic skills in bilinguals and monolinguals. In conclusion the current study provides new evidence for differences between bilinguals’ and monolinguals’ brain networks engaged in arithmetic problem solving, even without any arithmetic task during the data acquisition. These findings based on functional connectivity and brain structure analyses also reveal the general involvement of language in arithmetic problem solving in bilingual as well as non-bilingual individuals.

Neural correlates of arithmetic problem solving in bilinguals: an fMRI study.

Poster (2015, May)

Inhibitory Control Influences the SNARC Effect in Tasks without Explicit Reference to Numerical Magnitude

Poster (2015, March)

Evidence for number-space associations comes from the spatial-numerical association of response-codes (SNARC) effect, consisting in faster reaction times to small/large digits with the left/right hand respectively. Although the SNARC effect has now been extensively replicated, it is characterized by high inter-individual variability (Wood et al., 2008). For instance, it has been shown to depend on inhibitory control as indexed by the color Stroop effect in the elderly, with individuals having weaker inhibitory control displaying stronger SNARC effects (Hoffmann et al., 2014). Apart from these well-documented inter-individual differences, number-space associations are also influenced by intra-individual factors. Georges et al. (2014) found that in a population of healthy young university students (n=85, 39 females, mean age=23.44 years), the SNARC effect was qualitatively different within single individuals depending on the number-processing task that they performed. While the strength of the SNARC effects were related in a parity and color judgment task (parity slope=-11.58; color slope=-6.79; r=0.36, p=0.001), as well as in the parity and a magnitude comparison task (magnitude slope=-6.98; r=0.36, p=0.001), no relation could be observed between number-space associations in the color and magnitude tasks (r=0.18, p=0.11). These findings indicate that two distinct factors seem to account for the variance related to number-space associations observed during the three tasks. In the present study, we built on these findings while investigating how inhibitory control influences variance in the SNARC effect observed during different numerical tasks. To this aim, we performed a principle component analysis followed by varimax rotation to combine the color and parity SNARC effects (i.e. number-space associations in tasks without explicit reference to numerical magnitude) and the parity and magnitude SNARC effects (i.e. number-space associations in tasks involving semantic number processing) into single factors (color-parity-SNARC and parity-magnitude-SNARC factors respectively). We then investigated how these two extracted SNARC factors were influenced by inter-individual characteristics such as inhibitory control. Inhibitory control was evaluated in a task that involved responding to the color (green or red) of a centrally presented arrow pointing either in the left or right direction by pressing on the left or right hand-side. To get a single inhibitory control measure for each individual, we calculated inverse efficiency scores on compatible and incompatible trials and computed performance differences between those two conditions. The scores of the extracted parity-color-SNARC factor significantly correlated with the inhibitory control measure (μ=109.98ms, SD=85.82ms; r=-0.26, p=0.02), while no relation was observed between inhibitory control and the parity-magnitude SNARC factor scores (r=-0.1, p=0.42). This suggests that individuals with better inhibitory control (i.e. smaller performance differences between compatible and incompatible trials) displayed weaker SNARC effects only in number-processing tasks that required the suppression of an irrelevant numerical (magnitude) code for successful task completion. Number-space associations are characterized by high inter- and intra-individual variability. We determined how the SNARC effect observed in tasks with and without explicit numerical magnitude processing related to inhibitory control. Individuals with better inhibitory control displayed weaker SNARC effects only in tasks requiring the suppression of an irrelevant numerical magnitude.

The relation between language and arithmetic in bilinguals: insights from different stages of language acquisition

in Frontiers in Psychology (2015), 6

Solving arithmetic problems is a cognitive task that heavily relies on language processing. One might thus wonder whether this language-reliance leads to qualitative differences (e.g., greater difficulties, error types, etc.) in arithmetic for bilingual individuals who frequently have to solve arithmetic problems in more than one language. The present study investigated how proficiency in two languages interacts with arithmetic problem solving throughout language acquisition in adolescents and young adults. Additionally, we examined whether the number word structure that is specific to a given language plays a role in number processing over and above bilingual proficiency. We addressed these issues in a German–French educational bilingual setting, where there is a progressive transition from German to French as teaching language. Importantly, German and French number naming structures differ clearly, as two-digit number names follow a unit-ten order in German, but a ten-unit order in French. We implemented a transversal developmental design in which bilingual pupils from grades 7, 8, 10, 11, and young adults were asked to solve simple and complex additions in both languages. The results confirmed that language proficiency is crucial especially for complex addition computation. Simple additions in contrast can be retrieved equally well in both languages after extended language practice. Additional analyses revealed that over and above language proficiency, language-specific number word structures (e.g., unit-ten vs. ten-unit) also induced significant modulations of bilinguals' arithmetic performances. Taken together, these findings support the view of a strong relation between language and arithmetic in bilinguals.

Inhibition of return and attentional facilitation: Numbers can be counted in, letters tell a different story.

in Acta psychologica (2015), 163

Prior research has provided strong evidence for spatial-numerical associations. Single digits can for instance act as attentional cues, orienting visuo-spatial attention to the left or right hemifield depending on the digit's magnitude, thus facilitating target detection in the cued hemifield (left/right hemifield after small/large digits, respectively). Studies using other types of behaviourally or biologically relevant central cues known to elicit automated symbolic attention orienting effects such as arrows or gaze have shown that the initial facilitation of cued target detection can turn into inhibition at longer stimulus onset asynchronies (SOAs). However, no studies so far investigated whether inhibition of return (IOR) is also observed using digits as uninformative central cues. To address this issue we designed an attentional cueing paradigm using SOAs ranging from 500ms to 1650ms. As expected, the results showed a facilitation effect at the relatively short 650ms SOA, replicating previous findings. At the long 1650ms SOA, however, participants were faster to detect targets in the uncued hemifield compared to the cued hemifield, showing an IOR effect. A control experiment with letters showed no such congruency effects at any SOA. These findings provide the first evidence that digits not only produce facilitation effects at shorter intervals, but also induce inhibitory effects at longer intervals, confirming that Arabic digits engage automated symbolic orienting of attention.

Horizontal tuning of face-specific processing from childhood to elderly adulthood.

Poster (2015)

Face recognition in adults recruits specialised mechanisms that are selectively driven by horizontal information. This range indeed conveys the most optimal and stable cues to identity. Whether the horizontal tuning of adult face recognition reflects horizontal bias already active at infancy and/or whether it also results from the extensive experience acquired with faces over the lifespan is elusive. Answering these questions is crucial to determine the information constraining the developmental specialisation of core visual functions such as face perception. Participants aged between 6 and 74 years matched unfamiliar faces that were filtered to retain information in narrow ranges centred on horizontal (H), vertical (V), or both orientation ranges (HV). H and V ranges respectively maximize and minimize the recruitment of face-specific mechanisms (Goffaux and Dakin, 2010). Stimuli were presented at upright and inverted planar orientations and the face inversion effect (FIE; i.e., better performance for upright than inverted faces) was taken as a marker of face-specific processing. In H and HV conditions, FIE size increased linearly from childhood to adulthood, manifesting the progressive specialization of face perception. FIE emerged earlier when processing HV than H faces (FIE onset: 6 and 12 years, respectively) indicating that until 12 years horizontal information is necessary but not sufficient to trigger face-specialised processing. Partial correlations further showed that FIE development in HV condition was not fully explained by FIE development in H condition. Besides a progressive maturation of horizontal processing, the specialization of the face processing system thus also depends on the improved integration of horizontal range with other orientations. In contrast, FIE size was small and stable when processing V information. These results show that the face processing system matures over the life span based on the refined encoding of horizontally-oriented (upright) face cues. Meeting abstract presented at VSS 2015.

Horizontal tuning for faces originates in high-level Fusiform Face Area.

in Neuropsychologia (2015), 81

Recent work indicates that the specialization of face visual perception relies on the privileged processing of horizontal angles of facial information. This suggests that stimulus properties assumed to be fully resolved in primary visual cortex (V1; e.g., orientation) in fact determine human vision until high-level stages of processing. To address this hypothesis, the present fMRI study explored the orientation sensitivity of V1 and high-level face-specialized ventral regions such as the Occipital Face Area (OFA) and Fusiform Face Area (FFA) to different angles of face information. Participants viewed face images filtered to retain information at horizontal, vertical or oblique angles. Filtered images were viewed upright, inverted and (phase-)scrambled. FFA responded most strongly to the horizontal range of upright face information; its activation pattern reliably separated horizontal from oblique ranges, but only when faces were upright. Moreover, activation patterns induced in the right FFA and the OFA by upright and inverted faces could only be separated based on horizontal information. This indicates that the specialized processing of upright face information in the OFA and FFA essentially relies on the encoding of horizontal facial cues. This pattern was not passively inherited from V1, which was found to respond less strongly to horizontal than other orientations likely due to adaptive whitening. Moreover, we found that orientation decoding accuracy in V1 was impaired for stimuli containing no meaningful shape. By showing that primary coding in V1 is influenced by high-order stimulus structure and that high-level processing is tuned to selective ranges of primary information, the present work suggests that primary and high-level levels of the visual system interact in order to modulate the processing of certain ranges of primary information depending on their relevance with respect to the stimulus and task at hand.

Shifts of spatial attention cued by irrelevant numbers: Electrophysiological evidence from a target discrimination task

in Journal of Cognitive Psychology (2014)

Fischer et al. demonstrated that a centrally presented number can shift attention to the left/right when its magnitude is small/large. Two electrophysiological studies described these attentional effects as eventrelated potentials (ERPs) at centro-parietal sites. Since both studies used target detection tasks, it remains currently unknown whether similar results would be obtained with a discrimination task. We used ERPs to test whether digit cues also induce attention shifts when participants perform a feature discrimination task on targets. ERPs were recorded whereas subjects discriminated the colour of lateral targets that were preceded by a central non-predictive digit. Analysis of cue-locked controlateral vs. ipsilateral ERP activity showed the emergence of early preparatory attention-directing components in parietal and frontal regions. Moreover, target-locked P1 components at occipito-parietal sites were significantly modulated by digit magnitude-target side congruency. These results demonstrate that irrelevant digit cues also bias sensory processing when embedded in a feature-discrimination task.

Waat as Dyscalculie?

Conference given outside the academic context (2014)

Arithmetic in the Bilingual Brain: an fMRI study

Scientific Conference (2014, May)

How do bilinguals solve arithmetic problems in their different languages? We investigated this question with functional magnetic resonance imaging (fMRI) by exploring the neural substrates of arithmetic processing in bilinguals in comparison to monolinguals. Bilingual participants were highly proficient both in German and French as they attended primary school in German and secondary school and higher education in French. This bilingual combination is particularly interesting because the order of two-digit number words is inversed in these languages: decade-unit in French but unit-decade in German. 21 German-French bilinguals and 12 French-speaking monolinguals were scanned while performing different types of arithmetic problems: additions of different complexity levels (from simple to complex additions) and multiplication facts. We presented different types of operations in order to disentangle arithmetic computation from pure memory retrieval that occurs in very simple additions or multiplications. Arithmetic problems were presented via headsets in a verification paradigm and bilinguals performed the tasks in both languages. Results showed that all arithmetic tasks elicited a broad fronto-parietal network in both groups and for both of bilinguals’ language sessions. However, we observed that complex additions involved more left frontal activity (i.e. inferior frontal gyrus, anterior cingulate gyrus) in bilinguals than in monolinguals. It is important to notice that these frontal activation differences occurred both for the arithmetic acquisition language (i.e. German) and the second language (i.e. French). These BOLD differences between bilingual and monolingual participants were observed despite the fact that both groups solved the arithmetic problems with equivalent accuracy rates. Moreover, localization of the regions activated by complex additions in bilinguals differed from the typical activation pattern reported for mental arithmetic in recent meta-analyses (Arsalidou & Taylor, 2011). Taken together, our results indicate that highly proficient bilinguals rely on differential activation patterns than monolinguals to solve complex additions. The differences in left frontal activations might reflect different degrees of language-related automaticity when computing complex arithmetic problems. Executive functions that are necessary to control language context and access for bilinguals’ respective languages might also play a role. Further insights about the role of language in arithmetic solving process in bilingual and non-bilingual individuals will be discussed.

Canonical finger numeral configurations are perceived holistically

Poster (2014, April 04)

Sooner or later human beings represent or see numerosities represented by hands. This handling of small numerosities by prototypical finger configurations has been the focus of many experiments investigating the possibility that semantic representations of numbers are motor-rooted. Canonical finger configurations (i.e. the culturally determined way to express numerosity with fingers) are for instance recognized faster (Di Luca et al., 2006), and give direct access to number semantics (Di Luca et Pesenti, 2008). It is also known that these effects are not due to a visual facilitation of canonical configurations (Di Luca et Pesenti, 2010), but to a different inner representation (Di Luca, Lefèvre and Pesenti, 2010). However, a precise characterization of their visual processing is currently lacking. We addressed this shortcoming by using an eye-tracking method based on gaze-contingent stimulus presentation (Van Belle et al., 2010). While participants named numerosities expressed by canonical and non-canonical finger numeral configurations presented in upright or inverted orientations, we selectively impaired analytical or holistic visual perception by respectively masking (in real time) peripheral or focal vision. Our data confirm the results found in literature: canonical configurations are processed faster than non-canonical ones, upright configurations are processed faster than inverted ones and holistic perception is faster than analytical one. Most importantly, we also demonstrate that canonical configurations are impaired by the peripheral mask (i.e. holistic vision hindered) whereas non-canonical ones are impaired by the foveal mask (i.e. analytical vision hindered). These results confirm that the practice of finger numeral configurations modifies not only the way human beings process and represent numerosities but especially the way to visually perceive them.

Task instructions determine the visuo-spatial and verbal-spatial nature of number-space associations

Poster (2014, April)

Evidence for number-space associations comes from the spatial-numerical association of response-codes (SNARC) effect, consisting in faster reaction times (RTs) to small/large digits with the left/right hand respectively. Classically, they are thought to result from numerical coding along a left-to-right-oriented mental number line (visuo-spatial account; Dehaene et al., 1993). Recently, an association between the verbal concepts “small”/“left” and “large”/“right” has been suggested as an alternative explanation (verbal-spatial account; Gevers et al., 2010). Since the predominance of these accounts remains debated, we aimed to determine whether task instructions influence their extent of explaining the SNARC effect. A magnitude comparison task where the verbal labels “left”/“right” were displayed on the left/right response side alternatively allowed us to directly contrast the two accounts by comparing verbal SNARC slopes (based on differences in RTs to the labels “left” and “right”) with classical spatial SNARC slopes (based on differences in RTs to the left and right response side). In the verbal condition, participants (41 students, 20 female, mean age=21.6) responded to the assigned labels irrespective of their side of appearance, whereas the spatial condition required responding to the left or right response side irrespective of the displayed label. Under verbal instructions, only the verbal slope was significantly negative (verbal slope=-67.54, spatial slope=-4.82). Conversely, no significant difference was observed between verbal and spatial slopes under spatial instructions – both slopes being significantly negative (verbal slope=-15.12, spatial slope=-29.39). Taken together, number-space associations arise from verbal coding regardless of task instructions, while spatial coding only occurs under spatial instructions.

Face perception is tuned to horizontal orientation in the N170 time window

in Journal of Vision (2014), 14(2), 1-18

The specificity of face perception is thought to reside both in its dramatic vulnerability to picture-plane inversion and its strong reliance on horizontally oriented image content. Here we asked when in the visual processing stream face-specific perception is tuned to horizontal information. We measured the behavioral performance and scalp event-related potentials (ERP) when participants viewed upright and inverted images of faces and cars (and natural scenes) that were phase- randomized in a narrow orientation band centered either on vertical or horizontal orientation. For faces, the magnitude of the inversion effect (IE) on behavioral discrimination performance was significantly reduced for horizontally randomized compared to vertically or nonrandomized images, confirming the importance of horizontal information for the recruitment of face- specific processing. Inversion affected the processing of nonrandomized and vertically randomized faces early, in the N170 time window. In contrast, the magnitude of the N170 IE was much smaller for horizontally randomized faces. The present research indicates that the early face- specific neural representations are preferentially tuned to horizontal information and offers new perspectives for a description of the visual information feeding face- specific perception.

Waat as Dyscalculie?

Conference given outside the academic context (2014)

Language influences number processing: the case of bilingual Luxembourg

Scientific Conference (2014)

Discrimination of Numerosities in children studied by means of Fast Periodic Visual Stimulation

Poster (2014)

We are constantly dealing with quantities in our environment. This ability to process numerical magnitude is present in infants (Izard et al., 2009), a variety of animal species (Flombaum et al., 2005) and in tribes with small number words lexicon (Pica et al., 2004). It implies that our brain is able to extract the total number of items in a scene, regardless of perceptual interference (non-numerical properties of the stimuli). However, this ability seems to be refined through development (Halberda et al., 2012), due to visual-perception maturation and/or educational environment, e.g. when learning arithmetic. Here, we measured rapidly and objectively 6-to-12-y.o. children’s sensitivity to (non-)symbolic numerical stimuli (dots or Arabic numbers), using fast periodic visual stimulation (FVPS) as implemented in a repetition-suppression paradigm (Rossion & Boremanse, 2011). Children were presented with stimuli appearing at 3.5 items/second (fundamental frequency=3.5 Hz), for 60 seconds. Half of the sequences consisted of different stimuli at every cycle of stimulation (e.g., “10”, “18”, “12”,...), the other half of sequences were composed of same stimuli (“10”) repeated throughout the whole sequence. We observed a large increase of the EEG response at the fundamental frequency (a steady-state visual evoked potential; Regan, 1966) over the lateral parieto-occipital electrodes sites. This response was reduced when the same stimulus was repeated, especially for symbolic stimuli. These results are correlated to children’s age and visual-perception, arithmetic and non-symbolic numerical abilities (L-POST, KRT, Panamath). They indicate that FPVS of (non-)symbolic numerosities is a promising tool to study children’s sensitivity to numerical magnitude.

The influence of body motion on random number generation

Poster (2014)

Knowledge and thinking are constrained by sensory-motor processes. This increasingly influential view has been termed the “embodiment theory” and proposes that bodily actions directly impact the quality of mental representations. The present study specifically aimed to investigate the influence of passive whole-body movement on numerical cognition. Two recent studies (Loetscher, et al., 2008; Hartmann, et al. 2011) indeed indicate that head or body movements can induce a shift of the attention on the mental number line. More precisely, leftward movements seemed to enhance small number generation while rightward movements led to larger number generation. The current study investigated this effect by using a non-motorized rotating chair. Concretely, while seated, participants were cyclically rotated 40 times for a movement amplitude of 90° from left to right and vice versa at an average frequency of 0.3 Hz. During each 90° movement segment they had to randomly produce numbers ranging between 1 and 30, but for methodological reasons the six extreme numbers were excluded from the analysis. The results indicate that the average number produced during leftward movement was smaller than the average number produced during rightward movement. These findings confirm the impact of passive whole-body movement on the production of numerical stimuli, indicating that rotation-movements of the body can displace attention on the mental number line.

Developing number–space associations: SNARC effects using a color discrimination task in 5-year-olds

in Journal of Experimental Child Psychology (2013), 116

Human adults’ numerical representation is spatially oriented; consequently, participants are faster to respond to small/large numerals with their left/right hand, respectively, when doing a binary classification judgment on numbers, known as the SNARC (spatial– numerical association of response codes) effect. Studies on the emergence and development of the SNARC effect remain scarce. The current study introduces an innovative new paradigm based on a simple color judgment of Arabic digits. Using this task, we found a SNARC effect in children as young as 5.5 years. In contrast, when preschool children needed to perform a magnitude judgment task necessitating exact number knowledge, the SNARC effect started to emerge only at 5.8 years. Moreover, the emergence of a magnitude SNARC but not a color SNARC was linked to proficiency with Arabic digits. Our results suggest that access to a spatially oriented approximate magnitude representation from symbolic digits emerges early in ontogenetic development. Exact magnitude judgments, on the other hand, rely on experience with Arabic digits and, thus, necessitate formal or informal schooling to give access to a spatially oriented numerical representation.

Estimation abilities of large numerosities in preschool children

Poster (2013, October)

The approximate number system (ANS) is thought to be a building block for the elaboration of formal mathematics. However, little is known about how this core system develops and if it can be influenced by external factors at a young age (before the child enters formal numeracy education). The purpose of this study was to examine numerical magnitude representations of 5-6 year old children at 2 different moments of Kindergarten considering children's early number competence as well as schools' socio-economic index (SEI). This study investigated estimation abilities of large numerosities using symbolic and non-symbolic output formats (8-64). In addition, we assessed symbolic and non-symbolic early number competence (1-12) at the end of the 2nd (N = 42) and the 3rd (N = 32) Kindergarten grade. By letting children freely produce estimates we observed surprising estimation abilities at a very young age (from 5 year on) extending far beyond children's symbolic explicit knowledge. Moreover, the time of testing has an impact on the ANS accuracy since 3rd Kindergarteners were more precise in both estimation tasks. Additionally, children who presented better exact symbolic knowledge were also those with the most refined ANS. However, this was true only for 3rd Kindergarteners who were a few months from receiving math instructions. In a similar vein, higher SEI positively impacted only the oldest children's estimation abilities whereas it played a role for exact early number competences already in 2nd and 3rd graders. Our results support the view that approximate numerical representations are linked to exact number competence in young children before the start of formal math education and might thus serve as building blocks for mathematical knowledge. Since this core number system was also sensitive to external components such as the SEI this implies that it can most probably be targeted and refined through specific educational strategies from preschool on.

Estimation abilities of large numerosities in Kindergartners

in Frontiers in Psychology (2013), 4

The approximate number system (ANS) is thought to be a building block for the elaboration of formal mathematics. However, little is known about how this core system develops and if it can be influenced by external factors at a young age (before the child enters formal numeracy education). The purpose of this study was to examine numerical magnitude representations of 5-6 year old children at 2 different moments of Kindergarten considering children's early number competence as well as schools' socio-economic index (SEI). This study investigated estimation abilities of large numerosities using symbolic and non-symbolic output formats (8-64). In addition, we assessed symbolic and non-symbolic early number competence (1-12) at the end of the 2nd (N = 42) and the 3rd (N = 32) Kindergarten grade. By letting children freely produce estimates we observed surprising estimation abilities at a very young age (from 5 year on) extending far beyond children's symbolic explicit knowledge. Moreover, the time of testing has an impact on the ANS accuracy since 3rd Kindergarteners were more precise in both estimation tasks. Additionally, children who presented better exact symbolic knowledge were also those with the most refined ANS. However, this was true only for 3rd Kindergarteners who were a few months from receiving math instructions. In a similar vein, higher SEI positively impacted only the oldest children's estimation abilities whereas it played a role for exact early number competences already in 2nd and 3rd graders. Our results support the view that approximate numerical representations are linked to exact number competence in young children before the start of formal math education and might thus serve as building blocks for mathematical knowledge. Since this core number system was also sensitive to external components such as the SEI this implies that it can most probably be targeted and refined through specific educational strategies from preschool on.

The influence of language on exact additions in bilinguals.

Scientific Conference (2013, May)

To which degree is language involved in arithmetic and dependent on language proficiency? We investigated this question in a German-French educational bilingual setting in Luxembourg, where there is a progressive transition from German to French as a teaching language. Due to this shift, students become increasingly more proficient in the non-dominant language (French) throughout the school years. Interestingly, the decades and units of two-digit number names follow the unit-decade order in German but the decade-unit order in French. Students from grades 7, 8, 10, 11, and German-French adults (total N = 200) solved simple and complex additions presented in different conditions: (1) visual Arabic digits, (2) auditory presentation, and (3) as a dual task in which visually presented additions were preceded by visually presented semantic judgements to indirectly activate a language context. Participants performed each condition in a German and a French testing session. Participants were asked to respond orally in the testing language. Measures include correct responses and response times. The results suggest that language proficiency is crucial for the computation of complex additions, whereas simple additions can be retrieved equally well in both languages. Furthermore, additional error analyses showed more errors on the decade or on the unit digit depending on the language of the task. However, providing a language context seems to enhance performances only in the non-dominant language. Taken together, these results support the view of a strong language influence on arithmetic.

The impact of inhibition capacities on number-space associations

Poster (2013, March 01)

Numerical and spatial representations are tightly linked (for a review see de Hevia et al., 2008). One specific instance of this link is the finding that when doing a binary classification judgment on single Arabic digits, participants are faster to respond with their left/right hand to small/large numbers respectively. This observation has first been described by Dehaene and colleagues in the early 1990’s (Dehaene et al., 1993) and termed the SNARC effect (Spatial Numerical Association of Response Codes). Celebrating its 20th anniversary this year, the SNARC effect has been extensively replicated (for a meta-analysis see Wood et al., 2008) but one of its characteristics remains its high inter-individual variability (Wood et al., 2006a; 2006b). The source of this variability can partly be ascribed to differences in mathematical proficiency (Hoffmann et al., submitted) but a more domain general hypothesis implicating general inhibition capacities warrants further investigation. For the present study a total of 77 participants have been evaluated with a SNARC paradigm as well as standard inhibition tests (Stroop, Incompatibility subtest of the TAP test). Results show that when age-appropriate inhibition tests are used, inhibition capacities are strongly correlated with the SNARC effect, in the way that very efficient inhibition capacities lead to weaker SNARC effects. Consequently this finding could at least partly explain the impact of arithmetical proficiency on the SNARC effect. A study combining both measures would be an appropriate next step.

Estimation abilities of large numerosities in preschool children: Do they depend on school grade and socio-economic background?

Poster (2013, March 01)

The approximate number system (ANS) is thought to be a building block for the elaboration of formal mathematics. However, little is known about how this core system develops and if it can be influenced by external factors at a young age (before the child enters formal numeracy education). The purpose of this study was to examine numerical magnitude representations of 5-6 year old children at 2 different moments of Kindergarten considering children's early number competence as well as schools' socio-economic index (SEI). This study investigated estimation abilities of large numerosities using symbolic and non-symbolic output formats (8-64). In addition, we assessed symbolic and non-symbolic early number competence (1-12) at the end of the 2nd (N = 42) and the 3rd (N = 32) Kindergarten grade. By letting children freely produce estimates we observed surprising estimation abilities at a very young age (from 5 year on) extending far beyond children's symbolic explicit knowledge. Moreover, the time of testing has an impact on the ANS accuracy since 3rd Kindergarteners were more precise in both estimation tasks. Additionally, children who presented better exact symbolic knowledge were also those with the most refined ANS. However, this was true only for 3rd Kindergarteners who were a few months from receiving math instructions. In a similar vein, higher SEI positively impacted only the oldest children's estimation abilities whereas it played a role for exact early number competences already in 2nd and 3rd graders. Our results support the view that approximate numerical representations are linked to exact number competence in young children before the start of formal math education and might thus serve as building blocks for mathematical knowledge. Since this core number system was also sensitive to external components such as the SEI this implies that it can most probably be targeted and refined through specific educational strategies from preschool on.

Sensitivity to spacing information increases more for the eye region than for the mouth region during childhood

in International Journal of Behavioral Development (2013), 37(2), 169-174

Sensitivity to spacing information within faces improves with age and reaches maturity only at adolescence. In this study, we tested 6–16-year-old children’s sensitivity to vertical spacing when the eyes or the mouth is the facial feature selectively manipulated. Despite the similar discriminability of these manipulations when they are embedded in inverted faces (Experiment 1), children’s sensitivity to spacing information manipulated in upright faces improved with age only when the eye region was concerned (Experiment 2). Moreover, children’s ability to process the eye region did not correlate with their selective visual attention, marking the automation of the mechanism (Experiment 2). In line with recent findings, we suggest here that children rely on a holistic/configural face processing mechanism to process the eye region, composed of multiple features to integrate, which steadily improves with age.

The impact of inhibition capacities on number-space associations in young and elderly adults

Poster (2013, February 26)

Background: Numerical and spatial representations are tightly linked, i.e. when doing a binary classification judgment on Arabic digits participants are faster to respond with their left/right hand to small/large numbers respectively (SNARC effect, Dehaene et al., 1993). The SNARC effect has been extensively replicated but one of its characteristics remains inter-individual variability (Wood et al., 2006). Different sources have been proposed to account for the reported inter-individual variability, namely response speed (Gevers et al., 2006), inhibition capacities (Wood et al., 2008) and age (Wood et al., 2008). The present study aims to investigate the impact of inhibition capacities on the SNARC effect in young and elderly adults, controlling for individual general processing speed. Methods: Two groups of participants were included: young adults, N=28, mean age: 23 years (SD=3.02) and elderly adults, N=46, mean age: 65.9 years (SD=3.9). Participants performed a parity judgment SNARC paradigm as well as inhibition tests (Stroop, Incompatibility). General processing speed was evaluated using a simple shape matching task. Results: The two age-groups differed in the strength of the SNARC effect, inhibition capacities and processing speed, with the elderly adults displaying stronger SNARC effects, weaker inhibition capacities and slower processing speed. Correlation analysis including all participants confirmed these findings on an individual level by showing relations between the SNARC effect and age, as well as relations between the SNARC effect and both inhibition capacities (i.e. the Stroop effect) and processing speed. When controlling for processing speed, the relations between the SNARC effect and both inhibition capacities and age remained. Conversely, when controlling for inhibition capacities, only the relation between the SNARC effect and age (but not processing speed) remained significant, even when controlling in addition for processing speed. Relevance: By combining the variables age, inhibition capacities and individual processing speed, the present data are the first to reveal a strong link between inhibition capacities and number-space associations. Importantly, we demonstrate that this link is not mediated by general processing speed. Interestingly, the robust relation between the SNARC effect and age remains after controlling for processing speed and inhibition capacities, pointing to a new source of inter-individual differences in the strength of the SNARC effect that will need to be clarified in future research projects.

Estimation abilities of large numerosities in Kindergartners.

in Frontiers in psychology (2013), 4

The approximate number system (ANS) is thought to be a building block for the elaboration of formal mathematics. However, little is known about how this core system develops and if it can be influenced by external factors at a young age (before the child enters formal numeracy education). The purpose of this study was to examine numerical magnitude representations of 5-6 year old children at 2 different moments of Kindergarten considering children's early number competence as well as schools' socio-economic index (SEI). This study investigated estimation abilities of large numerosities using symbolic and non-symbolic output formats (8-64). In addition, we assessed symbolic and non-symbolic early number competence (1-12) at the end of the 2nd (N = 42) and the 3rd (N = 32) Kindergarten grade. By letting children freely produce estimates we observed surprising estimation abilities at a very young age (from 5 year on) extending far beyond children's symbolic explicit knowledge. Moreover, the time of testing has an impact on the ANS accuracy since 3rd Kindergarteners were more precise in both estimation tasks. Additionally, children who presented better exact symbolic knowledge were also those with the most refined ANS. However, this was true only for 3rd Kindergarteners who were a few months from receiving math instructions. In a similar vein, higher SEI positively impacted only the oldest children's estimation abilities whereas it played a role for exact early number competences already in 2nd and 3rd graders. Our results support the view that approximate numerical representations are linked to exact number competence in young children before the start of formal math education and might thus serve as building blocks for mathematical knowledge. Since this core number system was also sensitive to external components such as the SEI this implies that it can most probably be targeted and refined through specific educational strategies from preschool on.

Investigating the links between spatial-numerical interactions and sequence processing using patterned TMS

Poster (2013)

Number-space interactions and how they develop over lifespan

Presentation (2012, December 05)

Attentional shifts induced by uninformative number symbols modulate neural activity in human occipital cortex

in Neuropsychologia (2012), 50

Number processing interacts with space encoding in a wide variety of experimental paradigms. Most intriguingly, the passive viewing of uninformative number symbols can shift visuo-spatial attention to different target locations according to the number magnitude, i.e., small/large numbers facilitate processing of left/right targets, respectively. The brain architecture dedicated to these attention shifts associated with numbers remains unknown. Evoked potential recordings indicate that both early and late stages are involved in this spatio-numerical interaction, but the neuro-functional anatomy needs to be specified. Here we use, for the first time, functional magnetic resonance imaging (fMRI) to investigate attentional orienting following uninformative Arabic digits. We show that BOLD response in occipital visual regions is modulated by the congruency between digit magnitude (small/large) and target side (left/right). Additionally, we report higher BOLD responses following large (8, 9) compared to small (1, 2) digits in two bilateral parietal regions, yielding a significant effect of digit magnitude. We propose and discuss the view that encoding of semantic representations related to number symbols in parietal cortex leads to shifts in visuo-spatial attention and enhances visual processing in the occipital cortex according to number-space congruency rules.

LEARN stellt sech fier

E-print/Working paper (2012)

A developmental investigation of the SNARC effect using a colour discrimination task.

Presentation (2012, July 17)

How do number-space interactions develop from childhood to adulthood? The SNARC effect (Spatial Numerical Association of Response Codes) reflects the finding that participants respond faster to small numbers with their left hand and to large numbers with their right hand during a number classification task. Typically assessed through magnitude-independent parity judgment tasks, the SNARC effect is thought to show the automaticity of the number-space link. Using a parity task on children Berch et al. (1999) found a SNARC effect no earlier than from 9.2 years onwards. However, we hypothesise that parity judgments might be inappropriate to assess younger children. Therefore a more age-apropriate colour judgment task (implicit) and a magnitude judgement task (explicit) were designed and tested on 363 children from kindergarten to Grade 6 (5.8-12 years). The experimental tasks were complemented by a brief assessment of arithmetic skills. The results revealed overall significant SNARC effects [colour task t(355)=2.6, p<0.01; magnitude task t(340)=4.7, p<0.001], which interacted with grade [colour task F(6,355)=2.18; p<0.05; magnitude task F(6,340)=2.09; p=0.05]. Most interestingly, even the kindergartners already display both effects [colour task t(28)=1.96; p<0.05; magnitude task t(24)=1.7; p=0.05]. These results show explicit and implicit access to numerical magnitude in children as young as 5.8 years.

Attentional shifts induced by uninformative number symbols modulate neural activity in human occipital cortex

Presentation (2012, July 17)

Number processing interacts with space encoding in a wide variety of experimental paradigms. Most intriguingly, the passive viewing of uninformative number symbols can shift visuo-spatial attention to different target locations according to the number magnitude, i.e. small/large numbers facilitate processing of left/right targets, respectively. The brain architecture dedicated to these attention shifts associated with numbers currently remains unknown. Evoked potential recordings indicate that both early and late stages are involved in this spatio-numerical interaction, but the neuro-functional anatomy needs to be specified. Here we use, for the first time, functional magnetic resonance imaging (fMRI) to investigate attentional orienting following uninformative Arabic digits. We show that BOLD response in occipital visual regions was modulated by the congruency between digit magnitude (small/large) and target side (left/right). Additionally, we report higher BOLD responses following large (8, 9) compared to small (1, 2) digits in two bilateral parietal regions, yielding a significant effect of digit magnitude. We propose and discuss the view that automatic encoding of semantic representations related to number symbols in parietal cortex lead to shifts in visuo-spatial attention and enhanced visual processing in the occipital cortex according to number-space congruency rules.

Number and space interact. But how are they influenced by cognitive development and math education?

Presentation (2012, May 23)

Do the mental number line and spatial sequence synesthesia share neural substrates? A patterned TMS study.

Poster (2012, May)

Differences between Dyscalculic children, Typical Children and Adults during a Visuo-Spatial and Addition task

Presentation (2012, February 17)

Shifts of spatial attention cued by irrelevant numbers: Electrophysiological evidence from a target discrimination task

Poster (2012, February 10)

Fischer et al. demonstrated that a centrally presented number can shift attention to the left/right when its magnitude is small/large. Two electrophysiological studies described these attentional effects as event-related potentials (ERPs) at centro-parietal sites. Since both studies used target detection tasks, it remains currently unknown whether similar results would be obtained with a discrimination task. We used ERPs to test whether digit cues also induce attention shifts when participants perform a feature-discrimination task on targets. ERPs were recorded whereas subjects discriminated the colour of lateral targets that were preceded by a central non-predictive digit. Analysis of cue-locked controlateral vs. ipsilateral ERP activity showed the emergence of early preparatory attention-directing components in parietal and frontal regions. Moreover, target-locked P1 components at occipito-parietal sites were significantly modulated by digit magnitude-target side congruency. These results demonstrate that irrelevant digit cues also bias sensory processing when embedded in a feature-discrimination task.

Local discriminability determines the strength of holistic processing for faces in the fusiform face area.

in Frontiers in psychology (2012), 3

Recent evidence suggests that the Fusiform Face Area (FFA) is not exclusively dedicated to the interactive processing of face features, but also contains neurons sensitive to local features. This suggests the existence of both interactive and local processing modes, consistent with recent behavioral findings that the strength of interactive feature processing (IFP) engages most strongly when similar features need to be disambiguated. Here we address whether the engagement of the FFA into interactive versus featural representational modes is governed by local feature discriminability. We scanned human participants while they matched target features within face pairs, independently of the context of distracter features. IFP was operationalized as the failure to match the target without being distracted by distracter features. Picture-plane inversion was used to disrupt IFP while preserving input properties. We found that FFA activation was comparably strong, irrespective of whether similar target features were embedded in dissimilar contexts(i.e., inducing robust IFP) or dissimilar target features were embedded in the same context (i.e., engaging local processing). Second, inversion decreased FFA activation to faces most robustly when similar target features were embedded in dissimilar contexts, indicating that FFA engages into IFP mainly when features cannot be disambiguated at a local level. Third, by means of Spearman rank correlation tests, we show that the local processing of feature differences in the FFA is supported to a large extent by the Occipital Face Area, the Lateral Occipital Complex, and early visual cortex, suggesting that these regions encode the local aspects of face information. The present findings confirm the co-existence of holistic and featural representations in the FFA. Furthermore, they establish FFA as the main contributor to the featural/holistic representational mode switches determined by local discriminability.

A developmental investigation of the SNARC effect using a colour discrimination task.

Poster (2012)

How do number-space interactions develop from childhood to adulthood? The SNARC effect (Spatial Numerical Association of Response Codes) reflects the finding that participants respond faster to small numbers with their left hand and to large numbers with their right hand during a number classification task. Typically assessed through magnitude-independent parity judgment tasks, the SNARC effect is thought to show the automaticity of the number-space link. Using a parity task on children Berch et al. (1999) found a SNARC effect no earlier than from 9.2 years onwards. However, we hypothesise that parity judgments might be inappropriate to assess younger children. Therefore a more age-appropriate colour judgment task (implicit) and a magnitude judgement task (explicit) were designed and tested on 363 children from kindergarten to Grade 6 (5.8-12 years). The experimental tasks were complemented by a brief assessment of arithmetic skills. The results revealed overall significant SNARC effects [colour task t(355)=2.6, p<0.01; magnitude task t(340)=4.7, p<0.001], which interacted with grade [colour task F(6,355)=2.18; p<0.05; magnitude task F(6,340)=2.09; p=0.05]. Most interestingly, even the kindergartners already display both effects [colour task t(28)=1.96; p<0.05; magnitude task t(24)=1.7; p=0.05]. These results show explicit and implicit access to numerical magnitude in children as young as 5.8 years.

Le cerveu à l`école

Conference given outside the academic context (2011)

Scrambling horizontal face structure: behavioral and electrophysiogical evidence for a tuning of visual face processing to horizontal information

Poster (2011, August)

Filtering faces to remove all but the horizontal information largely preserves behavioral signatures of face-specific processing, including the face inversion effect (FIE). Conversely, preserving only vertical information abolishes this effect. In contrast to previous studies which used filtering, the present studies manipulated orientation content of face images by randomizing Fourier phase spectrum in a narrow horizontal orientation band (H-randomization) or vertical orientation band (V-randomization). Phase-randomization was performed on face images in which spatial frequency amplitude spectrum (SF-AS) was either left unaltered or equalized across all SF orientations. We further investigated the time course of horizontal tuning using event-related potentials (ERP). We observed that (i) upright faces were best discriminated when the horizontal structure was preserved (ie V-randomization) compared to H-randomization; (ii) this phase-randomization effect was eliminated by inversion, resulting in (iii) a smaller FIE for H-randomized than V-randomized faces. This pattern was still present but was less consistent when SF-AS was equalized across SF orientations, suggesting that SF-AS in horizontal orientation contributes to the horizontal tuning of face perception. ERP evidence of horizontal tuning for upright face processing was observed in the N170 time-window, a well-known face-sensitive electrophysiological component. The N170 was delayed for H-randomized compared to V-randomized faces. Additionally, and in line with behavioural data, face inversion increased N170 latency to a smaller extent for H-randomized compared to V-randomized. Altogether, our findings indicate that horizontal tuning is a robust property of face perception that arises early in high-level visual cortex.

Interactions between number and space processing in adults with dyscalculia

Poster (2011, May 27)

A large body of evidence indicates clear relationships between number and space processing in healthy and brain-damaged adults, as well as in children. The present paper addressed this issue regarding atypical math development. Adults with a diagnosis of dyscalculia (DYS) during childhood were compared to adults with average or high abilities in mathematics across two bisection tasks. Participants were presented with Arabic number triplets and had to judge either the number magnitude or the spatial location of the middle number relative to the two outer numbers. For the numerical judgment, adults with DYS were slower than both groups of control peers. They were also more strongly affected by the factors related to number magnitude such as the range of the triplets or the distance between the middle number and the real arithmetical mean. By contrast, adults with DYS were as accurate and fast as adults who never experienced math disability when they had to make a spatial judgment. Moreover, number-space congruency affected performance similarly in the three experimental groups. These findings support the hypothesis of a deficit of number magnitude representation in DYS with a relative preservation of some spatial mechanisms in DYS. Results are discussed in terms of direct and indirect number-space interactions.

Contribution of Spatial Frequency and Orientation to upright and inverted face perception

Poster (2011, May)

It was recently shown that expert face perception relies on the extraction of horizontally oriented visual cues. Picture-plane inversion was found to eliminate horizontal, suggesting that this tuning contributes to the specificity of face processing. The present experiments sought to determine the spatial frequency (SF) scales supporting the horizontal tuning of face perception. Participants were instructed to match upright and inverted faces that were filtered both in the frequency and orientation domains. Faces in a pair contained horizontal or vertical ranges of information in low, middle, or high SF (LSF, MSF, or HSF). Our findings confirm that upright (but not inverted) face perception is tuned to horizontal orientation. Horizontal tuning was the most robust in the MSF range, next in the HSF range, and absent in the LSF range. Moreover, face inversion selectively disrupted the ability to process horizontal information in MSF and HSF ranges. This finding was replicated even when task difficulty was equated across orientation and SF at upright orientation. Our findings suggest that upright face perception is tuned to horizontally oriented face information carried by intermediate and high SF bands. They further indicate that inversion alters the sampling of face information both in the orientation and SF domains.

Shifts of spatial attention cued by irrelevant numbers: Electrophysiological evidence from a target discrimination task

Poster (2011, April)

Fischer et al. demonstrated that a centrally presented number can shift attention to the left/right when its magnitude is small/large. Two electrophysiological studies described these attentional effects as event-related potentials (ERPs) at centro-parietal sites. Since both studies used target detection tasks, it remains currently unknown whether similar results would be obtained with a discrimination task. We used ERPs to test whether digit cues also induce attention shifts when participants perform a feature-discrimination task on targets. ERPs were recorded whereas subjects discriminated the colour of lateral targets that were preceded by a central non-predictive digit. Analysis of cue-locked controlateral vs. ipsilateral ERP activity showed the emergence of early preparatory attention-directing components in parietal and frontal regions. Moreover, target-locked P1 components at occipito-parietal sites were significantly modulated by digit magnitude-target side congruency. These results demonstrate that irrelevant digit cues also bias sensory processing when embedded in a feature-discrimination task.

When numbers act as attentional cues: behavioral and fMRI investigations

Poster (2011, February 11)

The SNARC effect – Does it depend on the level of mathematical training?

Poster (2011)

Behavioural studies show a relation between numbers and space (DeHevia et al., 2008). One instance of this link is the SNARC (Spatial Numerical Association of Response Codes) effect, consisting in faster reaction times responding to small/large digits with the left/right hand respectively (Dehaene et al. 1993). The SNARC effect has often been replicated, but it is also characterized by high inter-subject variability (Wood et al. 2006a,b). Although differences in mathematical skills are an obvious candidate source for SNARC variability, this variable has not yet been explored systematically. While in their seminal study Dehaene and colleagues had included two groups of participants differing in their field of study (science vs. literature), the differences in SNARC effect strengths indicated by the result figures were not tested formally (see also Fischer and Rottmann (2005)). The present study aims to assess the influence of mathematical training, as instantiated by the enrollment in study fields characterized by distinct levels of mathematical requirements, on the SNARC effect. We only included students of either a subject with a strong mathematical focus (e.g. mathematics, computer sciences), or no mathematical requirements at all (e.g. literature, philosophy). Results (N=36; 18/group) yielded a significant overall SNARC effect, i.e. interaction between digit magnitude and response side [F(1,35)=9.51; p=0.004], but no influence of study group on this interaction [F(1,35)=0.92; p=0.345]. Interestingly though, including gender in the ANOVA yielded a significant four-way interaction [F(1,35)=6.34; p=0.017]. These results replicate previous findings in children (Schweiter et al. 2005), interpreted as gender-related differences in mental strategy use.

Facilitation and inhibition of return using numbers as attentional cues

Poster (2011)

Behavioural studies have shown a relation between numbers and space (DeHevia et al., 2008). Fischer and colleagues (2003) showed that digits can act as central spatial cues in a target detection task, resulting in shorter reaction times (RT) for left-sided targets when preceded by small numbers and for right-sided targets when preceded by large numbers. This facilitation effect indicates that numbers orient visuo-spatial attention to the left or right hemifield, depending on their magnitude. To date no studies investigated whether this facilitation is followed by inhibition of return at longer intervals, as could be expected with visuo-spatial attention shifts. To this aim, we designed an analogous paradigm to Fischer et al.’s, introducing additional longer intervals. Participants (n=25) were presented a task irrelevant digit (1,2 vs. 8,9) for 400ms and had to detect a brief (100ms) lateral target appearing after a variable interval (100, 250, 500, 750, 1000, 1250ms). A 2x6 repeated measures ANOVA of mean RT, with congruency and interval as within-subject variables yielded a significant interaction (F(5,24)=2.3, p<0.05). As expected, targets were detected faster when appearing in the congruent (small-left, large-right) hemifield after 250ms. Using the regression method proposed by Lorch and Myers (1990), the slope at this interval was significantly negative (t(24)=1.70, p=0.05); indicating a facilitation for the detection of targets in the congruent hemifield) (cf. Fischer et al., 2003). At the 1250ms interval, targets were detected significantly slower when they appeared in the congruent compared to the incongruent hemifield (yielding significantly positive slopes at 1250ms: t(24)=2.68, p=0.007). These findings provide the first evidence that digits not only produce facilitation effects at shorter intervals, but also induce inhibitory effects at longer intervals, confirming the visuo-spatial nature of the attention shifts associated with Arabic digits.

Characterizing the face processing network in the human brain: a large-scale fMRI localizer study

in Journal of Vision (2010), 10(7),

A whole network of brain areas showing larger response to faces than other visual stimuli has been identified in the human brain using fMRI (Sergent, 1992; Haxby, 2000). Most studies identify only a subset of this network, by comparing the presentation of face pictures to all kinds of object categories mixed up (e.g., Kanwisher, 1997), or to scrambled faces (e.g., Ishaï, 2005), using different statistical thresholds. Given these differences of approaches, the (sub)cortical face network can be artificially overextended (Downing & Wiggett, 2008), or minimized in different studies, both at the local (size of regions) and global (number of regions) levels. Here we conducted an analysis of a large set of right-handed subjects (40), tested with a new whole-brain localizer to control for both high-level and low-level differences between faces and objects. Pictures of faces, cars and their phase-scrambled counterparts were used in a 2x2 block design. Group-level (random effect) and single subject (ROI) analyses were made. A conjunction of two contrasts (F-SF and F-C) identified 6 regions: FFA, OFA, amygdala, pSTS, AIT and thalamus. All these regions but the amygdala showed clear right lateralization. Interestingly, the FFA showed the least face-selective response among the cortical face network: it presented a significantly larger response to pictures of cars than scrambled cars [t=9.3, much more than amygdala (t=2.6), AIT (t=2.1) and other regions (NS)], and was also sensitive to low-level properties of faces [SF - SO; t=5.1; NS in other areas]. These observations suggest that, contrary to other areas of the network, including the OFA, the FFA is a region that may contain populations of neurons that are specific to faces intermixed with populations responding more generally to object categories. More generally, this study helps understanding the extent and specificity of the network of (sub)cortical areas particularly involved in face processing.

Cerebral lateralization of the face-cortical network in left-handers: only the FFA does not get it right

in Journal of Vision (2010), 10(7),

Face processing is a function that is highly lateralized in humans, as supported by original evidence from brain lesion studies (Hecaen & Anguerlergues, 1962), followed by studies using divided visual field presentations (Heller & Levy, 1981), neuroimaging (Sergent et al., 1992) and event-related potentials (Bentin et al., 1996). Studies in non-human primates (Perrett et al., 1988; Zangenehpour & Chaudhuri, 2005), or other mammals (Peirce & Kendrick, 2001) support the right lateralization of the function, which may be related to a dominance of the right hemisphere in global visual processing. However, in humans there is evidence that manual preference may shift or qualify the pattern of lateralization for faces in the visual cortex: face recognition impairments following unilateral left hemisphere brain damage have been found only in a few left-handers (e.g., Mattson et al., 1992; Barton, 2009). Here we measured the pattern of lateralization in the entire cortical face network in right and left-handers (12 subjects in each group) using a well-balanced face-localizer block paradigm in fMRI (faces, cars, and their phase-scrambled versions). While the FFA was strongly right lateralized in right-handers, as described previously, it was equally strong in both hemispheres in left-handers. In contrast, other areas of the face-sensitive network (posterior superior temporal sulcus, pSTS; occipital face area, OFA; anterior infero-temporal cortex, AIT; amygdala) remained identically right lateralized in both left- and right-handers. Accordingly, our results strongly suggest that the face-sensitive network is equally lateralized for left- and right-handers, and thus the face processing is not influenced by handedness. However, the FFA is an important exception since it is right-lateralized for right-handers but its recruitment is more balanced between hemispheres for left-handers. These observations carry important theoretical and clinical implications for the aetiology of brain lateralization depending on the left- or right-handedness and the neuropsychological undertaking of prosopagnosic patients.

When small is left and large is right : Behavioural evidence for attentional shifts due to irrelevant numerical cues

Poster (2010)

Numerous behavioural studies indicate the existence of a link between numerical representations and visuo-spatial processes (for review see DeHevia et al., 2008). A striking demonstration of this link was provided by Fischer and colleagues (2003), who reported that participants detect a target faster in the left hemifield, if preceded by a small number (e.g. 2 or 3) and faster in the right hemifield if preceded by a large number (e.g. 8 or 9). This is strong evidence that numbers orient visuo-spatial attention to the left or right hemifield, depending on their magnitude (e.g., small and large, respectively) (see also Galfano et al., 2006; Ristic et al., 2006). We designed a modified version of this target detection paradigm, by replacing the detection task with a target discrimination task (cf. Hommel et al., 2001). The participants (n=16) were presented 1 task irrelevant digit (1,2 vs. 8,9) for 400ms. After a variable inter-stimulus interval (500, 1000 or 2000ms), they had to discriminate the colour of a brief (100ms) lateral target. We hypothesized that the centrally presented numbers would induce an orientation of attention, in the same direction as the initial observations by Fischer et al. (2003). The current results indicate a significant effect, but only for the shortest digit-target interval (500ms). We observed a significant interaction between number magnitude (small/large) and side of target presentation (left/right) (F1,15 =7.784, p<0.014). These findings indicate that the attentional shifts induced by irrelevant numerical material are independent of the exact nature of target processing (discrimination vs. detection).

Temporal dynamics of face spatial frequency processing: An fmri masking experiment

Poster (2009, May)

When processing a face stimulus, the human visual system tends to strongly integrate its constituent features (eyes, nose, mouth, etc) in a so-called holistic representation. Such feature integration mainly occurs in face-sensitive regions located in bilateral fusiform gyrii. Behavioural studies showed that feature integration relies on the extraction of low spatial frequencies (LSF) while high SF (HSF) underlie more local aspects of feature analysis. Following coarse-to-fine models of vision, we propose that the LSF-driven feature integration is an early and fast stage of face perception, in contrast to the longer-lasting extraction of detailed feature cues in HSF. By means of an event-related fMRI design, the present study investigated the temporal dynamics of face LSF and HSF processing in the network of face-sensitive cortical regions. Faces were flashed at 75, 150, or 300 msec, followed by a Gaussian mask. They were band-pass filtered to preserve low or high SF. At short stimulus durations, face-sensitive regions located in bilateral fusiform gyrii and superior temporal sulci responded more strongly to LSF than HSF faces. At longer durations, the same regions were more active for HSF than LSF faces. This pattern did not replicate for phase-scrambled versions of the stimuli. Taken together our findings suggest that face perception proceeds following a coarse-to-fine scenario, with an early and fast LSF-driven feature integration being relayed by the slower accumulation of HSF local information.

Relations between numerical and visuospatial competencies

Scientific Conference (2009)

The roles of "face" and "non-face" areas during individual face perception: Evidence by fmri adaptation in a brain-damaged prosopagnosic patient

in NeuroImage (2008), 40(1), 318-332

Two regions in the human occipito-temporal cortex respond preferentially to faces: 'the fusiform face area' ('FFA') and the 'occipital face area' ('OFA'). Whether these areas have a dominant or exclusive role in face perception, or if sub-maximal responses in other visual areas such as the lateral occipital complex (LOC) are also involved, is currently debated. To shed light on this issue, we tested normal participants and PS, a well-known brain-damaged patient presenting a face-selective perception deficit (prosopagnosia) [Rossion, B., Caldara, R., Seghier, M., Schuller, A. M., Lazeyras, F., Mayer, E. (2003). A network of occipito-temporal face-sensitive areas besides the right middle fusiform gyrus is necessary for normal face processing. Brain 126 2381-2395.], with functional magnetic resonance imaging (fMRI). Of particular interest, the right hemisphere lesion of the patient PS encompasses the 'OFA' but preserves the 'FFA' and LOC [Sorger, B., Goebel, R., Schiltz, C., Rossion, B. (2007). Understanding the functional neuroanatomy of acquired prosopagnosia. NeuroImage 35, 836-852.]. Using fMRI-adaptation, we found a dissociation between the coding of individual exemplars in the structurally intact 'FFA', which was impaired for faces but preserved for objects in the patient PS's brain. Most importantly, a larger response to different faces than repeated faces was found in the ventral part of the LOC both for normals and the patient, next to the right hemisphere lesion. Thus, following prosopagnosia, areas that do not respond preferentially to faces such as the ventral part of the LOC (vLOC) may still be recruited for compensatory or residual individual face perception. Overall, these observations indicate that several high-level visual areas in the human brain contribute to individual face perception. However, a subset of these areas in the right hemisphere, those responding preferentially to faces ('FFA' and 'OFA'), appear to be critical for this function.

Is there continuity between categorical and coordinate spatial relations coding? Evidence from a grid/no-gridworking memory paradigm

in Neuropsychologia (2008), 46(2), 576-594

We ask the question whether the coding of categorical versus coordinate spatial relations depends on different neural networks showing hemispheric specialization or whether there is continuity between these two coding types. The `continuous spatial coding' hypothesis would mean that the two coding types rely essentially on the same neural network consisting of more general-purpose processes, such as visuo-spatial attention, but with a different weighting of these general processes depending on exact task requirements. With event-related fMRI, we have studied right-handed male subjects performing a grid/no-grid visuo-spatial working memory task inducing categorical and coordinate spatial relations coding. Our data support the `continuous spatial coding' hypothesis, indicating that, while based on the same fronto-parieto-occipital neural network than categorical spatial relations coding, the coding of coordinate spatial relations relies more heavily on attentional and executive processes, which could induce hemispheric differences similar to those described in the literature. The results also show that visuo-spatial working memory consists of a short-term posterior store with a capacity of up to three elements in the parietal and extrastriate cortices. This store depends on the presence of a visible space categorization and thus can be used for the coding of categorical spatial relations. When no visible space categorization is given or when more than three elements have to be coded, additional attentional and executive processes are recruited, mainly located in the dorso-lateral prefrontal cortex.

The spatio-temporal correlates of holistic face perception

Poster (2007, May)

It is well known that faces are perceived holistically: their parts are integrated into a global or so-called holistic individual representation. Here we clarify where and how early in time individual holistic representations are extracted from the visual stimulus, by means of an event-related identity adaptation paradigm in fMRI (study 1; 10 subjects) and ERPs (study 2; 16 subjects). During blocks, subjects were presented with trials made of two sequentially presented faces and performed a same/different judgement on the top parts of each pair of faces. Face parts were presented either aligned or misaligned. For each face pair, the identity of top and bottom parts could be (a) both identical, (b) both different, (c) different only for the bottom part. The latter manipulation resulted in a strong face composite illusion behaviourally, i.e. the perception of identical top parts as being different, only in the aligned format. In the face-sensitive area of the middle fusiform gyrus (‘fusiform face area’) we observed a stronger response to the top part perceived as being different (release from adaptation), but only when the top and the bottom parts were aligned. It is consistent with the illusion of viewing different top parts of faces, and this release from fMR-adaptation is similar to the one observed in the ‘different’ condition for both aligned and misaligned parts. The same observations were made in ERPs as early as 150 ms, the amplitude of the electrophysiological response at occipito-temporal sites to the second face stimulus being reduced for identical relative to different top face parts, and to identical top parts perceived as different (aligned - bottom different). With both methods, the effects were stronger in the right hemisphere. Altogether, these observations indicate that individual faces are perceived holistically as early as 150 ms in the occipito-temporal cortex.

Fmri evidence for multiple face processing pathways in the human brain

Poster (2007, May)

Two regions in the occipito-temporal cortex respond more strongly to faces than to objects and are thought to be important for face perception: ‘the fusiform face area’ (‘FFA’) and the ‘occipital face area’ (‘OFA’). Whether these areas responding preferentially to faces play a dominant or exclusive role in face processing or if sub-maximal responses in other areas of the ventral stream such as the lateral occipital complex (LOC) are also involved is currently debated. To clarify this issue, we tested a brain-damaged patient presenting a face-selective deficit, prosopagnosia, with functional magnetic resonance imaging (fMRI). Using fMRI-adaptation, we found a dissociation between the coding of identity in the structurally intact ‘FFA’, which was impaired for faces but preserved for objects. This observation complements recent fMRI findings that the ‘FFA’ reflects averaging of heterogeneous highly selective neural populations for faces and objects, by showing here that the responses of these populations can be functionally independent. Most importantly, a larger response to different faces than repeated faces was found in the ventral part of the LOC both for normals and the patient, next to the right hemisphere lesion. Following prosopagnosia, areas that do not respond preferentially to faces such as the ventral part of the LOC (vLOC) may still be recruited to subtend residual individual face discrimination. Overall, these observations indicate that faces are processed through a network of visual areas in the human brain, with a subset of these areas responding preferentially to faces being critical for efficient face recognition.

Visuelle Wahrnehmung und arithmetische Kompetenzen

in Motorik (2007), 4

Numerical competencies of young children

Scientific Conference (2007)

Numerous studies show that wide ranges of competencies in different fields are necessary to develop a good numerical competency. Our research tried to find an answer to the question, which out of various factors mainly influence the numerical competencies of young children. We focused on visuospatial, perceptive and tactile skills as determinants of the quality of early numerical representations. We adopted a longitudinal research design with three periods of data collection (two data collections during the second year of kindergarten and one at the end of first grade). Our test setting for the kindergarten included tests in the three areas mentioned above. The evaluation of these results shows that the numerical competencies are influenced by visuospatial competencies and knowledge of pre-numerical facts. An importance of the perceptive and tactile skills could not be established. At the end of first grade, after formal mathematical instruction, we made a mathematical competency test. A structural equation model of the subtests shows that the numerical knowledge at this stage can be divided in two separate factors: 1. A representational numerical factor (analogical representation of quantities: Triple Code model of Dehaene) 2. A more formal knowledge of mathematics (visual Arabic representation: Triple Code model of Dehaene, 1992). Predicting these two factors from the competency profile measured in kindergarten showed that the representational numerical factor was very well predicted from a general spatio-numerical factor found in the previous year, while the formal knowledge was predicted to a lesser degree by tactile skills measured at the end of kindergarten. Implications for numerical teaching in Kindergarten will be discussed.

Preserved individual face discrimination in the ventral lateral occipital complex (vloc) of a brain-damaged prosopagnosic patient

Scientific Conference (2006, June 17)

Impaired face discrimination in acquired prosopagnosia is associated with abnormal response to individual faces in the right middle fusiform gyrus

in Cerebral Cortex (2006), 16(4), 574-586

The middle fusiform gyrus (MFG) and the inferior occipital gyrus (IOG) are activated by both detection and identification of faces. Paradoxically, patients with acquired prosopagnosia following lesions to either of these regions in the right hemisphere cannot identify faces, but can still detect faces. Here we acquired functional magnetic resonance imaging (fMRI) data during face processing in a patient presenting a specific deficit in individual face recognition, following lesions encompassing the right IOG. Using an adaptation paradigm we show that the fMRI signal in the rMFG of the patient, while being larger in response to faces as compared to objects, does not differ between conditions presenting identical and distinct faces, in contrast to the larger response to distinct faces observed in controls. These results suggest that individual discrimination of faces critically depends on the integrity of both the rMFG and the rIOG, which may interact through re-entrant cortical connections in the normal brain.

Recovery from adaptation to facial identity is larger for upright than inverted faces in the human occipito-temporal cortex

in Neuropsychologia (2006), 44(6), 912-922

Human faces look more similar to each other when they are presented upside-down, leading to an increase of error rates and response times during individual face discrimination tasks. Here we used functional magnetic resonance imaging (fMRI) to test the hypothesis that this perceived similarity leads to a lower recovery from identity adaptation for inverted faces than for upright faces in face-sensitive areas of the occipito-temporal cortex. Ten subjects were presented with blocks of upright and inverted faces, with the same face identity repeated consecutively in half of the blocks, and different facial identities repeated in the other blocks. When face stimuli were presented upright, the percent signal change in the bilateral middle fusiform gyrus (MFG) was larger for different faces as compared to same faces, replicating previous observations of a recovery from facial identity adaptation in this region. However, there was no significant recovery from adaptation when different inverted faces were presented. Most interestingly, the difference in activation between upright and inverted faces increased progressively during a block when different facial identities were presented. A similar pattern of activation was found in the left middle fusiform gyrus, but was less clear-cut in bilateral face-sensitive areas of the inferior occipital cortex. These findings show that the differential level of activation to upright and inverted faces in the fusiform gyrus is mainly due to a difference in recovery from adaptation, and they explain the discrepancies in the results reported in previous fMRI studies which compared the processing of upright and inverted faces. The lack of recovery from adaptation for inverted faces in the fusiform gyrus may underlie the face inversion effect (FIE), which takes place during perceptual encoding of individual face representations.

Processus attentionnels, mémoire de travail visuospatiale et genèse des représentations numériques: une approche neuropsychologique

Report (2005)

Face-sensitive responses in the occipital inferior cortex of normal humans through feedback inputs from the fusiform gyrus ?: Evidence from neuroimaging studies of brain-damaged prosopagnosic patients

Poster (2004, June)

In humans, neuroimaging studies have identified two major visual extrastriate areas presenting face-sensitive responses: in the inferior occipital cortex (‘occipital face area’, OFA), and the middle fusiform gyrus (the ‘fusiform face area’, FFA), with a right hemispheric dominance. It has been proposed that the OFA, located anteriorly to foveal V4v (Halgren et al., 1999), has a critical role in the early perception of facial features and provides the feedforward outputs to later stages of face processing in both the FFA and the STS (Haxby et al., 2000). However, we have recently reported a normal activation of the right FFA despite a lesion encompassing the region of the right OFA in a brain-damaged prosopagnosic patient, PS (Rossion et al., 2003), suggesting that the face-sensitive responses observed at the level of the OFA in normals may rather arise from feedback connections from the FFA. Here we provide complementary fMRI evidence supporting this view. First, the normal differential activation for faces and objects in the right FFA of PS was observed only for left visual field presentations and is thus unlikely to originate from contralateral intact regions of the occipital cortex (e.g. left OFA). Second, the time-course in the right FFA and left OFA of PS for centrally presented items suggests an earlier differential activity between faces and objects in the most anterior region, the FFA. Finally, we imaged another (prosop)agnosic patient (NS, Delvenne et al., 2004) with a lesion encompassing the right FFA but sparing all posterior visual areas, and failed to disclose any face-sensitive response in his nonetheless structurally and functionnally intact occipital cortex. Together, these findings illustrate the necessary role of both the right FFA and OFA for accurate face perception, and reinforce the hypothesis that a dominant (feedback) connection from the FFA to the OFA subtends face-sensitive responses observed in the latter area when processing faces.

The functionally defined right occipital and fusiform "face areas" discriminate novel from visually familiar faces

in NeuroImage (2003), 19(3), 877-883

Neuroimaging (PET and fMRI) studies have identified a set of brain areas responding more to faces than to other object categories in the visual extrastriate cortex of humans. This network includes the middle lateral fusiform gyrus (the fusiform face area, or FFA) as well as the inferior occipital gyrus (occipital face area, OFA). The exact functions of these areas in face processing remain unclear although it has been argued that their primary function is to distinguish faces from nonface object categories-"face detection"-or also to discriminate among faces, irrespective of their visual familiarity to the observer. Here, we combined the data from two previous positron emission tomography (PET) studies to show that the functionally defined face areas are involved in the automatic discrimination between unfamiliar faces and familiar faces. Consistent with previous studies, a face localizer contrast (faces-objects) revealed bilateral activation in the middle lateral fusiform gyrus (FFA, BA37) and in the right inferior occipital cortex (OFA, BA19). Within all the regions of the right hemisphere, larger levels of activation were found for unfamiliar as compared to familiar faces. These results suggest that the very same areas involved in categorizing faces at the basic or individual level, play a role in differentiating familiar faces from new faces, showing an overlap between visual and presemantic mnesic representations of faces in the right hemisphere.

A pet study of human skill learning: Changes in brain activity related to learning an orientation discrimination task

in Cortex: A Journal Devoted to the Study of the Nervous System and Behavior (2001), 37(2), 243-265

Using 15O-water 3D positron emission tomography we investigated the effect of training in orientation discrimination upon cerebral activity in healthy human adults. When subjects are trained in this discrimination task, they learn the visuo-motor stimulus-response association required by the task and they increase their perceptual abilities in orientation discrimination. The present study was designed to investigate the rCBF modifications related to both these learning processes induced by training in orientation discrimination. PET data were acquired on two separate days (before and after training). Comparing the activation pattern related to orientation discrimination before and after the training period we observed activity decreases located in the left cerebellar cortex, in the right precentral gyrus and bilaterally in the fusiform gyri. The only region showing an activity increase was located in the body of the right caudate nucleus. These findings confirm the role of the neostriatum in skill learning and highlight the importance of mechanisms resulting in cortical and cerebellar neuronal activity decreases in this type of learning.

Effect of familiarity on the processing of human faces

in NeuroImage (1999), 9(3), 278289

Most brain imaging studies on face perception have investigated the processing of unknown faces and addressed mainly the question of specific face processing in the human brain. The goal of this study was to highlight the effects of familiarity on the visual processing of faces. Using [15O]water 3D Positron Emission Tomography, regional cerebral blood flow distribution was measured in 11 human subjects performing an identical task (gender categorization) on both unknown and known faces. Subjects also performed two control tasks (a face recognition task and a visual pattern discrimination task). They were scanned after a training phase using videotapes during which they had been familiarized with and learned to recognize a set of faces. Two major results were obtained. On the one hand, we found bilateral activations of the fusiform gyri in the three face conditions, including the so-called fusiform-face area, a region in the right fusiform gyrus specifically devoted to face processing. This common activation suggests that different cognitive tasks performed on known and unknown faces require the involvement of this fusiform region. On the other hand, specific regional cerebral blood flow changes were related to the processing of known and unknown faces. The left amygdala, a structure involved in implicit learning of visual representations, was activated by the categorization task on unknown faces. The same task on known faces induced a relative decrease of activity in early visual areas. These differences between the two categorization tasks reveal that the human brain processes known and unknown faces differently.

PET study of human voluntary saccadic eye movements in darkness: Effect of task repetition on the activation pattern

in European Journal of Neuroscience (1998), 10

Using H2(15)O 3D Positron Emission Tomography (PET), regional cerebral blood flow (rCBF) was measured in six human subjects under two different conditions: at rest and while performing self-paced horizontal saccadic eye movements in darkness. These two conditions were repeated four times each. First, the comparison between the four saccadic and four resting conditions was investigated in a group and a single subject analysis. Saccades elicited bilateral rCBF increases in the medial part of the superior frontal gyrus (supplementary eye field), precentral gyrus (frontal eye field), superior parietal lobule, anterior medial part of the occipital lobe involving striate and extrastriate cortex (lingual gyrus and cuneus), and in the right inferior parietal lobule. At the subcortical level, activations were found in the left putamen. These results mainly replicate previous PET findings on saccadic control. Second, the interaction between the experimental conditions and their repetition was examined. When activations throughout repetition of the same saccadic task are compared, the supplementary eye fields show a progressive increase of activation. On the contrary, the activation in the cerebellum, left superior parietal lobule and left occipital cortex progressively decreases during the scanning session. Given the existence of such an interaction, the pattern of activations must be interpreted as a function of task repetition. This may be a factor explaining some apparent mismatch between different studies.

Specific activation related to proper name retrieval associated with faces

Poster (1997, October)

Orientation-specific training effect in visual orientation discrimination, a pet study

Poster (1996)