Holistic perception of individual faces in the right middle fusiform gyrus as evidenced by the composite face illusion

in Journal of Vision (2010), 10(2), 1-16

The perception of a facial feature (e.g., the eyes) is influenced by the position and identity of other features (e.g., the mouth) supporting an integrated, or holistic, representation of individual faces ... [more ▼]

The perception of a facial feature (e.g., the eyes) is influenced by the position and identity of other features (e.g., the mouth) supporting an integrated, or holistic, representation of individual faces in the human brain. Here we used an event-related adaptation paradigm in functional magnetic resonance imaging (fMRI) to clarify the regions representing faces holistically across the whole brain. In each trial, observers performed the same/different task on top halves (aligned or misaligned) of two faces presented sequentially. For each face pair, the identity of top and bottom parts could be both identical, both different, or different only for the bottom half. The latter manipulation resulted in a composite face illusion, i.e., the erroneous perception of identical top parts as being different, only for aligned faces. Release from adaptation in this condition was found in two sub-areas of the right middle fusiform gyrus responding preferentially to faces, including the “fusiform face area” (“FFA”). There were no significant effects in homologous regions of the left hemisphere or in the inferior occipital cortex. Altogether, these observations indicate that face-sensitive populations of neurons in the right middle fusiform gyrus are optimally tuned to represent individual exemplars of faces holistically. [less ▲]

Is the cerebral processing of categorical and coordinate spatial relations based on different or identical but differentially activated functional networks?

Scientific Conference (2009, September)

The fundamental hypothesis related to the distinction between categorical and coordinate processing has been that these two types of spatial relations coding are qualitatively different. Based on ... [more ▼]

The fundamental hypothesis related to the distinction between categorical and coordinate processing has been that these two types of spatial relations coding are qualitatively different. Based on Kosslyn’s initial hemispheric specialization theory, they also are hypothesized to rely on different functional networks in the brain which are supposed to have evolved in a way to take advantage of more fundamental hemispheric specializations in order to adapt these hemispheric strengths to the processing of the two different types of spatial relations. (...) [less ▲]

Face inversion disrupts the perception of vertical relations between features in the right human occipito-temporal cortex

in Journal of Neuropsychology (2009), 3

The impact of inversion on the extraction of relational and featural face information was investigated in two fMRI experiments. Unlike previous studies, the contribution of horizontal and vertical spatial ... [more ▼]

The impact of inversion on the extraction of relational and featural face information was investigated in two fMRI experiments. Unlike previous studies, the contribution of horizontal and vertical spatial relations were considered separately since they have been shown to be differentially vulnerable to face inversion (Goffaux & Rossion, 2007). Hence, inversion largely affects the perception of vertical relations (e.g. eye or mouth height) while the processing of features (e.g. eye shape and surface) and of horizontal relations (e.g. inter-ocular distance) is affected to a far lesser extent. Participants viewed pairs of faces that differed either at the level of one local feature (i.e. the eyes) or of the spatial relations of this feature with adjacent features. Changes of spatial relations were divided into two conditions, depending on the vertical or horizontal axis of the modifications. These stimulus conditions were presented in separate blocks in the first (block) experiment while they were presented in a random order in the second event-related (ER) experiment. Face-preferring voxels located in the right-lateralized middle fusiform gyrus (rMFG) largely decreased their activity with inversion. Inversion-related decreases were more moderate in left-lateralized middle fusiform gyrus (lMFG). ER experiment revealed that inversion affected rMFG and lMFG activity in distinct stimulus conditions. Whereas inversion affected lMFG processing only in featural condition, inversion selectively affected the processing of vertical relations in rMFG. Correlation analyses further indicated that the inversion effect (IE) observed in rMFG and right inferior occipital gyrus (rIOG) reliably predicted the large behavioural IE observed for the processing of vertical relations. In contrast, lMFG IE correlated with the weak behavioural IE observed for the processing of horizontal relations. Our findings suggest that face configuration is mostly encoded in rMFG, whereas more local aspects of face information, such as features and horizontal spatial relations drive lMFG processing. These findings corroborate the view that the vulnerability of face perception to inversion stems mainly from the disrupted processing of vertical face relations in the right-lateralized network of face-preferring regions (rMFG, rIOG). [less ▲]

Gender and mathematical competencies!?

Scientific Conference (2008, September 04)

Gender and mathematical competencies!?

Scientific Conference (2008)

Evidence for individual face discrimination in non-face selective areas of the visual cortex in acquired prosopagnosia

in Behavioral Neurology (2008), 19(1-2), 75-79

Two areas in the human occipito-temporal cortex respond preferentially to faces: 'the fusiform face area' ('FFA') and the 'occipital face area' ('OFA'). However, it is unclear whether these areas have an ... [more ▼]

Two areas in the human occipito-temporal cortex respond preferentially to faces: 'the fusiform face area' ('FFA') and the 'occipital face area' ('OFA'). However, it is unclear whether these areas have an exclusive role in processing faces, or if sub-maximal responses in other visual areas such as the lateral occipital complex (LOC) are also involved. To clarify this issue, we tested a brain-damaged patient (PS) presenting a face-selective impairment with functional magnetic resonance imaging (fMRI). The right hemisphere lesion of the prosopagnosic patient encompasses the 'OFA' but preserves the 'FFA' and LOC. Using fMRI-adaptation, we found a larger response to different faces than repeated faces in the ventral part of the LOC both for normals and the patient, next to her right hemisphere lesion. This observation indicates that 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 perception of individual faces. [less ▲]

Investigation of featural versus configural processing of faces in the middle fusiform gyrus

Poster (2007, May)

Inverting a face affects the processing of the vertical relations between features (e.g. eye height) more than the processing of horizontal relations (e.g. interocular distance) and of local features (e.g ... [more ▼]

Inverting a face affects the processing of the vertical relations between features (e.g. eye height) more than the processing of horizontal relations (e.g. interocular distance) and of local features (e.g. eye shape and surface). Inversion also decreases hemodynamic responses (HR) in face-sensitive regions in the middle fusiform gyrus (MFG), presumably because it reduces face distinctiveness and leads to larger adaptation. Here we tested the hypothesis that inversion affects the perception of vertical metric distances between features in the MFG. In the present fMRI study, twelve subjects were presented with short blocks of upright and inverted pairs composed either of identical faces (‘same’ condition), or of faces that differed at the level of ‘vertical’ relations, ‘horizontal’ relations, the shape of all inner feature (‘different’), or the shape of one single ‘feature’. In rMFG, smaller HR were observed for ‘same’ as compared to ‘different’ condition when faces were presented upright; due to HR adaptation. ‘Vertical’, ‘horizontal’ and ‘featural’ conditions led to HR close to ‘same’ condition. Inversion decreased HR in all conditions except the ‘same’ condition, thus replicating previous findings. The largest inversion-related decrements measured in rMFG were observed for vertical relations. In the left MFG, all conditions led to larger HR than the ‘same’ condition at upright. Inversion decreased HR in vertical and horizontal conditions only. These results suggest different roles of the MFG across hemispheres. rMFG may code ecological face differences, since release from adaptation was only observed for completely different faces in this region. Moreover, rMFG may be sensitive to face configuration as suggested by the generalised inversion-related HR decrease. In contrast, lMFG may code any kind of physical difference between faces irrespective of orientation, except for relational differences. [less ▲]

Understanding the functional neuroanatomy of acquired prosopagnosia

in NeuroImage (2007), 35(2), 836-852

One of the most remarkable disorders following brain damage is prosopagnosia, the inability to recognize faces. While a number of cases of prosopagnosia have been described at the behavioral level, the ... [more ▼]

One of the most remarkable disorders following brain damage is prosopagnosia, the inability to recognize faces. While a number of cases of prosopagnosia have been described at the behavioral level, the functional neuroanatomy of this face recognition impairment, and thus the brain regions critically involved in normal face recognition, has never been specified in great detail. Here, we used anatomical and functional magnetic resonance imaging (fMRI) to present the detailed functional neuroanatomy of a single case of acquired prosopagnosia (PS; Rossion, B., Caldara, R., Seghier, M., Schuller, A.-M., Lazeyras, F., Mayer, E., 2003a. A network of occipito-temporal face-sensitive areas besides the right middle fusiform gyrus is necessary for normal face processing. Brain 126, 2381-95; Rossion, B., Joyce, C.A., Cottrell, G.W., Tarr, M.J., 2003b. Early lateralization and orientation tuning for face, word, and object processing in the visual cortex. Neuroimage 20, 1609-24) with normal object recognition. First, we clarify the exact anatomical location and extent of PS' lesions in relation to (a) retinotopic cortex, (b) face-preferring regions, and (c) other classical visual regions. PS' main lesion - most likely causing her prosopagnosia - is localized in the posterior part of the right ventral occipitotemporal cortex. This lesion causes a left superior paracentral scotoma, as frequently observed in cases of prosopagnosia. While the borders of the early visual areas in the left hemisphere could be delineated well, the extensive posterior right-sided lesion hampered a full specification of the cortical representation of the left visual field. Using multiple scanning runs, face-preferring activation was detected within the right middle fusiform gyrus (MFG) in the so-called 'fusiform face area' ('FFA'), but also in the left inferior occipital gyrus (left 'OFA'), and in the right posterior superior temporal sulcus (STS). The dorsal part of the lateral occipital complex (LOC) and the human middle temporal cortex (hMT+/V5) were localized bilaterally. The color-preferring region V4/V8 was localized only in the left hemisphere. In the right hemisphere, the posterior lesion spared the ventral part of LOC, a region that may be critical for the preserved object recognition abilities of the patient, and the restriction of her deficit to the category of faces. The presumptive functions of both structurally damaged and preserved regions are discussed and new hypotheses regarding the impaired and preserved abilities of the patient during face and non-face object processing are derived. Fine-grained neurofunctional analyses of brain-damaged single cases with isolated recognition deficits may considerably improve our knowledge of the brain regions critically involved in specific visual functions, such as face recognition. [less ▲]

Computer assisted assessment of visuospatial working memory

Poster (2007)

We present a new computer program that allows the assessment of visuospatial working memory (VSWM) in kindergarten children. The challenge for the assessment of VSWM in this age group is to present a test ... [more ▼]

We present a new computer program that allows the assessment of visuospatial working memory (VSWM) in kindergarten children. The challenge for the assessment of VSWM in this age group is to present a test design that is easily understandable for children and thus not too difficult while at the same time implying additional processing elements above the pure storage of positional information (according to the definition of Engle et al. 1999 that working memory combines an element of pure storage with processes of executive attention) The adopted test paradigm is based on a grid / no-grid paradigm for which a previous fMRI study with an adult population has shown that the memorization of positional information in a perceptively undifferentiated space (no-grid condition) requires additional attentional processes compared to the memorization of positional information in a perceptively structured space (grid condition). The setting of the test was adapted to children in Kindergarten. We used a tablet PC to administer the test. This procedure excludes that children fail because they can’t use the computer mouse in an appropriate way. The different items show a 4x4 grid where the eyes of a manikin appear on a dark background. Children are told that the positions of different manikins in a dark room have to be memorized. After a short period of time the eyes disappear again and up to four positions have to be memorized in this way. The test person then clicks in the grid where he believes that the different manikins are hidden. The setting allows measuring performance in terms of accuracy and time. First results with kindergarten children in Luxemburg will be presented showing the correlation of this VSWM task with other visuospatial and numerical tasks. [less ▲]

Faces are represented holistically in the human occipito-temporal cortex

in NeuroImage (2006), 32(3), 1385-1394

Two identical top parts of a face photograph look different if their bottom parts differ. This perceptual illusion, the "face composite effect", is taken as strong evidence that faces are processed as a ... [more ▼]

Two identical top parts of a face photograph look different if their bottom parts differ. This perceptual illusion, the "face composite effect", is taken as strong evidence that faces are processed as a whole rather than as a collection of independent features. To test the hypothesis that areas responding preferentially to faces in the human brain represent faces holistically, we recorded functional magnetic resonance imaging (fMRI) during an adaptation paradigm with the composite face illusion. In both the middle fusiform gyrus (MFG) and the inferior occipital gyrus (IOG), we observed a significantly larger response to the same top face when it was aligned with different bottom parts than with the same bottom part, with a most robust effect in the right middle fusiform gyrus. This difference was not found when the top and the bottom face parts were spatially misaligned or when the faces were presented upside-down. These findings indicate that facial features are integrated into holistic face representations in areas of the human visual cortex responding preferentially to faces. [less ▲]