Dissociated face- and word-selective intracerebral responses in the human ventral occipito-temporal cortex

in Journal of Vision (2020, October), 20(11),

The extent to which faces and written words share neural circuitry in the human brain is actively debated. We provide an original contribution to this debate by comparing face-selective and word-selective ... [more ▼]

The extent to which faces and written words share neural circuitry in the human brain is actively debated. We provide an original contribution to this debate by comparing face-selective and word-selective responses in a large group of patients (N=37) implanted with intracerebral electrodes in the ventral occipito-temporal cortex (VOTC). Both face-selective (i.e., significantly different responses to faces vs. nonface objects) and word-selective (i.e., significantly different responses to words vs. pseudofonts) neural activity is isolated through frequency-tagging (Jonas et al., 2016; Lochy et al., 2018, respectively). Critically, this approach allows disentangling category-selective neural responses from general visual responses. Overall, we find that 69.26% of significant contacts show either face- or word-selectivity, with the expected right and left hemispheric dominance, respectively (Fig.1A,B). Moreover, the center of mass for word-contacts is more lateral than for face-contacts, with no differences in postero-anterior axis (Fig.2A). Spatial dissociations are also found within core regions of face and word processing, with a medio-lateral dissociation in the fusiform gyrus (FG) and surrounding sulci (FG+sulci;Fig.2B), while a postero-anterior dissociation is found in the inferior occipital gyrus (IOG;Fig.2C). Despite their spatial dissociations in the FG+sulci and IOG, most overlap in category-selective responses is found in these regions (Fig.1C). Critically, in the overlap-contacts, across the whole brain or specifically in the FG+sulci, between-category (word-face) selective-amplitudes showed no-to-weak correlations, despite strong correlations for within-category (face-face, word-word) selective-amplitudes (Fig.3A), and a strong correlation in non-selective general-amplitudes to words-faces. Moreover, substantial overlap and no-to-weak correlations were observed between faces and a control category (houses) known to be functionally dissociated from faces. Overall, we conclude that category-selectivity for faces and words is largely dissociated in the human VOTC, with a limited spatial overlap likely due to the distant recording of dissociated populations of neurons rather than to shared category-selective representations. [less ▲]

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 ... [more ▼]

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. [less ▲]

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 ... [more ▼]

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. [less ▲]

Attentional shifts due to irrelevant numerical cues: Behavioral investigation of a lateralized target discrimination paradigm

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

Behavioural evidence indicates the existence of a link between numerical representations and visuo-spatial processes. A striking demonstration of this link was provided by Fischer and colleagues (2003 ... [more ▼]

Behavioural evidence indicates the existence of a link between numerical representations and visuo-spatial processes. A striking demonstration of this link was provided by Fischer and colleagues (2003), who reported that participants detect a target more rapidly in the left hemifield, if it is preceded by a small number (e.g. 2 or 3) and more rapidly 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 different visual hemifields (e.g., left and right) depending on their magnitude (e.g., small and large, respectively). Here, we sought to replicate number-related attentional shifts using a discrimination task. The participants (n=16) were presented 1 digit (1,2 vs. 8,9) at the centre of the screen for 400ms. After 500ms, 1000ms or 2000ms, a target was briefly flashed in either the right or left hemifield and participants had to report its colour (red or green). They were told that the central digit was irrelevant to the task. We hypothesized that the attentional shift induced by the centrally presented numbers should induce congruency effects for the target discrimination task, so that small (or large) numbers would facilitate the processing of left (or right) targets. Our results confirmed this prediction, but only for the shortest digit-target interval (500ms). This is supported by a significant interaction between number magnitude (small/large) and target hemifield (left/right). The link between numerical and spatial representations further predicts a positive relation between number magnitude and the difference in RT between left and right targets. Regression slopes were computed individually and a positive slope was obtained for short number-target interval. These findings indicate that the attentional shifts induced by irrelevant numerical material are independent of the exact nature of target processing (discrimination vs. detection). [less ▲]

Temporal order judgment and simple reaction times: evidence for a common processing system.

in Journal of vision (2007), 7(6), 11

We present a simple reaction time (RT) versus temporal order judgment (TOJ) experiment as a test of the perception-action relationship. The experiment improves on previous ones in that it assesses for the ... [more ▼]

We present a simple reaction time (RT) versus temporal order judgment (TOJ) experiment as a test of the perception-action relationship. The experiment improves on previous ones in that it assesses for the first time RT and TOJ on a trial-by-trial basis, hence allowing the study of the two behaviors within the same task context and, most importantly, the association of RT to "correct" and "incorrect" TOJs. RTs to pairs of stimuli are significantly different depending on the associated TOJs, an indication that perceptual and motor decisions are based on the same internal response. Simulations with the simplest one-system model (J. Gibbon & R. Rutschmann, 1969) using the means and standard deviations of the RT to stimuli presented in isolation yield excellent fits of the mean RT to these increments when presented in sequence and moderately good fits of the RT when classified according to the TOJ categories. The present observation that the point of subjective simultaneity for stimulus pairs is systematically smaller than the difference in RT to each of the two increments in the same pairs pleads, however, in favor of distinct decision criteria for perception and action with the former below the latter. For such a case, standard one-system race models require that the internal noise associated with the TOJ be less than the one associated with the RT to the same stimulus pair. The present data show the reverse state of affairs. In short, data and simulations comply with "one-system-two-decision" models of perceptual and motor behaviors, while prompting further testing and modeling to account for the apparent discrepancy between the ordering of the two decisions. [less ▲]