Phase-scrambled Faces Research Articles

Pupillary Responses to Dot Patterns on a Human Face Background.

Dots on natural backgrounds can elicit significant pupillary constrictions within the entire image phase associated with parasympathetic activation, suggesting disgust rather than fear. Although studies have reported that dots on faces elicit stronger disgust than dots on non-face backgrounds, it remains unclear whether dots on a face elicit stronger pupil constrictions than non-face backgrounds. Pupillometry was used while viewing dots on faces and compared with luminance- and spatial frequency-controlled images (dots on phase-scrambled faces) and luminance-controlled images (face only, phase-scrambled faces). Relative pupillary constrictions were elicited when dots were placed on faces and phase-scrambled faces; however, the response to dots on faces did not differ significantly from that to the control stimuli. Approximately 3-5 s after stimulus onset, pupillary responses to dots on faces recovered to baseline faster than those to dots on phase-scrambled faces with a larger pupil size. The initial pupillary constrictions observed are consistent with those in response to dots on natural backgrounds, suggesting that regardless of the background, dots may stimulate parasympathetic activation and elicit disgust rather than fear. The faster recovery from the pupil constriction and larger pupil size in the later phase may be caused by a dynamic balance between the sympathetic and parasympathetic neuronal activities.

Time-resolved classification of dog brain signals reveals early processing of faces, species and emotion

Dogs process faces and emotional expressions much like humans, but the time windows important for face processing in dogs are largely unknown. By combining our non-invasive electroencephalography (EEG) protocol on dogs with machine-learning algorithms, we show category-specific dog brain responses to pictures of human and dog facial expressions, objects, and phase-scrambled faces. We trained a support vector machine classifier with spatiotemporal EEG data to discriminate between responses to pairs of images. The classification accuracy was highest for humans or dogs vs. scrambled images, with most informative time intervals of 100–140 ms and 240–280 ms. We also detected a response sensitive to threatening dog faces at 30–40 ms; generally, responses differentiating emotional expressions were found at 130–170 ms, and differentiation of faces from objects occurred at 120–130 ms. The cortical sources underlying the highest-amplitude EEG signals were localized to the dog visual cortex.

Spontaneously emerging patterns in human visual cortex and their functional connectivity are linked to the patterns evoked by visual stimuli.

The function of spontaneous brain activity is an important issue in neuroscience. Here we test the hypothesis that patterns of spontaneous activity code representational patterns evoked by stimuli. We compared in human visual cortex multivertex patterns of spontaneous activity to patterns evoked by ecological visual stimuli (faces, bodies, scenes) and low-level visual features (e.g., phase-scrambled faces). Specifically, we identified regions that preferred particular stimulus categories during localizer scans (e.g., extrastriate body area for bodies), measured multivertex patterns for each category during event-related task scans, and then correlated over vertices these stimulus-evoked patterns to the pattern measured on each frame of resting-state scans. The mean correlation coefficient was essentially zero for all regions/stimulus categories, indicating that resting multivertex patterns were not biased toward particular stimulus-evoked patterns. However, the spread of correlation coefficients between stimulus-evoked and resting patterns, positive and negative, was significantly greater for the preferred stimulus category of an ROI. The relationship between spontaneous and stimulus-evoked multivertex patterns also governed the temporal correlation or functional connectivity of patterns of spontaneous activity between individual regions (pattern-based functional connectivity). Resting multivertex patterns related to an object category fluctuated preferentially between ROIs preferring the same category, and fluctuations of the pattern for a category (e.g., body) within its preferred ROIs were largely uncorrelated with fluctuations of the pattern for a disparate category (e.g., scene) within its preferred ROIs. These results support the proposal that spontaneous multivertex activity patterns are linked to stimulus-evoked patterns, consistent with a representational function for spontaneous activity.NEW & NOTEWORTHY Spontaneous brain activity was once thought to reflect only noise, but evidence of strong spatiotemporal regularities has motivated a search for functional explanations. Here we show that the spatial pattern of spontaneous activity in human high-level and early visual cortex is related to the spatial patterns evoked by stimuli. Moreover, these patterns partly govern spontaneous spatiotemporal interactions between regions, so-called functional connectivity. These results support the hypothesis that spontaneous activity serves a representational function.

Maternal Depressive Symptoms During the Pre‐ and Postnatal Periods and Infant Attention to Emotional Faces

We examined how infants' attentional disengagement from happy, fearful, neutral, and phase-scrambled faces at 8months, as assessed by eye tracking, is associated with trajectories of maternal depressive symptoms from early pregnancy to 6months postpartum (decreasing n=48, increasing n=34, and consistently low symptom levels n=280). The sample (mother-infant dyads belonging to a larger FinnBrain Birth Cohort Study) was collected between 5/2013-6/2016. The overall disengagement probability from faces to distractors was not related to maternal depressive symptoms, but fear bias was heightened in infants whose mothers reported decreasing or increasing depressive symptoms. Exacerbated attention to fearful faces in infants of mothers with depressive symptoms may be independent of the timing of the symptoms in the pre- and postnatal stages.

Maternal pre- and postnatal anxiety symptoms and infant attention disengagement from emotional faces

BackgroundBiases in socio-emotional attention may be early markers of risk for self-regulation difficulties and mental illness. We examined the associations between maternal pre- and postnatal anxiety symptoms and infant attention patterns to faces, with particular focus on attentional biases to threat, across male and female infants. MethodsA general population, Caucasian sample of eight-month old infants (N = 362) were tested using eye-tracking and an attention disengagement (overlap) paradigm, with happy, fearful, neutral, and phase-scrambled faces and distractors. Maternal self-reported anxiety symptoms were assessed with the Symptom Checklist-90/anxiety subscale at five time points between gestational week 14 and 6 months postpartum. ResultsProbability of disengagement was lowest for fearful faces in the whole sample. Maternal pre- but not postnatal anxiety symptoms associated with higher threat bias in infants, and the relation between maternal anxiety symptoms in early pregnancy and higher threat bias in infants remained significant after controlling for maternal postnatal symptoms. Maternal postnatal anxiety symptoms, in turn, associated with higher overall probability of disengagement from faces to distractors, but the effects varied by child sex. LimitationsThe small number of mothers suffering from very severe symptoms. No control for the comorbidity of depressive symptoms. ConclusionsMaternal prenatal anxiety symptoms associate with infant's heightened attention bias for threat. Maternal postnatal anxiety symptoms, in turn, associate with infant's overall disengagement probability differently for boys and girls. Boys may show enhanced vigilance for distractors, except when viewing fearful faces, and girls enhanced vigilance for all socio-emotional stimuli. Long-term implications of these findings remain to be explored.

Face-Inversion Effect on Disgust Evoked by a Cluster of Dots.

A cluster of dots such as lotus seed pods evokes extremely strong disgust when it is placed on human and animal skins. However, few empirical studies have examined the role of the background image, such as skin, in the generation of disgust. In this study, we investigated whether the orientation of background faces influences the disgust evoked by the dot pattern. The participants were asked to evaluate disgust to an upright, inverted, or phase-scrambled face image with or without a cluster of dots on it and then complete a questionnaire measuring trypophobia proneness (Trypophobia Questionnaire). The results suggested that disgust was intensified by the background faces, especially by the upright faces. The intensification of disgust in the upright face was correlated positively with the Trypophobia Questionnaire scores. The results indicated a face-inversion effect on the disgust to the dot pattern, suggesting a significant role of the background image.

The impact of orientation filtering on face-selective neurons in monkey inferior temporal cortex.

Faces convey complex social signals to primates. These signals are tolerant of some image transformations (e.g. changes in size) but not others (e.g. picture-plane rotation). By filtering face stimuli for orientation content, studies of human behavior and brain responses have shown that face processing is tuned to selective orientation ranges. In the present study, for the first time, we recorded the responses of face-selective neurons in monkey inferior temporal (IT) cortex to intact and scrambled faces that were filtered to selectively preserve horizontal or vertical information. Guided by functional maps, we recorded neurons in the lateral middle patch (ML), the lateral anterior patch (AL), and an additional region located outside of the functionally defined face-patches (CONTROL). We found that neurons in ML preferred horizontal-passed faces over their vertical-passed counterparts. Neurons in AL, however, had a preference for vertical-passed faces, while neurons in CONTROL had no systematic preference. Importantly, orientation filtering did not modulate the firing rate of neurons to phase-scrambled face stimuli in any recording region. Together these results suggest that face-selective neurons found in the face-selective patches are differentially tuned to orientation content, with horizontal tuning in area ML and vertical tuning in area AL.

Relative sensitivity to low- vs. high-level visual properties in face-sensitive regions of the human ventral occipito-temporal cortex: evidence from intra-cerebral recordings

Neuroimaging studies have identified a network of regions in the human ventral occipito-temporal cortex (VOTC) sensitive to faces. Using intra-cerebral electrophysiological recordings, we compared the relative responsivity of the different regions to face-structure using a periodic visual stimulation paradigm. Recordings were made in 17 epileptic patients implanted with linear-array depth-electrodes (>1000 contacts in the VOTC). In Experiment 1, we presented sequences of phase-scrambled and intact face stimuli (equalised for low-level image properties) alternating at a fixed frequency of 3Hz (6 images/s) while patients completed an orthogonal task. Significant periodic EEG responses (SSVEPs) reflecting high-level face structure processing were found at 3 Hz, while responses reflecting low-level visual processing (e.g. local contrast change) were recorded at 6 Hz. An index of high-level processing (3Hz/(3Hz+6Hz)) showed a posterior-to-anterior gradient, reflecting increased sensitivity to face structure going from the occipital to the temporo-polar cortex, with a right hemisphere lateralisation. In Experiment 2, we further investigated face structure processing with a sweep VEP paradigm (Ales et al., 2012; 4/17 patients). Stimulation was similar to Experiment 1 except the visibility (phase coherence) of the face image was parametrically varied so that a face gradually emerged over the course of a sequence. The patients performed a face detection task during the trials. Responses at 3Hz, objective markers of face detection, were found in all patients on contacts in the lateral fusiform gyrus and inferior occipital gyrus that overlapped with those defined in Experiment 1. All regions showed non-linear voltage vs coherence functions at 3Hz, with thresholds lying around ≈40% coherence. Sites in the lateral fusiform gyrus had a distinct step-like response profile suggestive of categorical face detection. These findings demonstrate that face-sensitive regions are organised with a posterior-to-anterior gradient of increasingly selective high-level visual processing. These regions appear to detect face structure in a non-linear/categorical manner. Meeting abstract presented at VSS 2015.

The effect of contrast polarity reversal on face detection: Evidence of perceptual asymmetry from sweep VEP

Contrast polarity inversion (i.e., turning dark regions light and vice versa) impairs face perception. We investigated the perceptual asymmetry between positive and negative polarity faces (matched for overall luminance) using a sweep VEP approach in the context of face detection (Journal of Vision 12 (2012) 1–18). Phase-scrambled face stimuli alternated at a rate of 3Hz (6images/s). The phase coherence of every other stimulus was parametrically increased so that a face gradually emerged over a 20-s stimulation sequence, leading to a 3Hz response reflecting face detection. Contrary to the 6Hz response, reflecting low-level visual processing, this 3Hz response was larger and emerged earlier over right occipito-temporal channels for positive than negative polarity faces. Moreover, the 3Hz response emerged abruptly to positive polarity faces, whereas it increased linearly for negative polarity faces. In another condition, alternating between a positive and a negative polarity face also elicited a strong 3Hz response, indicating an asymmetrical representation of positive and negative polarity faces even at supra-threshold levels (i.e., when both stimuli were perceived as faces). Overall, these findings demonstrate distinct perceptual representations of positive and negative polarity faces, independently of low-level cues, and suggest qualitatively different detection processes (template-based matching for positive polarity faces vs. linear accumulation of evidence for negative polarity faces).

Investigating the role of the internal features of the face in competition for representation by modulation of the face-sensitive N170

Event Abstract Back to Event Investigating the role of the internal features of the face in competition for representation by modulation of the face-sensitive N170 Sreekari Vogeti1* and Paul M. Corballis1 1 University of Auckland, School of Psychology, New Zealand When two or more faces are presented at the same time, they appear to 'compete' for representation in the visual system (R. Desimone & J. Duncan, Ann. Rev. Neurosci., 1995). Evidence for this idea comes from several studies investigating the modulation of the face-sensitive N170 component of the event-related brain potential (ERP) by competition between faces (e.g., C. Jacques & B. Rossion, J. Vis., 2006). The N170 evoked by the presentation of a face image is attenuated in amplitude when the face is flanked by other face images compared to when it is flanked by other objects or by phase-scrambled faces. Some studies have suggested that the internal features of the face - in particular the eye region - may be especially important in the face-sensitivity of the N170 (Itier, Alain, Sedore and McIntosh (2007); however a majority of studies have failed to report modulations of the N170 that support this idea. In the present study we employed the competitive modulation of N170 amplitude as a paradigm to explore the role that the features of the face play in competition for representation. We presented face stimuli drawn from three categories of internal face stimuli: features intact (FI), no eye region (NER), or no internal features (NIF). These stimuli were presented flanked either by stimuli from the same category, a different category or phase-scrambled control images. The N170 showed greater attenuation when intact internal faces were presented in the context of faces that appear more face-like (i.e. with FI and NER flankers) than with faces without any face-like features (NIF flankers). These data are suggestive that the eye regions do not play a dominant role in the face-sensitivity of the N170. Keywords: EEG, Event-related potentials, face recognition, N170, perceptual categorization Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Cognition and Executive Processes Citation: Vogeti S and Corballis PM (2015). Investigating the role of the internal features of the face in competition for representation by modulation of the face-sensitive N170. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00386 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Miss. Sreekari Vogeti, University of Auckland, School of Psychology, Auckland, New Zealand, svogeti@hotmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Sreekari Vogeti Paul M Corballis Google Sreekari Vogeti Paul M Corballis Google Scholar Sreekari Vogeti Paul M Corballis PubMed Sreekari Vogeti Paul M Corballis Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Developmental precursors of social brain networks: the emergence of attentional and cortical sensitivity to facial expressions in 5 to 7 months old infants.

Biases in attention towards facial cues during infancy may have an important role in the development of social brain networks. The current study used a longitudinal design to examine the stability of infants' attentional biases towards facial expressions and to elucidate how these biases relate to emerging cortical sensitivity to facial expressions. Event-related potential (ERP) and attention disengagement data were acquired in response to the presentation of fearful, happy, neutral, and phase-scrambled face stimuli from the same infants at 5 and 7 months of age. The tendency to disengage from faces was highly consistent across both ages. However, the modulation of this behavior by fearful facial expressions was uncorrelated between 5 and 7 months. In the ERP data, fear-sensitive activity was observed over posterior scalp regions, starting at the latency of the N290 wave. The scalp distribution of this sensitivity to fear in ERPs was dissociable from the topography of face-sensitive modulation within the same latency range. While attentional bias scores were independent of co-registered ERPs, attention bias towards fearful faces at 5 months of age predicted the fear-sensitivity in ERPs at 7 months of age. The current results suggest that the attention bias towards fear could be involved in the developmental tuning of cortical networks for social signals of emotion.

Electrophysiological correlates of visual adaptation and sensory competition

The face-sensitive evoked N170 component of the event related potential (ERP) is reduced if another face is presented before when compared to the previous presentation of a low-level control stimulus (phase-scrambled face). This effect is thought to reflect category-specific adaptation processes. Similarly, presenting two faces concurrently also reduces the N170, suggesting that stimuli compete for neural representations in the occipito-temporal cortex as early as 170ms. Here we compared the ERPs obtained for two faces or for a face and a phase-scrambled face in three different conditions: (1) a first stimulus (S1) followed by a second one (S2), similarly to previous adaptation paradigms; (2) S1 remaining on screen when S2 appeared, as previously used in studies of competition; (3) or S1 and S2 having simultaneous onset and offset as well. We found a significant and stimulus specific reduction of the N170 in both conditions where the onset of S1 preceded the onset of S2. In contrast, simultaneous presentation of the two stimuli had no specific effect on the ERPs at least until 200ms post-stimulus onset. This suggests either that competition does not lead to early repetition suppression or that the absence of a larger N170 response to two simultaneously presented face stimuli compared to a single stimulus reflects competition between overlapping representations. Overall, our results show that the asynchronous presentation of S1 and S2 is critical to observe stimulus specific reduction of the N170, presumably reflecting adaptation-related processes.

Modulation of the face-sensitive N170 by competition between faces and their features

Event Abstract Back to Event Modulation of the face-sensitive N170 by competition between faces and their features Sreekari Vogeti1* and Paul M. Corballis1* 1 The University of Auckland, New Zealand i. Background: When two or more faces are presented at the same time, they appear to ‘compete’ for representation in the visual system (R. Desimone & J. Duncan, Ann. Rev. Neurosci., 1995). Evidence for this idea comes from several studies investigating the modulation of the face-sensitive N170 component of the event-related brain potential (ERP) by competition between faces (e.g., C. Jacques & B. Rossion, J. Vis., 2006). The N170 evoked by the presentation of a face image is attenuated in amplitude when the face is flanked by other face images compared to when it is flanked by other objects or by phase-scrambled faces. Here, we explore the role that the features of the face play in competition for representation. Some studies have suggested that the internal features of the face – in particular the eye region – may be especially important in the face-sensitivity of the N170; however a majority of studies have failed to report modulations of the N170 that support this idea. ii. Methods: We employed the competitive modulation of N170 amplitude as a paradigm to explore what drives the N170 face effect. We presented face stimuli drawn from three categories of face stimuli: features intact (FI), no eye region (NER), or no internal features (NIF). These stimuli were presented flanked either by stimuli from the same category, a different category or phase-scrambled control images. iii. Results: In all conditions target faces showed greater N170 attenuation when presented in the context of ‘same category’ versus ‘different category’ flankers. Target faces competed more with ‘different category’ flankers that were more similar to the target face (i.e. FI targets competed more with NER than with NIF flankers; NIF targets competed more with NER than with FI flankers). Furthermore, N170 amplitude was more attenuated for targets that were less ‘face like’ (i.e. NIF had the lowest N170 amplitude and FI had the greatest amplitude). iv. Discussion: This graded modulation of N170 suggests that the ‘face effect’ may be driven more by holistic face processing rather than exclusively by the eye region. Keywords: N170, Face-processing, event-related potentials (ERPs), faces, features Conference: ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013. Presentation Type: Poster Topic: Attention Citation: Vogeti S and Corballis PM (2013). Modulation of the face-sensitive N170 by competition between faces and their features. Conference Abstract: ACNS-2013 Australasian Cognitive Neuroscience Society Conference. doi: 10.3389/conf.fnhum.2013.212.00144 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 25 Sep 2013; Published Online: 25 Nov 2013. * Correspondence: Miss. Sreekari Vogeti, The University of Auckland, Auckland, New Zealand, svog576@aucklanduni.ac.nz Dr. Paul M Corballis, The University of Auckland, Auckland, New Zealand, p.corballis@auckland.ac.nz Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Sreekari Vogeti Paul M Corballis Google Sreekari Vogeti Paul M Corballis Google Scholar Sreekari Vogeti Paul M Corballis PubMed Sreekari Vogeti Paul M Corballis Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Single-Unit Responses Selective for Whole Faces in the Human Amygdala

The human amygdala is critical for social cognition from faces, as borne out by impairments in recognizing facial emotion following amygdala lesions [1] and differential activation of the amygdala by faces [2-5]. Single-unit recordings in the primate amygdala have documented responses selective for faces, their identity, or emotional expression [6, 7], yet how the amygdala represents face information remains unknown. Does it encode specific features of faces that are particularly critical for recognizing emotions (such as the eyes), or does it encode the whole face, a level of representation that might be the proximal substrate for subsequent social cognition? We investigated this question by recording from over 200 single neurons in the amygdalae of seven neurosurgical patients with implanted depth electrodes [8]. We found that approximately half of all neurons responded to faces or parts of faces. Approximately 20% of all neurons responded selectively only to the whole face. Although responding most to whole faces, these neurons paradoxically responded more when only a small part of the face was shown compared to when almost the entire face was shown. We suggest that the human amygdala plays a predominant role in representing global information about faces, possibly achieved through inhibition between individual facial features.

ERP evidence for the speed of face categorization in the human brain: Disentangling the contribution of low-level visual cues from face perception

How fast are visual stimuli categorized as faces by the human brain? Because of their high temporal resolution and the possibility to record simultaneously from the whole brain, electromagnetic scalp measurements should be the ideal method to clarify this issue. However, this question remains debated, with studies reporting face-sensitive responses varying from 50 ms to 200 ms following stimulus onset. Here we disentangle the contribution of the information associated with the phenomenological experience of a face (phase) from low-level visual cues (amplitude spectrum, color) in accounting for early face-sensitivity in the human brain. Pictures of faces and of a category of familiar objects (cars), as well as their phase-scrambled versions, were presented to fifteen human participants tested with high-density (128 channels) EEG. We replicated an early face-sensitivity – larger response to pictures of faces than cars – at the level of the occipital event-related potential (ERP) P1 (80–100 ms). However, a similar larger P1 to phase-scrambled faces than phase-scrambled cars was also found. In contrast, the occipito-temporal N170 was much larger in amplitude for pictures of intact faces than cars, especially in the right hemisphere, while the small N170 elicited by phase-scrambled stimuli did not differ for faces and cars. These findings show that sensitivity to faces on the visual evoked potentials P1 and N1 (N170) is functionally dissociated: the P1 face-sensitivity is driven by low-level visual cues while the N1 (or N170) face-sensitivity reflects the perception of a face. Altogether, these observations indicate that the earliest access to a high-level face representation, that is, a face percept, does not precede the N170 onset in the human brain. Furthermore, they allow resolving apparent discrepancies between the timing of rapid human saccades towards faces and the early activation of high-level facial representations as shown by electrophysiological studies in the primate brain. More generally, they put strong constraints on the interpretation of early (before 100 ms) face-sensitive effects in the human brain.

Temporal dissociation of spatial attention and competition effects between face representations

Scalp event-related potential (ERP) studies in humans indicate that the processing of faces differs from other categories between 130 and 170 ms after stimulus onset, peaking at the occipito-temporal N170. We have recently shown that the N170 response to a face stimulus is strongly reduced when another face - or a non-face object of expertise (Rossion, Kung & Tarr, 2004) - is processed concurrently (Jacques & Rossion, 2004), suggesting that neural representations of individual faces compete in the occipito-temporal cortex. However, this amplitude reduction of the N170 may be related to spatial attentional modulations rather than to a competition between face representations. To test this alternative hypothesis, ERP responses to a lateralized face were recorded while subjects were processing a centrally presented stimulus, either a face or a phase-scrambled face stimulus. Subjects performed either a low-level matching task on the central stimulus - thus allocating minimal attention to the lateralized face -, or a task in which they had to detect the occurrence of the lateralized faces. The results are twofold: first, replicating our previous results, the N170 to the lateralized face was largely reduced, starting at about 130 ms, when the central stimulus was a face relative to the control stimulus. Importantly, this competition effect was of similar amplitude in both attentional conditions. Second, when subjects concentrated on the central stimulus, the N170 to the lateral face was strongly reduced, whether the central stimulus was a face or a scrambled face, i.e. the effects of competition and spatial attention were additive on the N170. Moreover and most importantly, this effect of spatial attention started at about 80 ms after stimulus onset, on the visual P1, much earlier than the competition effect. These results indicate that spatial attention and object competition are distinct mechanisms that both strongly shape the processing of faces in extrastriate cortex.

Faces Attract Infants' Attention in Complex Displays.

Infant's face preferences have previously been assessed in displays containing 1 or 2 faces. Here we present 6-month-old infants with a complex visual array containing faces among multiple visual objects. Despite the competing objects, infants direct their first saccade toward faces more frequently than expected by chance (Experiment 1). The attention-grabbing effect of faces is not selective to upright faces (Experiment 2) but does require the presence of internal facial elements, as faces whose interior has been phase-scrambled did not attract infants' attention (Experiment 3). On the contrary, when the number of fixations is considered, upright faces are scanned more extensively than both inverted and phase-scrambled faces. The difference in selectivity between the first look measure and the fixation count measure is discussed in light of a distinction between attention-grabbing and attention-holding mechanisms.

Perceptual learning modifies inversion effects for faces and textures

We trained subjects to identify either upright or inverted faces in a 10AFC task and measured performance subsequently in four conditions: same- and different-upright faces, and same- and different-inverted faces. Performance improved for both the upright-trained and the inverted-trained groups. The improvements were highly specific to the trained face exemplars, and largely specific to the trained face orientations. This pattern of results yielded an increase in the face-inversion effect after upright-training, and a decrease in the inversion effect after inverted-training, but only for the trained set of faces in both groups. A similar pattern of results was found for phase-scrambled faces in which the configural structure of faces had been removed: although there was no baseline inversion effect for the scrambled stimuli, inversion effects emerged after training. We consider the implications of this pattern of learning for current views on the face-inversion effect, and face-encoding more generally.

Retinotopic and non-retinotopic stimulus encoding in binocular rivalry and the involvement of feedback

Adaptation is one of the key constituents of the perceptual alternation process during binocular rivalry, as it has been shown that preadapting one of the rivaling pairs before rivalry onset biases perception away from the adapted stimulus during rivalry. We investigated the influence of retinotopic and spatiotopic preadaptation on binocular rivalry. We show that for grating stimuli, preadaptation only influences rivalry when adaptation and rivalry locations are retinotopically matched. With more complex house and face stimuli, effects of preadaptation are found for both retinotopic and spatiotopic preadaptation, showing the importance of spatiotopic encoding in binocular rivalry. We show, furthermore, that adaptation to phase-scrambled faces results in retinotopic effects only, demonstrating the importance of form content for spatiotopic adaptation effects, as opposed to spatial frequency content. Are the spatiotopic adaptation influences on rivalry caused by direct spatiotopic stimulus interactions, or instead are they due to altered feedback from the adapted spatiotopic representations to the retinotopic representations that are involved in rivalry? By using rivaling face and grating stimuli that minimize rivalry between spatiotopic representations while still engaging these representations in stimulus encoding, we show that at least part of the preadaptation effects with face stimuli depend on feedback information.

Faces attract infants' attention in complex displays

Infant's face preferences have previously been assessed in displays containing 1 or 2 faces. Here we present 6-month-old infants with a complex visual array containing faces among multiple visual objects. Despite the competing objects, infants direct their first saccade toward faces more frequently than expected by chance (Experiment 1). The attention-grabbing effect of faces is not selective to upright faces (Experiment 2) but does require the presence of internal facial elements, as faces whose interior has been phase-scrambled did not attract infants' attention (Experiment 3). On the contrary, when the number of fixations is considered, upright faces are scanned more extensively than both inverted and phase-scrambled faces. The difference in selectivity between the first look measure and the fixation count measure is discussed in light of a distinction between attention-grabbing and attention-holding mechanisms.