Holistic processing of faces: learning effects with Mooney faces

The specialness of faces is seen in the face inversion effect, which disrupts the configural, but not the analytic, processing of faces. Mooney faces, which are processed holistically, allowed us to determine the contribution of holistic processing to the face inversion effect. As inverted Mooney faces are difficult to recognize as faces, we also included an intermediary training period for Mooney face recognition for half of the subjects. Early face-sensitive ERPs (N170 and P1) and P2 were measured. Behavioral data showed an increase in correct responses to inverted and upright Mooney faces after the learning phase for the experimental group. No effects were seen on P1. N170 latency did not vary with stimulus type before the intermediary phase, however, N170 amplitude was consistently larger for upright than inverted Mooney faces. After the intermediary exercise, N170 was delayed for inverted compared to upright Mooney faces. In contrast, for both groups of subjects P2 amplitude was larger for nonface stimuli, and P2 amplitude decreased after the intermediate task only for the subjects trained to recognize Mooney faces.As the usual inversion effect seen with photographic faces (delayed and larger N170) was not seen with Mooney faces, these data suggest that this effect on N170 is due to the recruitment of analytic processing. P2 reflected learning and a deeper processing of the stimuli that were not identifiable as faces.     

Cortical sensitivity to contrast polarity and orientation of faces is modulated by temporal-nasal hemifield asymmetry

Behavioral studies demonstrate that the efficiency of detection of faces is dependent on configural and contrast polarity information characteristic to human faces. Stimulus inversion or contrast polarity reversal can disrupt this process. We investigated whether a face-sensitive event-related potential component, the N170, is modulated by the orientation and contrast polarity of highly degraded schematic face-like patterns (Experiment 1) in the same manner as it is for face photographs (Experiment 2). Inversion and/or contrast reversal delayed and enhanced the N170 for both kinds of stimuli, suggesting that a white oval with three black squares is sufficient to elicit face-sensitive cortical responses. In Experiment 3 we further tested whether the extrageniculate visual pathways modulate early cortical responses to faces. We found that the N170 responses to configural and contrast information are modulated by temporal-nasal visual field asymmetry under monocular viewing conditions, suggesting the involvement of subcortical, extrageniculate visual pathways in face detection. These results are consistent with the idea that an ontogenetically early and primitive bias to orient towards face-like patterns with relevant configural and contrast information influences the early stages of cortical face processing.     

Altered face inversion effect and association between face N170 reduction and social dysfunction in patients with schizophrenia

ObjectiveThere is accumulating evidence that schizophrenics may have deficits in facial recognition, which has been related to disease-specific disturbances in normal social interaction. Neurophysiologically, face inversion results in an amplitude increase of the event-related potential (ERP) component N170. This face inversion effect (FIE) presumably reflects a disruption of face-specific configuration processing. The present study investigated FIE and the associations between social functioning and N170 in patients with schizophrenia.MethodsThe subjects consisted of 15 schizophrenics and 15 controls. Event-related potentials (ERPs) to upright and inverted neutral faces and cars were recorded. The relationships between the Social Functioning Scale (SFS) scores and N170 amplitude to upright faces or cars were also evaluated.ResultsNormal controls exhibited a significant FIE of the N170 amplitude, while schizophrenics showed no FIE. In both normal controls and schizophrenics, no inversion effect was observed for car stimuli. For face stimuli, schizophrenics showed significant bilateral N170 reduction; additionally, in schizophrenics, but not in controls, the SFS was significantly correlated with N170 amplitudes to upright faces.ConclusionsThese results indicate face-specific configuration processing deficits and significant associations between face-N170 reduction and social dysfunction in schizophrenia.SignificanceAbnormal face-specific configuration processing may underlie some of the social dysfunctions in schizophrenia.     

Do you see what I feel? – Electrophysiological correlates of emotional face and body perception in schizophrenia

ObjectiveWe aimed to elucidate whether impaired affective face processing – behaviourally and with regard to P100 and N170 components – is paralleled by similar deficits in body processing in schizophrenia. Furthermore, we aimed to assess modulations by the processing of emotional or personal identity of the stimuli.MethodsFourteen patients with schizophrenia and 15 healthy controls were assessed with a Delayed Matching-to-Sample Task involving variations of the emotional (same vs. different valence) and personal identity (same vs. different person) of bodies and faces.ResultsPatients showed overall poorer behavioural performance. In controls, P100 amplitudes were enhanced in the “same identity/different emotions” vs. “same identity/same emotion” condition and N170 amplitudes were larger for different vs. same emotions. In the patients, P100 amplitudes were enhanced in the right relative to the left hemisphere for faces, but not for bodies.ConclusionsPatients with schizophrenia show deficient modulation of the P100 and N170 components by emotional and personal identity of faces and bodies, which may relate to deficient context processing.SignificanceOur findings suggest for the first time alterations of the electrophysiological correlates of body processing in schizophrenia.     

老年抑郁症患者面孔知觉早期加工的事件相关电位研究

目的 采用事件相关电位技术,探讨老年抑郁症患者面孔识别(区分面孔还是非面孔)和面孔结构信息早期加工的脑电生理机制.方法 被试者包括19例老年抑郁症患者(患者组)及17名健康老年人(对照组).要求被试者观看图片并计数蝴蝶(靶刺激)呈现次数,其他图片(包括面孔、非面孔)为非靶刺激.记录32导脑电波.结果 (1)患者组非靶刺激诱发的P＜,1＞[(3.9±0.8)μV]和N170波幅[(-10.1±1.1)μV]均低于对照组[P<,1>:(6.8±0.8)μV;N170:(-14.4±1.1)μV;P＜0.05～0.01];(2)患者组和对照组均产生显著的N170效应(Nd170)以及N170翻转效应(倒立面孔图像时的N170变化),但患者组右侧颢枕区的N170效应[(-5.8 4±0.9)μV]弱于对照组[(-8.8±0.9)μV,P＜0.05],翻转效应的组间差异则无统计学意义(P＞0.05);(3)患者组靶刺激的P＜,3＞潜伏期[(400 ±10)ms]长于对照组[(368±10)ms;P＜0.05].结论 老年抑郁症患者可能存在面孔基本水平(区分面孔还是非面孔)早期识别的损害,而对面孔结构信息的早期加工则保持相对完整.     

Structural encoding of human and schematic faces: holistic and part-based processes

The range of specificity and the response properties of the extrastriate face area were investigated by comparing the N170 event-related potential (ERP) component elicited by photographs of natural faces, realistically painted portraits, sketches of faces, schematic faces, and by nonface meaningful and meaningless visual stimuli. Results showed that the N170 distinguished between faces and nonface stimuli when the concept of a face was clearly rendered by the visual stimulus, but it did not distinguish among different face types: Even a schematic face made from simple line fragments triggered the N170. However, in a second experiment, inversion seemed to have a different effect on natural faces in which face components were available and on the pure gestalt-based schematic faces: The N170 amplitude was enhanced when natural faces were presented upside down but reduced when schematic faces were inverted. Inversion delayed the N170 peak latency for both natural and schematic faces. Together, these results suggest that early face processing in the human brain is subserved by a multiple-component neural system in which both whole-face configurations and face parts are processed. The relative involvement of the two perceptual processes is probably determined by whether the physiognomic value of the stimuli depends upon holistic configuration, or whether the individual components can be associated with faces even when presented outside the face context.     

Effects of face inversion on the structural encoding and recognition of faces. Evidence from event-related brain potentials

It was investigated how face inversion affects face-specific components of event-related brain potentials (ERPs) which are assumed to reflect the structural encoding and the recognition of faces. ERPs were recorded to upright and inverted photographs of familiar faces, unfamiliar faces, and houses. In Part I, participants had to detect infrequently presented targets (hands), in Part II, attention was either directed towards or away from the pictorial stimuli. When compared with upright unfamiliar faces, upright familiar faces elicited an enhanced negativity between 300 ms and 450 ms ('N400f') and an enhanced positivity between 450 and 650 ms post-stimulus ('P600f'). It is suggested that these ERP modulations are generated by processes involved in the recognition of faces. Face inversion is known to disrupt face recognition processes. Accordingly, 'N400f' and 'P600f' were generally absent in response to inverted familiar and unfamiliar faces. The face-specific N170 component at lateral posterior electrodes was not affected by face familiarity, indicating that it reflects processing stages prior to face identification. N170 was delayed and enhanced for inverted relative to upright faces. While N170 enhancements were also observed for inverted relative to upright houses, the N170 latency shift caused by stimulus inversion was face-specific. Directing attention away from the faces towards a demanding primary visual task resulted in an N170 delay for inverted as well as for upright faces, suggesting that the time course of structural encoding of faces is affected by attentional factors. These results demonstrate that ERPs can be used as electrophysiological markers of specialised brain processes underlying the structural encoding and subsequent recognition of faces.     

Featural and configural face processing strategies: evidence from a functional magnetic resonance imaging study

We explored the processing mechanisms of featural and configural face information using event-related functional magnetic resonance imaging. Featural information describes the information contained in the facial parts; configural information conveys the spatial interrelationship between parts. In a delayed matching-to-sample task, participants decided whether an intact test face matched a precedent scrambled or blurred cue face. Scrambled faces primarily contain featural information whereas blurred faces preserve configural information. Scrambled cue faces evoked enhanced activation in the left fusiform gyrus, left parietal lobe, and left lingual gyrus when viewing intact test faces. Following blurred cue faces, test faces enhanced activation bilaterally in the middle temporal gyrus. The results suggest that featural and configural information is processed by following distinct neural pathways.     

Early face processing specificity: it's in the eyes!

Unlike most other objects that are processed analytically, faces are processed configurally. This configural processing is reflected early in visual processing following face inversion and contrast reversal, as an increase in the N170 amplitude, a scalp-recorded event-related potential. Here, we show that these face-specific effects are mediated by the eye region. That is, they occurred only when the eyes were present, but not when eyes were removed from the face. The N170 recorded to inverted and negative faces likely reflects the processing of the eyes. We propose a neural model of face processing in which face- and eye-selective neurons situated in the superior temporal sulcus region of the human brain respond differently to the face configuration and to the eyes depending on the face context. This dynamic response modulation accounts for the N170 variations reported in the literature. The eyes may be central to what makes faces so special.     

Losing your head: behavioral and electrophysiological effects of body inversion

The present study aimed to further explore the mechanisms underlying the perception of human body shapes. Behavioral and electrophysiological inversion effects were studied for human bodies with and without heads and for animal bodies (cats, dogs, and birds). Recognition of human bodies (with heads) was adversely affected by stimulus inversion, and the N170 had longer latencies and higher amplitudes for inverted compared to upright human bodies. Human body shapes presented without heads yielded the opposite result pattern. The data for animal bodies did not yield consistent effects. Taken together, the present findings suggest that human bodies might be processed by specialized cortical mechanisms which are at least partly dissociable from mechanisms involved in object or face processing.     

Category-sensitivity in the N170 range: a question of topography and inversion, not one of amplitude

Event-related potential studies have identified the N170 as the key neurophysiological marker of human face processing. This functional association relies on the observation of a larger N170 amplitude to faces than items from all other visual object categories. However, N170 amplitude is modulated by stimulus variations like viewpoint, size and symmetry, and studies comparing similarly sized and symmetric full-front faces and other objects have failed to find amplitude differences. Here we tested whether the effect of inversion - an increase in N170 amplitude seen for faces presented upside down - is similarly observed for full-front views of cars. Participants discriminated pictures of faces and cars, which were presented upright and inverted, and either in full-front view or varying in size, orientation and viewpoint. For upright stimuli, the N170 was stronger for faces than cars at some electrode sites, but of comparable amplitude at others, as shown by topographical differences. The N170 for inverted faces and cars was delayed, with a stronger delay for faces than cars. Inversion increased N170 amplitude for faces, while modulations for full-front view cars were non-significant or N170 amplitude was reduced. These results further limit the widely acknowledged principle of an association between N170 and visual object categorization. Potential face-sensitivity in the N170 range may therefore rely on topographic differences and effects of inversion, rather than amplitude differences.     

EEG correlates of categorical and graded face perception

Face perception is a critical social ability and identifying its neural correlates is important from both basic and applied perspectives. In EEG recordings, faces elicit a distinct electrophysiological signature, the N170, which has a larger amplitude and shorter latency in response to faces compared to other objects. However, determining the face specificity of any neural marker for face perception hinges on finding an appropriate control stimulus. We used a novel stimulus set consisting of 300 images that spanned a continuum between random patches of natural scenes and genuine faces, in order to explore the selectivity of face-sensitive ERP responses with a model-based parametric stimulus set. Critically, our database contained “false alarm” images that were misclassified as face by computational face-detection system and varied in their image-level similarity to real faces. High-density (128-channel) event-related potentials (ERPs) were recorded while 23 adult subjects viewed all 300 images in random order, and determined whether each image was a face or non-face. The goal of our analyses was to determine the extent to which a gradient of sensitivity to face-like structure was evident in the ERP signal. Traditional waveform analyses revealed that the N170 component over occipitotemporal electrodes was larger in amplitude for faces compared to all non-faces, even those that were high in image similarity to faces, suggesting strict selectivity for veridical face stimuli. By contrast, single-trial classification of the entire waveform measured at the same sensors revealed that misclassifications of non-face patterns as faces increased with image-level similarity to faces. These results suggest that individual components may exhibit steep selectivity, but integration of multiple waveform features may afford graded information regarding stimulus appearance.     

The N170 occipito-temporal component is delayed and enhanced to inverted faces but not to inverted objects: an electrophysiological account of face-specific processes in the human brain

Behavioral studies have shown that picture-plane inversion impacts face and object recognition differently, thereby suggesting face-specific processing mechanisms in the human brain. Here we used event-related potentials to investigate the time course of this behavioral inversion effect in both faces and novel objects. ERPs were recorded for 14 subjects presented with upright and inverted visual categories, including human faces and novel objects (Greebles). A N170 was obtained for all categories of stimuli, including Greebles. However, only inverted faces delayed and enhanced N170 (bilaterally). These observations indicate that the N170 is not specific to faces, as has been previously claimed. In addition, the amplitude difference between faces and objects does not reflect face-specific mechanisms since it can be smaller than between non-face object categories. There do exist some early differences in the time-course of categorization for faces and non-faces across inversion. This may be attributed either to stimulus category per se (e.g. face-specific mechanisms) or to differences in the level of expertise between these categories.     

The neural correlates of perceiving human bodies: an ERP study on the body-inversion effect

The present study investigated the neural correlates of perceiving human bodies. Focussing on the N170 as an index of structural encoding, we recorded event-related potentials (ERPs) to images of bodies and faces (either neutral or expressing fear) and objects, while subjects viewed the stimuli presented either upright or inverted. The N170 was enhanced and delayed to inverted bodies and faces, but not to objects. The emotional content of faces affected the left N170, the occipito-parietal P2, and the fronto-central N2, whereas body expressions affected the frontal vertex positive potential (VPP) and a sustained fronto-central negativity (300-500 ms). Our results indicate that, like faces, bodies are processed configurally, and that within each category qualitative differences are observed for emotional as opposed to neutral images.     

ERP evidence of developmental changes in processing of faces.

OBJECTIVES: There is disagreement in the behavioural literature, as to whether face processing undergoes qualitative or quantitative change with age. METHODS: We studied event-related potentials (ERPs) associated with facial processing in 48 children (4-14 years) and 12 adults. Five categories of stimuli were presented: faces, cars, scrambled faces, scrambled cars, butterflies. The butterflies were targets (P = 12%); the other stimulus categories were equally represented and all were non-targets. RESULTS: An N170 was recorded only to the faces at posterior temporal sites and in adults it was largest at T6'. This component was seen across age groups, but at steadily increasing latencies in younger children. Age-related increases in N170 amplitude were found at T6'. In children under 12 years of age, the frontal P170 was not reliably seen. CONCLUSION: This study suggests that the underlying neural basis associated with processing faces matures in a gradual, quantitative manner throughout childhood.     

Face and body perception in schizophrenia: A configural processing deficit?

Face and body perception rely on common processing mechanisms and activate similar but not identical brain networks. Patients with schizophrenia show impaired face perception, and the present study addressed for the first time body perception in this group. Seventeen patients diagnosed with schizophrenia or schizoaffective disorder were compared to 17 healthy controls on standardized tests assessing basic face perception skills (identity discrimination, memory for faces, recognition of facial affect). A matching-to-sample task including emotional and neutral faces, bodies and cars either in an upright or in an inverted position was administered to assess potential category-specific performance deficits and impairments of configural processing. Relative to healthy controls, schizophrenia patients showed poorer performance on the tasks assessing face perception skills. In the matching-to-sample task, they also responded more slowly and less accurately than controls, regardless of the stimulus category. Accuracy analysis showed significant inversion effects for faces and bodies across groups, reflecting configural processing mechanisms; however reaction time analysis indicated evidence of reduced inversion effects regardless of category in schizophrenia patients. The magnitude of the inversion effects was not related to clinical symptoms. Overall, the data point towards reduced configural processing, not only for faces but also for bodies and cars in individuals with schizophrenia.     

Eyes first! Eye processing develops before face processing in children.

Faces and eyes are critical social stimuli which adults process with ease, but how this expertise develops is not yet understood. Neural changes associated with face and eye processing were investigated developmentally using ERPs (N170), in 128 subjects (4-15 year olds and adults). Stimuli included upright faces to assess configural processing, eyes and inverted faces to assess feature-based processing. N170 was present in the youngest children with similar patterns of face sensitivity seen in adults. Development of N170 to upright faces continued until adulthood, suggesting slow maturation of configural processing. In contrast, N170 was shorter latency and much larger to eyes than faces in children and was mature by 11 years, suggesting the early presence of an eye detector, with a rapid maturational course.     

Cognitive behavioural therapy attenuates the enhanced early facial stimuli processing in social anxiety disorders: an ERP investigation

Background

Previous studies of patients with social anxiety have demonstrated abnormal early processing of facial stimuli in social contexts. In other words, patients with social anxiety disorder (SAD) tend to exhibit enhanced early facial processing when compared to healthy controls. Few studies have examined the temporal electrophysiological event-related potential (ERP)-indexed profiles when an individual with SAD compares faces to objects in SAD. Systematic comparisons of ERPs to facial/object stimuli before and after therapy are also lacking. We used a passive visual detection paradigm with upright and inverted faces/objects, which are known to elicit early P1 and N170 components, to study abnormal early face processing and subsequent improvements in this measure in patients with SAD.

Methods

Seventeen patients with SAD and 17 matched control participants performed a passive visual detection paradigm task while undergoing EEG. The healthy controls were compared to patients with SAD pre-therapy to test the hypothesis that patients with SAD have early hypervigilance to facial cues. We compared patients with SAD before and after therapy to test the hypothesis that the early hypervigilance to facial cues in patients with SAD can be alleviated.

Results

Compared to healthy control (HC) participants, patients with SAD had more robust P1–N170 slope but no amplitude effects in response to both upright and inverted faces and objects. Interestingly, we found that patients with SAD had reduced P1 responses to all objects and faces after therapy, but had selectively reduced N170 responses to faces, and especially inverted faces. Interestingly, the slope from P1 to N170 in patients with SAD was flatter post-therapy than pre-therapy. Furthermore, the amplitude of N170 evoked by the facial stimuli was correlated with scores on the interaction anxiousness scale (IAS) after therapy.

Conclusions

Our results did not provide electrophysiological support for the early hypervigilance hypothesis in SAD to faces, but confirm that cognitive-behavioural therapy can reduce the early visual processing of faces. These findings have potentially important therapeutic implications in the assessment and treatment of social anxiety. Trial registration HEBDQ2014021

     

Dissociation between recognition of familiar scenes and of faces in patients with very mild Alzheimer disease: An event-related potential study

ObjectiveWe used event-related potentials (ERPs) to examine the recognition of familiar faces and scenes in patients with very mild Alzheimer disease (VMAD).MethodsTwo types of stimuli, FACEs and SCENEs, and two versions of each type, FAMILIAR and NOVEL, were presented. Three ERPs were compared between VMAD and normal control (NC): (1) P100 to examine basic visual processing, (2) N170 structural encoding, and (3) N250r familiarity.ResultsA prominent N170 was elicited by FACEs in P8 and the largest N170 by SCENEs in P3 and P4. Participants had more errors when judging pictures of SCENEs as familiar or not than that of FACEs. In P3 and P4, NC produced larger N170 than VMAD. From N250r in F3, the familiarity effect was absent in VMAD when familiar scenes were provided. This deficit was not seen in processing familiar faces.ConclusionsThis study shows that different neural regions are responsible for the early visual processing in the structural encoding of scenes and faces. The pattern of P100 and that of N170 suggest that VMAD patients maintain basic visual processing and structural encoding abilities. A conflict between behavioral and physiological responses may play a role in VMAD patients’ risk of getting lost in familiar environments.SignificanceScene recognition is impaired earlier than face recognition in the course of Alzheimer disease.     

Cortical deficits of emotional face processing in adults with ADHD: its relation to social cognition and executive function

Although it has been shown that adults with attention-deficit hyperactivity disorder (ADHD) have impaired social cognition, no previous study has reported the brain correlates of face valence processing. This study looked for behavioral, neuropsychological, and electrophysiological markers of emotion processing for faces (N170) in adult ADHD compared to controls matched by age, gender, educational level, and handedness. We designed an event-related potential (ERP) study based on a dual valence task (DVT), in which faces and words were presented to test the effects of stimulus type (faces, words, or face-word stimuli) and valence (positive versus negative). Individual signatures of cognitive functioning in participants with ADHD and controls were assessed with a comprehensive neuropsychological evaluation, including executive functioning (EF) and theory of mind (ToM). Compared to controls, the adult ADHD group showed deficits in N170 emotion modulation for facial stimuli. These N170 impairments were observed in the absence of any deficit in facial structural processing, suggesting a specific ADHD impairment in early facial emotion modulation. The cortical current density mapping of N170 yielded a main neural source of N170 at posterior section of fusiform gyrus (maximum at left hemisphere for words and right hemisphere for faces and simultaneous stimuli). Neural generators of N170 (fusiform gyrus) were reduced in ADHD. In those patients, N170 emotion processing was associated with performance on an emotional inference ToM task, and N170 from simultaneous stimuli was associated with EF, especially working memory. This is the first report to reveal an adult ADHD-specific impairment in the cortical modulation of emotion for faces and an association between N170 cortical measures and ToM and EF.