Interplay between familiarity and orientation in face processing: An ERP study

Indistinguishable behavioural and neural correlates of perceptual self-other distinction in autistic and neurotypical adults

Previous research has suggested that self-bias (i.e., enhanced cognitive processing of self-versus other-relevant information) may be atypical in autism spectrum conditions (ASC), perhaps due to difficulties with self-other distinction. However, empirical evidence for this is inconsistent, and the neural basis of processing differences remains unknown. We present two experiments that aimed to test perceptual self-bias and familiarity effects in ASC using a perceptual-association task. Participants were asked to distinguish face/label associations of the self from those of other people of differing levels of familiarity (i.e., friend vs stranger). Experiment 1 took an individual differences approach by testing whether behavioural self-bias is associated with the number of autistic traits in a neurotypical adult sample (N = 59). Experiment 2 took a case-control approach by testing whether behavioural self-bias and associated ERP responses differ between neurotypical (N = 27) and autistic (N = 30) adults. Across both experiments, behavioural results showed that participants experienced a self-bias (self > friend and stranger) and a familiarity effect (e.g., friend > stranger); neither effect was affected by the number of autistic traits or autism diagnosis. In Experiment 2, analysis of N1, N2, and P3 ERP components revealed a typical self-bias in both groups (self distinct from friend and stranger), and only the autistic group showed evidence of a familiarity effect (N2 more negative-going for stranger than friend). The findings are discussed in relation to self-other distinction ability, and the relevance of other neuropsychological and psychiatric conditions such as anxiety and alexithymia are also considered.

Effect of inverted faces as visual stimuli on the performance of the hybrid SSVEP + P300 brain computer interface

INTRODUCTION

This study proposes a hybrid brain-computer interface (BCI) system that simultaneously evokes steady-state visual evoked potentials (SSVEP) and event-related potentials (P300). The goal of this study was to improve the performance of the current hybrid SSVEP + P300 BCI systems by incorporating inverted faces into visual stimuli.

METHODS

In this study, upright and inverted faces were added to visual stimulus to elicit stronger cortical responses in a hybrid SSVEP + P300 BCI. We also considered triggering the P300 signals with facial stimuli and the SSVEP signals with non-facial stimuli. We have tested four paradigms: the upright face paradigm (UF), the inverted face paradigm (IF), the upright face and flicker paradigm (UFF), and the inverted face and flicker paradigm (IFF).

RESULTS AND CONCLUSIONS

The results showed that the IFF paradigm evoked more robust cortical responses, which led to enhanced system accuracy and ITR. The IFF paradigm had an average accuracy of 96.6% and a system communication rate of 26.45 bits per second. The UFF paradigm is the best candidate for BCI applications among other paradigms because it provides maximum comfort while maintaining a reasonable ITR.

Using transcranial direct current stimulation (tDCS) to selectively modulate the face inversion effect and N170 event-related potentials

We report a large study (n = 72) using combined transcranial direct current stimulation-electroencephalography (tDCS-EEG) to investigate the modulation of perceptual learning indexed by the face inversion effect. Participants were engaged with an old/new recognition task involving intermixed upright and inverted, normal and Thatcherized faces. The accuracy results showed anodal tDCS delivered at the Fp3 scalp area (cathode/reference electrode placed at Fp2) increased the behavioural inversion effect for normal faces versus sham/control and this covaried with a modulation of the N170 event-related potential component. A reduced inversion effect for normal faces was found on the N170 latency and amplitude versus sham/control, extending recent work that combined tDCS and EEG in circumstances where the behavioural face inversion effect was reduced. Our results advance understanding of the neural mechanisms responsible for perceptual learning by revealing a dissociation between the N170 amplitude and latency in response to the tDCS-induced modulation of the face inversion effect. The behavioural modulation of the inversion effect tracks the modulation of the N170 amplitudes, albeit it is negatively correlated (i.e., reduced inversion effect-larger N170 amplitude inversion effect, increased inversion effect-reduced N170 amplitude inversion effect). For the N170 latencies, the inversion effect is reduced by the tDCS protocol we use irrespective of any modulation of the behavioural inversion effect.

High familiar faces have both eye recognition and holistic processing advantages

People recognize familiar faces better than unfamiliar faces. However, it remains unknown whether familiarity affects part-based and/or holistic processing. Wang et al., Frontiers in Psychology, 6, 559 (2015), Vision Research, 157, 89-96 (2019) found both enhanced part-based and holistic processing in eye relative to mouth regions (i.e., in a region-selective manner) for own-race and own-species faces, i.e., faces with more experience. Here, we examined the role of face familiarity in eyes (part-based, region-selective) and holistic processing. Face familiarity was tested at three levels: high-familiar (faces of students from the same department and the same class who attended almost all courses together), low-familiar (faces of students from the same department but different classes who attended some courses together), and unfamiliar (faces of schoolmates from different departments who seldom attended the same courses). Using the old/new task in Experiment 1, we found that participants recognized eyes of high-familiar faces better than low-familiar and unfamiliar ones, while similar performance was observed for mouths, indicating a region-selective, eyes familiarity effect. Using the "Perceptual field" paradigm in Experiment 2, we observed a stronger inversion effect for high-familiar faces, a weaker inversion effect for low-familiar faces, but a non-significant inversion effect for unfamiliar faces, indicating that face familiarity plays a role in holistic processing. Taken together, our results suggest that familiarity, like other experience-based variables (e.g., race and species), can improve both eye processing and holistic processing.

Increased N250 elicited by facial familiarity: An ERP study including the face inversion effect and facial emotion processing

The present study aims to explore how familiarity modulates the neural processing of faces under different conditions: upright or inverted, neutral or emotional. To this purpose, 32 participants (25 female; age: M = 27.7 years, SD = 9.3) performed two face/emotion identification tasks during EEG recording. In the first task, to study facial processing, three different categories of facial stimuli were presented during a target detection task: famous familiar faces, faces of loved ones, and unfamiliar faces. To explore the face inversion effect according to each level of familiarity, these facial stimuli were also presented upside down. In the second task, to study emotional face processing, an emotional identification task on personally familiar and unfamiliar faces was conducted. The behavioural results showed an improved performance in the identification of facial expressions of emotion with the increase of facial familiarity, consistent with the previous literature. Regarding electrophysiological results, we found increased amplitudes of the P100, N170, and N250 for inverted compared to upright faces, independently of their degree of familiarity. Moreover, we did not find familiarity effects at the P100 and N170 time-windows, but we found that N250 amplitude was larger for personally familiar compared to unfamiliar faces. This result supports the reasoning that the facial familiarity increases the neural activity during the N250 time-window, which may be explained by the processing of additional information prompted by the viewing of our loved ones faces, in contrast to what happens with unfamiliar individuals.

Developing familiarity during the first eight months of knowing a person: A longitudinal EEG study on face and identity learning

It is well-established that familiar and unfamiliar faces are processed differently, but surprisingly little is known about how familiarity builds up over time and how novel faces gradually become represented in the brain. Here, we used event-related brain potentials (ERPs) in a pre-registered, longitudinal study to examine the neural processes accompanying face and identity learning during the first eight months of knowing a person. Specifically, we examined how increasing real-life familiarity affects visual recognition (N250 Familiarity Effect) and the integration of person-related knowledge (Sustained Familiarity Effect, SFE). Sixteen first-year undergraduates were tested in three sessions, approximately one, five, and eight months after the start of the academic year, with highly variable "ambient" images of a new friend they had met at university and of an unfamiliar person. We observed clear ERP familiarity effects for the new friend after one month of familiarity. While there was an increase in the N250 effect over the course of the study, no change in the SFE was observed. These results suggest that visual face representations develop faster relative to the integration of identity-specific knowledge.

Neural timing of the other-race effect across the lifespan: A review

Face race influences the way we process faces, so that faces of a different ethnic group are processed for identity less efficiently than faces of one's ethnic group - a phenomenon known as the Other-Race Effect (ORE). Although widely replicated, the ORE is still poorly characterized in terms of its development and the underlying mechanisms. In the last two decades, the Event-Related Potential (ERP) technique has brought insight into the mechanisms underlying the ORE and has demonstrated potential to clarify its development. Here, we review the ERP evidence for a differential neural processing of own-race and other-race faces throughout the lifespan. In infants, race-related processing differences emerged at the N290 and P400 (structural encoding) stages. In children, race affected the P100 (early processing, attention) perceptual stage and was implicitly encoded at the N400 (semantic processing) stage. In adults, processing difficulties for other-race faces emerged at the N170 (structural encoding), P200 (configuration processing) and N250 (accessing individual representations) perceptual stages. Early in processing, race was implicitly encoded from other-race faces (N100, P200 attentional biases) and in-depth processing preferentially applied to own-race faces (N200 attentional bias). Encoding appeared less efficient (Dm effects) and retrieval less recollection-based (old/new effects) for other-race faces. Evidence admits the contribution of perceptual, attentional, and motivational processes to the development and functioning of the ORE, offering no conclusive support for perceptual or socio-cognitive accounts. Cross-racial and non-cross-racial studies provided convergent evidence. Future research would need to include less represented ethnic populations and the developmental population.

Effects of aging on face processing: An ERP study of the own-age bias with neutral and emotional faces

Older adults systematically show an enhanced N170 amplitude during the visualization of facial expressions of emotion. The present study aimed to replicate this finding, further investigating if this effect is specific to facial stimuli, present in other neural correlates of face processing, and modulated by own-age faces. To this purpose, younger (n = 25; M_age = 28.36), middle-aged (n = 23; M_age = 48.74), and older adults (n = 25; M_age = 67.36) performed two face/emotion identification tasks during an EEG recording. The results showed that groups did not differ regarding P100 amplitude, but older adults had increased N170 amplitude for both facial and non-facial stimuli. The event-related potentials analysed were not modulated by an own-age bias, but older faces elicited larger N170 in the Emotion Identification Task for all groups. This increased amplitude may reflect a higher ambiguity of older faces due to age-related changes in their physical features, which may elicit higher neural resources to decode. Regarding P250, older faces elicited decreased amplitudes than younger faces, which may reflect a reduced processing of the emotional content of older faces. This interpretation is consistent with the lower accuracy obtained for this category of stimuli across groups. These results have important social implications and suggest that aging may hamper the neural processing of facial expressions of emotion, especially for own-age peers.

Neural correlates of face familiarity in institutionalised children and links to attachment disordered behaviour

BACKGROUND

One of the most well-documented sequelae of early maltreatment and institutionalisation is attachment problems, including behaviours under the labels of reactive attachment disorder (RAD) and disinhibited social engagement disorder (DSED). Despite growing evidence of the neurobiological effects of institutionalisation, the neural correlates of these behavioural patterns are largely unknown.

METHODS

The current study examined effects of both institutionalisation in general and attachment disordered behaviour, in particular, on brain-based markers of face processing, in 100 Portuguese children (70 currently institutionalised, 30 continuously raised by their families). Children's neural processing of caregiver's and stranger's faces was assessed with Event-Related Potentials (ERPs).

RESULTS

Compared to children from the community, institutionalised children showed smaller amplitudes in the N170, to both stranger and caregiver faces. Amongst the institutionalised group, living in a setting with a higher children-to-caregivers' ratio was associated with smaller P400 amplitudes. The display of DSED symptoms was associated with a smaller P1 to both faces, as well as a reduced differentiation between faces in P400 amplitudes and smaller P400 to the stranger's face. In contrast, RAD symptoms were not associated with any ERP measures.

CONCLUSIONS

Results replicate previously reported hypoactivation in institutionalised children, in a less-globally deprived setting than past work, indicating that such a pattern is associated with lack of individualised care and increased symptoms of DSED.

Face familiarity revealed by fixational eye movements and fixation-related potentials in free viewing

Event-related potentials (ERPs) and the oculomotor inhibition (OMI) in response to visual transients are known to be sensitive to stimulus properties, attention, and expectation. We have recently found that the OMI is also sensitive to face familiarity. In natural vision, stimulation of the visual cortex is generated primarily by saccades, and it has been recently suggested that fixation-related potentials (FRPs) share similar components with the ERPs. Here, we investigated whether FRPs and microsaccade inhibition (OMI) in free viewing are sensitive to face familiarity. Observers freely watched a slideshow of seven unfamiliar and one familiar facial images presented randomly for 4-s periods, with multiple images per identity. We measured the occipital fixation-related N1 relative to the P1 magnitude as well as the associated fixation-triggered OMI. We found that the average N1-P1 was significantly smaller and the OMI was shorter for the familiar face, compared with any of the seven unfamiliar faces. Moreover, the P1 was suppressed across saccades for the familiar but not for the unfamiliar faces. Our results highlight the sensitivity of the occipital FRPs to stimulus properties such as face familiarity and advance our understanding of the integration process across successive saccades in natural vision.

Cortical activity involved in perception and imagery of visual stimuli in a subject with aphantasia. An EEG case report

Aphantasia has been described as the inability to voluntarily evoke mental images using the "mind's eye." We studied a congenital aphantasic subject using neuropsychological testsand 64 channel EEG recordings, in order to studycortical activity involved in perception and imagery evaluating event-related potentials(N170, P200, N250). The subject is in the normal range of the neuropsychological tests performed, except for specific imagery tests. The EEG results show that when he evokes the same mental image, he starts the evoking process from left temporal instead of frontal areas, he does not activate occipital visual nor left anterior parietal areas.

Developmental Differences in Neuromagnetic Cortical Activation and Phase Synchrony Elicited by Scenes with Faces during Movie Watching

The neural underpinnings of humans’ ability to process faces and how it changes over typical development have been extensively studied using paradigms where face stimuli are oversimplified, isolated, and decontextualized. The prevalence of this approach, however, has resulted in limited knowledge of face processing in ecologically valid situations, in which faces are accompanied by contextual information at multiple time scales. In the present study, we use a naturalistic movie paradigm to investigate how neuromagnetic activation and phase synchronization elicited by faces from movie scenes in humans differ between children and adults. We used MEG data from 22 adults (6 females, 3 left handed; mean age, 27.7 ± 5.28 years) and 20 children (7 females, 1 left handed; mean age, 9.5 ± 1.52 years) collected during movie viewing. We investigated neuromagnetic time-locked activation and phase synchronization elicited by movie scenes containing faces in contrast to other movie scenes. Statistical differences between groups were tested using a multivariate data-driven approach. Our results revealed lower face-elicited activation and theta/alpha phase synchrony between 120 and 330 ms in children compared with adults. Reduced connectivity in children was observed between the primary visual areas as well as their connections with higher-order frontal and parietal cortical areas. This is the first study to map neuromagnetic developmental changes in face processing in a time-locked manner using a naturalistic movie paradigm. It supports and extends the existing evidence of core face-processing network maturation accompanied by the development of an extended system of higher-order cortical areas engaged in face processing.

Inhibition of the occipital face area modulates the electrophysiological signals of face familiarity: A combined cTBS-EEG study

The occipital face area (OFA) is hierarchically one of the first stages of the face processing network. It has originally been thought to be involved in early, structural processing steps, but currently more and more studies challenge this view and propose that it also takes part in higher level face processing, such as identification and recognition. Here we tested whether the OFA is involved in the initial steps of recognition memory and plays a causal role in the differential processing of familiar and unfamiliar faces. We used an offline, inhibitory continuous theta-burst stimulation (cTBS) protocol over the right OFA and the vertex as control site. Electroencephalographic (EEG) recording of event-related potentials (ERPs), elicited by visually presented familiar (famous) and unfamiliar faces was performed before and after stimulation. We observed a difference in ERPs for famous and unfamiliar faces in a time-window corresponding to the N250 component. Importantly, this difference was significantly increased by cTBS of the right OFA, suggesting its causal role in the differential processing of familiar and unfamiliar faces. The enhancement occurred focally, at electrodes close to the right hemispheric cTBS site, as well as over similar occipito-temporal sites of the contralateral hemisphere. To the best of our knowledge, this is the first study showing the causal role of the rOFA in the differential processing of familiar and unfamiliar faces, using combined cTBS and EEG recording methods. These results are discussed with respect to the nature of familiar face representations, supported by an extensive, bilateral network.

The N170 is Sensitive to Long-term (Personal) Familiarity of a Face Identity

The N170 is a large deflection of the human electroencephalogram (EEG), peaking at about 170 milliseconds over the occipito-temporal cortex after the sudden onset of a face stimulus. The N170 reflects perceptual awareness of a face and its onset corresponds to the emergence of reliable face-selectivity in the human brain. However, whether sensitivity to the long-term familiarity of a face identity emerges already at this early time-point remains debated. Here we provide a brief survey of the 45 published studies comparing the N170 response to unfamiliar and familiar (famous, experimentally familiarized, personally familiar and own) faces. Even though effects of familiarity on the N170 are relatively small and inconsistent across studies, this overview indicates that face familiarity significantly increases the N170 amplitude. This effect is especially present for personally familiar faces, learned in natural conditions. In the human brain, effects linked to familiarity with specific facial identities therefore appear to emerge between 150 and 200 ms in occipito-temporal brain regions, i.e., shortly after the onset of face-selectivity but at the same time as the earliest high-level effects of immediate unfamiliar face identity repetition. This observation challenges standard neurocognitive models with a clear-cut distinction between perceptual and memory stages in human face recognition.

Altering sensorimotor simulation impacts early stages of facial expression processing depending on individual differences in alexithymic traits

Simulation models of facial expressions suggest that posterior visual areas and brain areas underpinning sensorimotor simulations might interact to improve facial expression processing. According to these models, facial mimicry, a manifestation of sensorimotor simulation, may contribute to the visual processing of facial expressions by influencing early stages. The aim of this study was to assess whether and how sensorimotor simulation influences early stages of face processing, also investigating its relationship with alexithymic traits given that previous studies have suggested that individuals with high levels of alexithymic traits (vs. individuals with low levels of alexithymic traits) tend to use sensorimotor simulation to a lesser extent. We monitored P1 and N170 ERP components of the event-related potentials (ERP) in participants performing a fine discrimination task of facial expressions and animals, as a control condition. In half of the experiment, participants could freely use their facial mimicry whereas in the other half they had their facial mimicry blocked by a gel. Our results revealed that only individuals with lower compared to high alexithymic traits showed a larger modulation of the P1 amplitude as a function of the mimicry manipulation selectively for facial expressions (but not for animals), while we did not observe any modulation of the N170. Given the null results at the behavioural level, we interpreted the P1 modulation as compensative visual processing in individuals with low levels of alexithymia under conditions of interference on the sensorimotor processing, providing a preliminary evidence in favor of sensorimotor simulation models.

Turning the Face Inversion Effect on Its Head: Violated Expectations of Orientation, Lighting, and Gravity Enhance N170 Amplitudes

Face inversion effects occur for both behavioral and electrophysiological responses when people view faces. In EEG, inverted faces are often reported to evoke an enhanced amplitude and delayed latency of the N170 ERP. This response has been attributed to the indexing of specialized face processing mechanisms within the brain. However, inspection of the literature revealed that, although N170 is consistently delayed to a variety of face representations, only photographed faces invoke enhanced N170 amplitudes upon inversion. This suggests that the increased N170 amplitudes to inverted faces may have other origins than the inversion of the face's structure. We hypothesize that the unique N170 amplitude response to inverted photographed faces stems from multiple expectation violations, over and above structural inversion. For instance, rotating an image of a face upside-down not only violates the expectation that faces appear upright but also lifelong priors about illumination and gravity. We recorded EEG while participants viewed face stimuli (upright vs. inverted), where the faces were illuminated from above versus below, and where the models were photographed upright versus hanging upside-down. The N170 amplitudes were found to be modulated by a complex interaction between orientation, lighting, and gravity factors, with the amplitudes largest when faces consistently violated all three expectations. These results confirm our hypothesis that face inversion effects on N170 amplitudes are driven by a violation of the viewer's expectations across several parameters that characterize faces, rather than a disruption in the configurational disposition of its features.

Configural processing of emotional bodies and faces in patients with attention deficit hyperactivity disorder

Introduction: Attention Deficit Disorder (ADHD) is associated with interpersonal problems and difficulties in inferring other peoples' emotions. Previous research has focused on face processing, mostly in children. Our study investigated configural processing of emotional bodies and faces in adults with ADHD in comparison with healthy controls, analyzing P100, N170 and P250 event-related potentials (ERPs) and relating them to (socio)cognitive functioning. Method: Nineteen patients with ADHD and 25 healthy controls were presented upright and inverted bodies and faces which had to be categorized as neutral, happy or angry while ERPs were recorded. Additionally, sociocognitive and executive functioning was assessed. Results: In ADHD patients relative to controls, recognition of emotions depicted by bodies but not by faces was impaired and P100 amplitudes were enhanced for angry bodies. Furthermore, patients showed enhanced P250 amplitudes in response to both bodies and faces, specifically for happy and neutral emotions. Larger N170 amplitudes to bodies and faces correlated with lower alexithymia scores only in controls, while enhanced P250 amplitudes to both categories were associated with poorer inhibition only in patients. Conclusion: Adults with ADHD show potentially compensatory enhanced semantic processing of emotional bodies and faces, as reflected by increased P250 amplitudes, associated with poorer executive functioning and subtle alterations of emotional and configural processing, as reflected by ERPs.

Attention is prioritised for proximate and approaching fearful faces

Attention is an important function that allows us to selectively enhance the processing of relevant stimuli in our environment. Fittingly, a number of studies have revealed that potentially threatening/fearful stimuli capture attention more efficiently. Interestingly, in separate fMRI studies, threatening stimuli situated close to viewers were found to enhance brain activity in fear-relevant areas more than stimuli that were further away. Despite these observations, few studies have examined the effect of personal distance on attentional capture by emotional stimuli. Using electroencephalography (EEG), the current investigation addressed this question by investigating attentional capture of emotional faces that were either looming/receding, or were situated at different distances from the viewer. In Experiment 1, participants carried out an incidental task while looming or receding fearful and neutral faces were presented bilaterally. A significant lateralised N170 and N2pc were found for a looming upright fearful face, however no significant components were found for a looming upright neutral face or inverted fearful and neutral faces. In Experiment 2, participants made gender judgements of emotional faces that appeared on a screen situated within or beyond peripersonal space (respectively 50 cm or 120 cm). Although response times did not differ, significantly more errors were made when faces appeared in near as opposed to far space. Importantly, ERPs revealed a significant N2pc for fearful faces presented in peripersonal distance, compared to the far distance. Our findings show that personal distance markedly affects neural responses to emotional stimuli, with increased attention towards fearful upright faces that appear in close distance.

Brain Processes While Struggling With Evidence Accumulation During Facial Emotion Recognition: An ERP Study

The human brain is tuned to recognize emotional facial expressions in faces having a natural upright orientation. The relative contributions of featural, configural, and holistic processing to decision-making are as yet poorly understood. This study used a diffusion decision model (DDM) of decision-making to investigate the contribution of early face-sensitive processes to emotion recognition from physiognomic features (the eyes, nose, and mouth) by determining how experimental conditions tapping those processes affect early face-sensitive neuroelectric reflections (P100, N170, and P250) of processes determining evidence accumulation at the behavioral level. We first examined the effects of both stimulus orientation (upright vs. inverted) and stimulus type (photographs vs. sketches) on behavior and neuroelectric components (amplitude and latency). Then, we explored the sources of variance common to the experimental effects on event-related potentials (ERPs) and the DDM parameters. Several results suggest that the N170 indicates core visual processing for emotion recognition decision-making: (a) the additive effect of stimulus inversion and impoverishment on N170 latency; and (b) multivariate analysis suggesting that N170 neuroelectric activity must be increased to counteract the detrimental effects of face inversion on drift rate and of stimulus impoverishment on the stimulus encoding component of non-decision times. Overall, our results show that emotion recognition is still possible even with degraded stimulation, but at a neurocognitive cost, reflecting the extent to which our brain struggles to accumulate sensory evidence of a given emotion. Accordingly, we theorize that: (a) the P100 neural generator would provide a holistic frame of reference to the face percept through categorical encoding; (b) the N170 neural generator would maintain the structural cohesiveness of the subtle configural variations in facial expressions across our experimental manipulations through coordinate encoding of the facial features; and (c) building on the previous configural processing, the neurons generating the P250 would be responsible for a normalization process adapting to the facial features to match the stimulus to internal representations of emotional expressions.

Testing the effects of transcranial direct current stimulation (tDCS) on the face inversion effect and the N170 event-related potentials (ERPs) component

The following study investigates the effects of tDCS on face recognition skills indexed by the face inversion effect (better recognition performance for upright vs. inverted faces). We combined tDCS and EEG simultaneously to examine the effects of tDCS on the face inversion effect behaviourally and on the N170 ERPs component. The results from two experiments (overall N = 112) show that anodal tDCS delivered at Fp3 site for 10 min at 1.5 mA (double-blind and between-subjects) can reduce behaviourally the face inversion effect compared to sham (control) stimulation. The ERP results provide some evidence for tDCS being able to influence the face inversion effect on the N170. Specifically, we find a dissociation of the tDCS-induced effects where for the N170 latencies the tDCS reduces the usual face inversion effect (delayed N170 in response to inverted vs. upright faces) compared to sham. Contrarily, the same tDCS procedure on the same participants increased the inversion effect seen in the N170 amplitudes by making the negative deflection for the inverted faces that much greater than that for upright faces. We interpret our results in the context of the literature on the face inversion effect and the N170 peak component. In doing so, we extend our results to previous studies investigating the effects of tDCS on perceptual learning and face recognition.

Perceptual and Semantic Phases of Face Identification Processing: A Multivariate Electroencephalography Study

Rapid identification of a familiar face requires an image-invariant representation of person identity. A varying sample of familiar faces is necessary to disentangle image-level from person-level processing. We investigated the time course of face identity processing using a multivariate electroencephalography analysis. Participants saw ambient exemplars of celebrity faces that differed in pose, lighting, hairstyle, and so forth. A name prime preceded a face on half of the trials to preactivate person-specific information, whereas a neutral prime was used on the remaining half. This manipulation helped dissociate perceptual- and semantic-based identification. Two time intervals within the post-face onset electroencephalography epoch were sensitive to person identity. The early perceptual phase spanned 110-228 msec and was not modulated by the name prime. The late semantic phase spanned 252-1000 msec and was sensitive to person knowledge activated by the name prime. Within this late phase, the identity response occurred earlier in time (300-600 msec) for the name prime with a scalp topography similar to the FN400 ERP. This may reflect a matching of the person primed in memory with the face on the screen. Following a neutral prime, the identity response occurred later in time (500-800 msec) with a scalp topography similar to the P600f ERP. This may reflect activation of semantic knowledge associated with the identity. Our results suggest that processing of identity begins early (110 msec), with some tolerance to image-level variations, and then progresses in stages sensitive to perceptual and then to semantic features.

Assessment of Visual Pursuit in Patients With Disorders of Consciousness Based on a Brain-Computer Interface

Visual pursuit assessment is extensively applied in the behavioral scale-based clinical examination of patients with disorders of consciousness (DOC). However, this assessment is challenging because it relies on behavioral markers, and these patients severely lack behavioral responses. Brain-computer interfaces (BCIs) may provide a potential solution to detect brain responses to external stimuli without requiring behavioral expressions. A BCI system was designed to simulate visual pursuit detection in the coma recovery scale-revised (CRS-R). The graphical user interface included four buttons, one that moved on the screen and three that did not. These buttons flashed in a random order. The patients were prompted to follow the moving button. Based on the collected electroencephalography data, the algorithm determined whether the patient focused on the moving target. Among the 14 DOC patients who participated in the assessments based on the BCI system and the CRS-R, four patients exhibited visual pursuit, and three were nonresponsive in both assessments. More importantly, seven patients who did not exhibit visual pursuit in CRS-R were detected to be responsive to the moving target stimuli in the BCI assessment. Furthermore, five out of seven recovered consciousness to some degree and showed visual pursuit in the second CRS-R assessment. The proposed BCI system is better able to detect visual pursuit than the behavioral scale-based assessment and thus can assist in clinically evaluating the challenging population of DOC patients.

Efecto de la empatía afectiva sobre el procesamiento cortical de emojis

Objetivo. Identificar las diferencias en el procesamiento cortical de emojis en personas con alta y baja empatía afectiva. Método. El estudio se llevó a cabo con 69 participantes, distribuidos en dos grupos –baja y alta empatía afectiva–, según su puntaje en el Índice de Reactividad Interpersonal. Cada participante observó emojis con expresiones de alegría, ira y neutros. Se registraron los potenciales relacionados a eventos (PRE) P100, N170 y LPP. Resultados. Se encontró una mayor amplitud del N170 en el grupo de personas con alta empatía afectiva y, en general, mayor magnitud del LPP ante emojis de ira. Conclusión. Los resultados sugieren que los emojis son procesados corticalmente de forma similar al rostro humano y que la empatía afectiva modula la codificación del emoji, pero no la atención temprana y el enganche atencional hacia estos estímulos.

The Influence of Face Inversion and Spatial Frequency on the Self-Positive Expression Processing Advantage

Previous research has examined the impact of late self-evaluation, ignoring the impact of the early visual coding stage and the extraction of facial identity information and expression information on the self-positive expression processing advantage. From the perspective of the processing course, this study examined the stability of the self-positive expression processing advantage and revealed its generation mechanism. In Experiment 1, inverted self-expression and others’ expressive pictures were used to influence early structural coding. In Experiments 2a and 2b, we used expression pictures of high and low spatial frequency, thereby affecting the extraction of facial identity information or expression information in the mid-term stage. The visual search paradigm was adopted in three experiments, asking subjects to respond to the target expression. We found that under the above experimental conditions, the search speed for self-faces was always faster than that for self-angry expressions and others’ faces. These results showed that, compared with others’ expressions and self-angry expressions, self-positive expressions were more prominent and more attractive. These findings suggest that self-expression recognition combines with conceptual self-knowledge to form an abstract and constant processing pattern. Therefore, the processing of self-expression recognition was not affected by the facial orientation and spatial frequencies.

Visual Fixation Assessment in Patients with Disorders of Consciousness Based on Brain-Computer Interface

Visual fixation is an item in the visual function subscale of the Coma Recovery Scale-Revised (CRS-R). Sometimes clinicians using the behavioral scales find it difficult to detect because of the motor impairment in patients with disorders of consciousness (DOCs). Brain-computer interface (BCI) can be used to improve clinical assessment because it directly detects the brain response to an external stimulus in the absence of behavioral expression. In this study, we designed a BCI system to assist the visual fixation assessment of DOC patients. The results from 15 patients indicated that three showed visual fixation in both CRS-R and BCI assessments and one did not show such behavior in the CRS-R assessment but achieved significant online accuracy in the BCI assessment. The results revealed that electroencephalography-based BCI can detect the brain response for visual fixation. Therefore, the proposed BCI may provide a promising method for assisting behavioral assessment using the CRS-R.

Event-related potentials reveal the development of stable face representations from natural variability

Natural variability between instances of unfamiliar faces can make it difficult to reconcile two images as the same person. Yet for familiar faces, effortless recognition occurs even with considerable variability between images. To explore how stable face representations develop, we employed incidental learning in the form of a face sorting task. In each trial, multiple images of two facial identities were sorted into two corresponding piles. Following the sort, participants showed evidence of having learnt the faces performing more accurately on a matching task with seen than with unseen identities. Furthermore, ventral temporal event-related potentials were more negative in the N250 time range for previously seen than for previously unseen identities. These effects appear to demonstrate some degree of abstraction, rather than simple picture learning, as the neurophysiological and behavioural effects were observed with novel images of the previously seen identities. The results provide evidence of the development of facial representations, allowing a window onto natural mechanisms of face learning.

The Effects of Face Inversion and Face Race on the P100 ERP

Research about the neural basis of face recognition has investigated the timing and anatomical substrates of different stages of face processing. Scalp-recorded ERP studies of face processing have focused on the N170, an ERP with a peak latency of ∼170 msec that has long been associated with the initial structural encoding of faces. However, several studies have reported earlier ERP differences related to faces, suggesting that face-specific processes might occur before N170. Here, we examined the influence of face inversion and face race on the timing of face-sensitive scalp-recorded ERPs by examining neural responses to upright and inverted line-drawn and luminance-matched white and black faces in a sample of white participants. We found that the P100 ERP evoked by inverted faces was significantly larger than that evoked by upright faces. Although this inversion effect was statistically significant at 100 msec, the inverted-upright ERP difference peaked at 138 msec, suggesting that it might represent an activity in neural sources that overlap with P100. Inverse modeling of the inversion effect difference waveform suggested possible neural sources in pericalcarine extrastriate visual cortex and lateral occipito-temporal cortex. We also found that the inversion effect difference wave was larger for white faces. These results are consistent with behavioral evidence that individuals process the faces of their own races more configurally than faces of other races. Taken together, the inversion and race effects observed in the current study suggest that configuration influences face processing by at least 100 msec.

Event-Related Potential Responses to Beloved and Familiar Faces in Different Marriage Styles: Evidence from Mosuo Subjects

Research on familiar face recognition has largely focused on the neural correlates of recognizing a beloved partner or family member. However, no research has explored the effect of marriage style on the recognition of a beloved partner's face, especially in matriarchal societies. Here, we examined the time course of event-related potentials (ERP) in response to the face of a beloved partner, sibling, or unknown person in a sample of individuals from the matriarchal Mosuo tribe. Two groups were assessed: intermarriage and walking marriage groups (i.e., couples in a committed relationship who do not cohabitate during the daytime). In agreement with previous reports, ERP results revealed more positive VPP, N250, and P300 waveforms for beloved faces than sibling faces in both groups. Moreover, P300 was more positive for beloved partner versus sibling faces; however, this difference emerged at fronto-central sites for the walking marriage group and at posterior sites for the intermarriage group. Overall, we observed that marriage style affects the later stage processing of a beloved partner's face, and this may be associated with greater affective arousal and familiarity.

Neural correlates of cognitive aging during the perception of facial age: the role of relatively distant and local texture information

Previous event-related potential (ERP) research revealed that older relative to younger adults show reduced inversion effects in the N170 (with more negative amplitudes for inverted than upright faces), suggestive of impairments in face perception. However, as these studies used young to middle-aged faces only, this finding may reflect preferential processing of own- relative to other-age faces rather than age-related decline. We conducted an ERP study in which young and older participants categorized young and old upright or inverted faces by age. Stimuli were presented either unfiltered or low-pass filtered at 30, 20, or 10 cycles per image (CPI). Response times revealed larger inversion effects, with slower responses for inverted faces, for young faces in young participants. Older participants did not show a corresponding effect. ERPs yielded a trend toward reduced N170 inversion effects in older relative to younger adults independent of face age. Moreover, larger inversion effects for young relative to old faces were detected, and filtering resulted in smaller N170 amplitudes. The reduced N170 inversion effect in older adults may reflect age-related changes in neural correlates of face perception. A smaller N170 inversion effect for old faces may indicate that facial changes with age hamper early face perception stages.

Familiar Face Detection in 180 ms

The visual system is tuned for rapid detection of faces, with the fastest choice saccade to a face at 100 ms. Familiar faces have a more robust representation than do unfamiliar faces, and are detected faster in the absence of awareness and with reduced attentional resources. Faces of family and close friends become familiar over a protracted period involving learning the unique visual appearance, including a view-invariant representation, as well as person knowledge. We investigated the effect of personal familiarity on the earliest stages of face processing by using a saccadic-choice task to measure how fast familiar face detection can happen. Subjects made correct and reliable saccades to familiar faces when unfamiliar faces were distractors at 180 ms--very rapid saccades that are 30 to 70 ms earlier than the earliest evoked potential modulated by familiarity. By contrast, accuracy of saccades to unfamiliar faces with familiar faces as distractors did not exceed chance. Saccades to faces with object distractors were even faster (110 to 120 ms) and equivalent for familiar and unfamiliar faces, indicating that familiarity does not affect ultra-rapid saccades. We propose that detectors of diagnostic facial features for familiar faces develop in visual cortices through learning and allow rapid detection that precedes explicit recognition of identity.

Face the hierarchy: ERP and oscillatory brain responses in social rank processing

Recognition of social hierarchy is a key feature that helps us navigate through our complex social environment. Neuroimaging studies have identified brain structures involved in the processing of hierarchical stimuli but the precise temporal dynamics of brain activity associated with such processing remains largely unknown. Here, we used electroencephalography to examine the effect of social hierarchy on neural responses elicited by faces. In contrast to previous studies, the key manipulation was that a hierarchical context was constructed, not by varying facial expressions, but by presenting neutral-expression faces in a game setting. Once the performance-based hierarchy was established, participants were presented with high-rank, middle-rank and low-rank player faces and had to evaluate the rank of each face with respect to their own position. Both event-related potentials and task-related oscillatory activity were investigated. Three main findings emerge from the study. First, the experimental manipulation had no effect on the early N170 component, which may suggest that hierarchy did not modulate the structural encoding of neutral-expression faces. Second, hierarchy significantly modulated the amplitude of the late positive potential (LPP) within a 400-700 ms time-window, with more a prominent LPP occurring when the participants processed the face of the highest-rank player. Third, high-rank faces were associated with the highest reduction of alpha power. Taken together these findings provide novel electrophysiological evidence for enhanced allocation of attentional resource in the presence of high-rank faces. At a broader level, this study brings new insights into the neural processing underlying social categorization.

The role of the eyes in processing an intact face and its scrambled image: a dense array ERP and low-resolution electromagnetic tomography (sLORETA) study

The aim of the present study was to test whether the eyes of an intact face produced a specific brain response compared to the mouth, nose, or hair and whether their specificity was also maintained in a scrambled face. Fifteen subjects were asked to focus visual attention on global and single elements in intact faces and in their scrambled image. EEG data were recorded from 256-Hydrocel Geodesic Sensor-Net200. Event-related potentials (ERPs) analyses showed a difference between the intact face and the scrambled face from N170 component until 600 ms on the occipito-temporal montage and at 400-600 ms on the frontal montage. Only the eyes showed a difference between conditions (intact/scrambled face) at 500 ms. The most activated source detected by sLORETA was the right middle temporal gyrus (BA21) for both conditions and for all elements. Left BA21 resulted in significantly more activation in response to eyes in the intact face compared to the eyes in the scrambled face at 500 ms. The left BA21 has a central role in high-level visual processing and in understanding others' intentions. These findings suggest a specificity of the eyes and indicate that the eyes play the social and communicative role of comprehending the nonverbal intentions of others only when inserted in an intact face.

Behavioral and electrophysiological correlates of intact and scrambled body perception

OBJECTIVE

Intact faces and bodies elicit two prominent electrophysiological components (P100 and N170). The N170 is thought to be related to the structural encoding and configural processing of faces and bodies. The aim of the present study was to investigate whether intact faces and bodies as well as scrambled faces and bodies elicit the same component. This would imply that similar as faces, bodies are encoded as a whole.

METHODS

We used a matching to sample task and two manipulations validated as an assessment of configural processing in previous studies: the inversion effect and intact versus scrambled stimulus presentation.

RESULTS

For both categories, performance was better for intact compared to scrambled stimuli. Additionally, stimulus distortion seems to abolish the body but not the face inversion effect. On the electrophysiological level, we found enhanced N170 amplitudes for intact faces and bodies compared to scrambled stimuli. The opposite pattern engaged in the time-window of the P100. Furthermore, for the N170 we observed an inversion effect for intact but not scrambled bodies.

CONCLUSIONS

First-order relational information are important for the perception of bodies and might be processed in the N170 time-window. Disrupting this information interacts with the inversion effect.

SIGNIFICANCE

The current data suggest that faces and bodies might be processed by distinct mechanisms as the experimental manipulation affected faces in a different way than bodies.

Electrophysiological responses in mothers to their own and unfamiliar child's gaze information

An attachment bond between a mother and her child is one of the most intimate human relationships. It is important for a mother to be sensitive to her child's gaze direction because exchanging gaze information plays a vital role in their relationship. Furthermore, recent studies have revealed differential neural activation patterns in mothers when presented the faces of their own children or the unfamiliar child of other people. Based on these findings, in the present study, we investigated whether mothers show differential neural responses to gaze information of their own child compared to that of an unfamiliar child. To this end, event-related-potentials elicited by the faces of one's own or an unfamiliar child with straight or averted gaze directions were measured using an oddball-paradigm. The results showed that peak amplitudes of the N170 component were enlarged by viewing the straight gazes compared to the averted gazes of one's own child, but not of an unfamiliar child. When the gaze was directed straight, the P3 amplitude elicited by one's own child's face is smaller than that elicited by an unfamiliar child's face. P3s elicited in viewing one's own child's face with averted gaze and in viewing an unfamiliar child's face with straight gaze were positively correlated with state-anxiety. These results bolster the hypothesis that processing the gaze information of one's own child elicits differential neural activation compared to the gaze information of an other person's unfamiliar child at both perceptual and evaluative stages of face processing.

"Wanted!" the effects of reward on face recognition: electrophysiological correlates

The aim of the present study was to uncover the temporal dynamics of face recognition as a function of reward. Event-related potentials (ERPs) were recorded during the encoding and the subsequent old/new memory test in response to faces that could be associated with a monetary reward. The behavioral results showed that faces associated with reward at both encoding and retrieval were recognized better than the unrewarded ones. ERP responses highlighted that successful encoding predictive of subsequent memory was greater for faces associated with reward than for faces without reward-driven motivational learning. At retrieval, an early positive-going component was elicited for potentially rewarded faces on frontal regions, while the occipito-temporal N170 component showed priming effects as a function of reward. Later on, larger centro-parietal ERP components, related to recognition memory, were found selectively for reward-associated faces. Remarkably, electrophysiological responses varied in a graded manner, with the largest amplitude yielded by faces with double reward, followed by faces associated with reward only at encoding. Taken together, the present data show that the processing of outcome expectations affects face structural encoding and increases memory efficiency, yielding a robust and sustained modulation over frontal and temporal areas where reward and memory mechanisms operate in conjunction.

Mirror, mirror on the wall, how does my brain recognize my image at all?

For decades researchers have used mirrors to study self-recognition. However, attempts to identify neural processes underlying this ability have used photographs instead. Here we used event related potentials (ERPs) to compare self-face recognition in photographs versus mirrors and found distinct neural signatures. Measures of visual self-recognition are therefore not independent of the medium employed.