Electrophysiological correlates of the composite face illusion: Disentangling perceptual and decisional components of holistic face processing in the human brain

When the bottom halves of two faces differ, people’s behavioral judgment of the identical top halves of those faces is impaired: they report that the top halves are different, and/or take more time than usual to provide a response. This behavioral measure is known as the composite face effect (CFE) and has traditionally been taken as evidence that faces are perceived holistically. Recently, however, it has been claimed that this effect is driven almost entirely by decisional, rather than perceptual, factors ( Richler, Gauthier, Wenger, & Palmeri, 2008). To disentangle the contribution of perceptual and decisional brain processes, we aimed to obtain an event-related potential (ERP) measure of the CFE at a stage of face encoding ( Jacques & Rossion, 2009) in the absence of a behavioral CFE effect. Sixteen participants performed a go/no-go task in an oddball paradigm, lifting a finger of their right or left hand when the top half of a face changed identity. This change of identity of the top of the face was associated with an increased ERP signal on occipito-temporal electrode sites at the N170 face-sensitive component (∼160 ms), the later decisional P3b component, and the lateralized readiness potential (LRP) starting at ∼350 ms. The N170 effect was observed equally early when only the unattended bottom part of the face changed, indicating that an identity change was perceived across the whole face in this condition. Importantly, there was no behavioral response bias for the bottom change trials, and no evidence of decisional biases from electrophysiological data (no P3b and LRP deflection in no-go trials). These data show that an early CFE can be measured in ERPs in the absence of any decisional response bias, indicating that the CFE reflects primarily the visual perception of the whole face.     

Normal perception of Mooney faces in developmental prosopagnosia: Evidence from the N170 component and rapid neural adaptation

Individuals with developmental prosopagnosia (DP) have a severe difficulty recognizing the faces of known individuals in the absence of any history of neurological damage. These recognition problems may be linked to selective deficits in the holistic/configural processing of faces. We used two‐tone Mooney images to study the processing of faces versus non‐face objects in DP when it is based on holistic information (or the facial gestalt) in the absence of obvious local cues about facial features. A rapid adaptation procedure was employed for a group of 16 DPs. Naturalistic photographs of upright faces were preceded by upright or inverted Mooney faces or by Mooney houses. DPs showed face‐sensitive N170 components in response to Mooney faces versus houses, and N170 amplitude reductions for inverted as compared to upright Mooney faces. They also showed the typical pattern of N170 adaptation effects, with reduced N170 components when upright naturalistic test faces were preceded by upright Mooney faces, demonstrating that the perception of Mooney and naturalistic faces recruits shared neural populations. Our findings demonstrate that individuals with DP can utilize global information about face configurations for categorical discriminations between faces and non‐face objects, and suggest that face processing deficits emerge primarily at more fine‐grained higher level stages of face perception.     

Holistic face perception: Mind the gap!

The most widely used measurement of holistic face perception, the composite face effect (CFE), is challenged by two apparently contradictory goals: having a defined face part (i.e., the top half), and yet perceiving the face as an integrated unit (i.e., holistically). Here, we investigated the impact of a small gap between top and bottom face halves in the standard composite face paradigm, requiring matching of sequentially presented top face halves. In Experiment 1, the CFE was larger for no-gap than gap stimuli overall, but not for participants who were presented with gap stimuli first, suggesting that the area of the top face half was unknown without a gap. This was confirmed in Experiment 2, in which these two stimulus sets were mixed up: the gap stimuli thus provided information about the area of a top face half and the magnitude of the CFE did not differ between stimulus sets. These observations indicate that the CFE might be artificially inflated in the absence of a stimulus cue that objectively defines a border between the face halves. Finally, in Experiment 3, observers were asked to determine which of two simultaneously presented faces was the composite face. Perceptual judgements for no-gap stimuli approached ceiling; however, with a gap, participants were almost unable to distinguish the composite face from a veridical face. This effect was not only due to low-level segmentation cues at the border of no-gap face halves, because stimulus inversion decreased performance in both conditions. This result indicates that the two halves of different faces may be integrated more naturally with a small gap that eliminates an enhanced contrast border. Collectively, these observations suggest that a small gap between face halves provides an objective definition of the face half to match and is beneficial for valid measurement of the behavioural CFE.     

Electrophysiological correlates of face distortion after-effects

When observers are exposed to a distorted face the perceived configuration of a subsequently presented face is altered, a phenomenon called face distortion after-effect (FDAE). We compared the face-related components of the event-related potential (ERP) after adaptation to noise images—veridical and distorted faces. We found large bilateral adaptation effects on the P100 and N170 components that are related to face detection. Moreover, we found smaller adaptation effects on the N170, recorded over the right hemisphere, which can be related to the behavioural distortion after-effect and to face configurations. Our results suggest that the observed ERP adaptation effects are general for various steps of face processing and that the FDAEs similarly to gender after-effects are related to the early face-specific ERP components.     

Development of a view-invariant representation of the human head

Do infants perceive visual cues as diverse as frontal-view faces, profiles or bodies as being different aspects of the same object, a fellow human? If that is the case, visual exposure to one such cue should facilitate the subsequent processing of the others. To verify this hypothesis, we recorded event-related responses in 4-month-old infants and in adults. Pictures of eyes were interleaved amongst images belonging to three human contexts (frontal-view faces, profiles or bodies) or non-human contexts (houses, cars or pliers). In adults, both profile and frontal-face contexts elicited suppression of the N170 response to eye pictures, indicating an access to a view-invariant representation of faces. In infants, a response suppression of the N290 component was recorded only in the context of frontal faces, while profile context induces a different effect (i.e., a P400 enhancement) on eye processing. This dissociation suggests that the view-invariant representation of faces is learned, as it is for other 3-D objects and needs more than 4 months of exposure to be established. In a follow-up study, where infants were exposed to a short movie showing people rotating their heads, the profile-induced P400 effect was speeded up, indicating that exposure to successive views of the same object is probably a way to build up adult-like face representations.     

Maternal odor shapes rapid face categorization in the infant brain

To successfully interact with a rich and ambiguous visual environment, the human brain learns to differentiate visual stimuli and to produce the same response to subsets of these stimuli despite their physical difference. Although this visual categorization function is traditionally investigated from a unisensory perspective, its early development is inherently constrained by multisensory inputs. In particular, an early‐maturing sensory system such as olfaction is ideally suited to support the immature visual system in infancy by providing stability and familiarity to a rapidly changing visual environment. Here, we test the hypothesis that rapid visual categorization of salient visual signals for the young infant brain, human faces, is shaped by another highly relevant human‐related input from the olfactory system, the mother's body odor. We observe that a right‐hemispheric neural signature of single‐glance face categorization from natural images is significantly enhanced in the maternal versus a control odor context in individual 4‐month‐old infant brains. A lack of difference between odor conditions for the common brain response elicited by both face and non‐face images rules out a mere enhancement of arousal or visual attention in the maternal odor context. These observations show that face‐selective neural activity in infancy is mediated by the presence of a (maternal) body odor, providing strong support for multisensory inputs driving category acquisition in the developing human brain and having important implications for our understanding of human perceptual development.     

羞怯与非羞怯大学生在早期面孔加工中的差异——来自ERP的电生理学证据

羞怯与社会认知密切相关,而面孔识别是人们社会生活中的一项重要的社会认知功能。目前关于羞怯的电生理学研究大多关注表情的效价效应和面孔的新旧效应对羞怯个体面孔加工的影响,却忽视了羞怯个体在基本的面孔识别能力——面孔-物体识别中可能存在的认知神经差异。因此,本研究采用ERP技术,使用GO/Nogo范式的面孔-物体识别任务,对17名羞怯大学生和17名非羞怯大学生在面孔结构编码中的N170成分进行考察,以期发现不同羞怯水平大学生在早期面孔加工中的认知神经差异。本研究发现,非羞怯大学生对面孔结构具有加工优势,识别面孔时,非羞怯大学生的N170波幅显著大于羞怯大学生的N170波幅,识别物体时则不存在组间差异;N170是面孔识别的特异性成分,面孔诱发的N170波幅显著大于物体诱发的N170波幅;识别面孔时,N170表现出大脑右半球的加工优势。     

卡通面孔分类与识别加工的ERP比较研究

通过ERP方法,考察卡通面孔分类（人和动物）的脑机制及其与卡通面孔识别（人与车）的差异。结果表明,分类任务中,动物面孔VPP潜伏期显著长于人,N170潜伏期主效应不显著、波幅半球效应显著,LPP波幅在顶叶和中央区最大;分类任务VPP和LPP波幅均显著大于识别。结论：卡通面孔分类比识别速度慢、强度大,消耗心理资源多。顶叶和中央区可能是执行分类任务的主要脑区,且加工人类面孔具有优势。面孔加工中结构编码和特征编码可能部分是并行的。     

The electrophysiology of introspection

To study whether the distinction between introspective and non-introspective states of mind is an empirical reality or merely a conceptual distinction, we measured event-related potentials (ERPs) elicited in introspective and non-introspective instruction conditions while the observers were trying to detect the presence of a masked stimulus. The ERPs indicated measurable differences related to introspection in both preconscious and conscious processes. Our data support the hypothesis that introspective states empirically differ from non-introspective states.     

人类面孔识别工作记忆的脑电位特征

采用事件相关电位(ERPs)技术探索延迟匹配任务范式下面孔识别工作记忆的脑电位特征。实验以面孔图片为刺激,在校大学生被试完成靶匹配工作记忆任务。结果发现,被试识别靶面孔及分心物面孔时均在枕颞区两侧诱发N170,且靶与分心物的N170振幅在相同电极上都没有显著差异,在颞区两侧的P7和P8上差异显著;无论靶面孔还是分心物面孔,工作记忆的 ERPs均产生了 P300成分。在分别追踪新靶和熟悉靶的工作记忆任务条件下,靶与分心物的ERPs波形在250 ms后出现分离,且靶刺激波幅均比分心物更正,新靶比熟悉靶更正。熟悉分心物与新分心物之间显示出250~650 ms的前额区旧/新效应,在晚期的450~650 ms时段,新工作记忆比旧工作记忆波幅更正。这些结果表明,面孔识别的N170效应可能反映的是面孔知觉的整体加工,且 N170的右半球优势具体为颞区的右侧优势;先前的面孔学习会影响工作记忆期间大脑对面孔的识别反应。     

情绪概念加工与情绪面孔知觉的相互影响

通过3个实验探讨情绪概念加工与情绪面孔知觉是否存在相互影响, 以及加工深度对两者关系的影响。实验1采用情绪面孔启动范式, 探讨较深的情绪概念加工层面对情绪概念与情绪面孔的关系的影响。实验2更改概念任务, 探讨较浅的概念加工层面对两者关系的影响。实验3缩短启动面孔呈现时间, 探讨较浅的面孔知觉层面对两者关系的影响。通过研究主要得出以下结论：(1)情绪概念加工与情绪面孔知觉确实存在相互影响; (2)概念加工深度影响两者关系的方向性, 在较深的概念加工层面, 两者的关系是双向的, 在较浅的概念加工层面, 两者的关系是单向的; (3)知觉加工深度也影响两者关系的方向性, 在较深的知觉加工层面, 两者的关系是双向的, 在较浅的知觉加工层面, 没有发现两者的相互影响。本研究为抽象概念的具身表征提供了实证支持。     

The role of holistic face processing in acquired prosopagnosia: evidence from the composite face effect

Faces are processed more holistically than other objects, and it has been suggested that the loss of holistic face processing causes acquired prosopagnosia. Support for this hypothesis comes from several cases who failed to show holistic face effects as well as the absence of reports of prosopagnosics with unequivocally normal holistic face perception. The current study examines the relationship between holistic face processing and prosopagnosia by testing seven acquired prosopagnosics with the face composite task, a classic measure of holistic face processing. To enhance the robustness of the findings, each prosopagnosic was tested with two versions of the composite task showing upright faces. We also tested an inverted condition to exclude the possibility that more general factors account for composite effects for upright faces. Four of the seven acquired prosopagnosic participants showed consistent upright face composite effects with minimal inverted face composite effects. We conclude that severe face processing deficits can co-occur with intact holistic face processing and that factors other than a loss of holistic processing contribute to the perceptual and recognition deficits in acquired prosopagnosia.     

面孔倒置效应的研究与理论述评

面孔倒置效应是指, 个体对倒置面孔的再认成绩显著低于对正立面孔的再认成绩, 而且, 与普通物体的倒置效应相比, 面孔的倒置效应更大。研究者们针对面孔倒置效应提出了多种理论假说, 两种主要的理论解释是：第一, 倒置面孔破坏了面孔的结构特征, 影响了面孔的整体加工, 所以, 个体对倒置面孔的再认成绩较差; 第二, 眼睛在面孔加工中起重要作用, 尤其在倒置面孔中的作用更明显, 使得倒置面孔N170波幅较高。ERP和fMRI研究提示, 未来研究需要进一步明确眼睛、注意等在面孔倒置效应中的作用。     

Levels of representation in the electrophysiology of speech perception

Mapping from acoustic signals to lexical representations is a complex process mediated by a number of different levels of representation. This paper reviews properties of the phonetic and phonological levels, and hypotheses about how category structure is represented at each of these levels, and evaluates these hypotheses in light of relevant electrophysiological studies of phonetics and phonology. The paper examines evidence for two alternative views of how infant phonetic representations develop into adult representations, a structure-changing view and a structure-adding view, and suggests that each may be better suited to different kinds of phonetic categories. Electrophysiological results are beginning to provide information about phonological representations, but less is known about how the more abstract representations at this level could be coded in the brain.     

ERP evidence for task modulations on face perceptual processing at different spatial scales

Does the perceptual processing of faces flexibly adapt to the requirements of the categorization task at hand, or does it operate independently of this cognitive context? Behavioral studies have shown that the fine and coarse spatial scales of a face are differentially processed depending on the categorization task performed, thus suggesting that the latter can influence stimulus perception. Here, we investigated the time course of these task influences on perceptual processing by examining the visual N170 face‐sensitive Event‐Related Potential (ERP), while observers categorized faces for their gender and familiarity. Stimuli were full spectrum, or filtered versions that preserved either coarse or fine scale information of the faces. Behavioral results replicated previous findings of a differential processing of coarse and fine spatial scales across tasks. In addition, the N170 amplitude was larger in the Gender task as compared to the Familiarity task for LSF faces exclusively, thus showing that task demands differentially modulated the spatial scale processing on faces. These results suggest that the diagnosticity of scale‐specific cues in categorization tasks can modulate face processing.     

Dissociation between the behavioural and electrophysiological effects of the face and body composite illusions

Several studies have reported similarities between perceptual processes underlying face and body perception, particularly emphasizing the importance of configural processes. Differences between the perception of faces and the perception of bodies were observed by means of a manipulation targeting a specific subtype of configural processing: the composite illusion. The composite face illusion describes the fact that two identical top halves of a face are perceived as being different if they are presented with different bottom parts. This effect disappears, if both halves are laterally shifted. Crucially, the effect of misalignment is not observed for bodies. This study aimed to further explore differences in the time course of face and body perception by using the composite effect. The present results replicated behavioural effects illustrating that misalignment affects the perception of faces but not bodies. Thus, face but not body perception relies on holistic processing. However, differences in the time course of the processing of both stimulus categories emerged at the N170 and P200. The pattern of the behavioural data seemed to be related to the P200. Thus, the present data indicate that holistic processes associated with the effect of misalignment might occur 200 ms after stimulus onset.     

Carryover of scanning behaviour affects upright face recognition differently to inverted face recognition

Face perception is characterized by a distinct scanpath. While eye movements are considered functional, there has not been direct evidence that disrupting this scanpath affects face recognition performance. The present experiment investigated the influence of an irrelevant letter-search task (with letter strings arranged horizontally, vertically, or randomly) on the subsequent scanning strategies in processing upright and inverted famous faces. Participants’ response time to identify the face and the direction of their eye movements were recorded. The orientation of the letter search influenced saccadic direction when viewing the face images, such that a direct carryover-effect was observed. Following a vertically oriented letter-search task, the recognition of famous faces was slower and less accurate for upright faces, and faster for inverted faces. These results extend the carryover findings of Thompson and Crundall into a novel domain. Crucially they also indicate that upright and inverted faces are better processed by different eye movements, highlighting the importance of scanpaths in face recognition.     

The role of the mother's voice in developing mother's face preference: Evidence for intermodal perception at birth

Four experiments are described which investigated the role of the mother's voice in facilitating recognition of the mother's face at birth. Experiment 1 replicated our previous findings (Br. J. Dev. Psychol. 1989; 7: 3–15; The origins of human face perception by very young infants. Ph.D. Thesis, University of Glasgow, Scotland, UK, 1990) indicating a preference for the mother's face when a control for the mother's voice and odours was used only during the testing. A second experiment adopted the same procedures, but controlled for the mother's voice from birth through testing. The neonates were at no time exposed to their mother's voice. Under these conditions, no preference was found. Further, neonates showed only few head turns towards both the mother and the stranger during the testing. Experiment 3 looked at the number of head turns under conditions where the newborn infants were exposed to both the mother's voice and face from birth to 5 to 15 min prior to testing. Again, a strong preference for the mother's face was demonstrated. Such preference, however, vanished in Experiment 4, when neonates had no previous exposure to the mother's voice–face combination. The conclusion drawn is that a prior experience with both the mother's voice and face is necessary for the development of face recognition, and that intermodal perception is evident at birth. The neonates' ability to recognize the face of the mother is most likely to be rooted in prenatal learning of the mother's voice. Copyright © 2004 John Wiley & Sons, Ltd.     

Does silent reading speed in normal adult readers depend on early visual processes? evidence from event-related brain potentials

Little is known about the relationship of reading speed and early visual processes in normal readers. Here we examined the association of the early P1, N170 and late N1 component in visual event-related potentials (ERPs) with silent reading speed and a number of additional cognitive skills in a sample of 52 adult German readers utilizing a Lexical Decision Task (LDT) and a Face Decision Task (FDT). Amplitudes of the N170 component in the LDT but, interestingly, also in the FDT correlated with behavioral tests measuring silent reading speed. We suggest that reading speed performance can be at least partially accounted for by the extraction of essential structural information from visual stimuli, consisting of a domain-general and a domain-specific expertise-based portion.     

The electrophysiological correlates of integrated face and body-part perception

Previous studies have suggested that the human visual system processes faces and bodies holistically—that is, the different body parts are integrated into a unified representation. However, the time course of this integrative process is less known. In the present study, we investigated this issue by recording event-related potentials evoked by a face and two hands presented simultaneously and in different configurations. When the hands were rotated to obtain a biologically implausible configuration, a reduction of the P2 amplitude was observed relative to the condition in which the face and hands were retained in their veridical configuration and were supplemented with visual cues to highlight further the overall body posture. Our results show that the P2 component is sensitive to manipulations affecting the configuration of face and hand stimuli and suggest that the P2 reflects the operation of perceptual mechanisms responsible for the integrated processing of visually presented body parts.