Activation of preexisting and acquired face representations: the N250 event-related potential as an index of face familiarity

Electrophysiological studies using event-related potentials have demonstrated that face stimuli elicit a greater negative brain potential in right posterior recording sites 170 msec after stimulus onset (N170) relative to nonface stimuli. Results from repetition priming paradigms have shown that repeated exposures of familiar faces elicit a larger negative brainwave (N250r) at inferior temporal sites compared to repetitions of unfamiliar faces. However, less is known about the time course and learning conditions under which the N250 face representation is acquired. In the familiarization phase of the Joe/no Joe task, subjects studied a target "Joe" face ("Jane" for female subjects) and, during the course of the experiment, identified a series of sequentially presented faces as either Joe or not Joe. The critical stimulus conditions included the subject's own face, a same-sex Joe ( Jane) face and a same-sex "other" face. The main finding was that the subject's own face produced a focal negative deflection (N250) in posterior channels relative to nontarget faces. The task-relevant Joe target face was not differentiated from other nontarget faces in the first half of the experiment. However, in the second half, the Joe face produced an N250 response that was similar in magnitude to the own face. These findings suggest that the N250 indexes two types of face memories: a preexperimentally familiar face representation (i.e., the "own face" and a newly acquired face representation (i.e., the Joe/Jane face) that was formed during the course of the experiment.     

Event-related brain potentials distinguish processing stages involved in face perception and recognition.

OBJECTIVES: An event-related brain potential (ERP) study investigated how different processing stages involved in face identification are reflected by ERP modulations, and how stimulus repetitions and attentional set influence such effects.METHODS: ERPs were recorded in response to 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.RESULTS: The face-specific N170 component elicited maximally at lateral temporal electrodes was not affected by face familiarity. When compared with unfamiliar faces, familiar faces elicited an enhanced negativity between 300 and 500 ms ('N400f') which was followed by an enhanced positivity beyond 500 ms post-stimulus ('P600f'). In contrast to the 'classical' N400, these effects were parietocentrally distributed. They were attenuated, but still reliable, for repeated presentations of familiar faces. When attention was directed to another demanding task, no 'N400f' was elicited, but the 'P600f' effect remained to be present.CONCLUSIONS: While the N170 reflects the pre-categorical structural encoding of faces, the 'N400f' and 'P600f' are likely to indicate subsequent processes involved in face recognition. Impaired structural encoding can result in the disruption of face identification. This is illustrated by a neuropsychological case study, demonstrating the absence of the N170 and later ERP indicators of face recognition in a prosopagnosic patient.     

Face versus non-face object perception and the 'other-race' effect: a spatio-temporal event-related potential study.

OBJECTIVE: To investigate a modulation of the N170 face-sensitive component related to the perception of other-race (OR) and same-race (SR) faces, as well as differences in face and non-face object processing, by combining different methods of event-related potential (ERP) signal analysis. METHODS: Sixty-two channel ERPs were recorded in 12 Caucasian subjects presented with Caucasian and Asian faces along with non-face objects. Surface data were submitted to classical waveforms and ERP map topography analysis. Underlying brain sources were estimated with two inverse solutions (BESA and LORETA). RESULTS: The N170 face component was identical for both race faces. This component and its topography revealed a face specific pattern regardless of race. However, in this time period OR faces evoked significantly stronger medial occipital activity than SR faces. Moreover, in terms of maps, at around 170 ms face-specific activity significantly preceded non-face object activity by 25 ms. These ERP maps were followed by similar activation patterns across conditions around 190-300 ms, most likely reflecting the activation of visually derived semantic information. CONCLUSIONS: The N170 was not sensitive to the race of the faces. However, a possible pre-attentive process associated to the relatively stronger unfamiliarity for OR faces was found in medial occipital area. Moreover, our data provide further information on the time-course of face and non-face object processing.     

Is the N170 for faces cognitively penetrable? Evidence from repetition priming of Mooney faces of familiar and unfamiliar persons

Impoverished images of faces, two-tone Mooney faces, severely impair the ability to recognize to whom the face pertains. However, previously seeing the corresponding face in a clear format helps fame-judgments to Mooney faces. In the present experiment, we sought to demonstrate that enhancement in the perceptual encoding of Mooney faces results from top-down effects, due to previous activation of familiar face representation. Event-related potentials (ERPs) were obtained for target Mooney images of familiar and unfamiliar faces preceded by clear pictures portraying either the same photo (same photo prime), or a different photo of the same person (different photo prime) or a new unfamiliar face (no-prime). In agreement with previous findings the use of primes was effective in enhancing the recognition of familiar faces in Mooney images; this priming effect was larger in the same than in different photo priming condition. ERP data revealed that the amplitude of the N170 face-sensitive component was smaller when elicited by familiar than by unfamiliar face targets, and for familiar face targets primed by the same than by different photos (a graded priming effect). Because the priming effect was restricted to familiar faces and occurred at the peak of the N170, we suggest that the early perceptual stage of face processing is likely to be penetrable by the top-down effect due to the activation of face representations within the face recognition system.     

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.     

Working memory load for faces modulates P300, N170, and N250r

We used event-related potential (ERP) methodology to examine neural activity associated with visual working memory (WM) for faces. There were two main goals. First, to extend previous findings of P300 load modulation to WM for faces. Second, to examine whether N170 and N250r are also influenced by WM load. Between one and four unfamiliar faces were simultaneously presented for memory encoding. After a 1-sec delay, a target face appeared, and participants had to judge whether this face was part of the previous face array. P300 amplitude decreased as WM load increased, and this P300 suppression was observed at both encoding and retrieval. WM load was also found to modulate other ERPs. The amplitude of the N170 elicited by the target face decreased with load, and this N170 decrease leveled off at load 2, reflecting the behavioral WM capacity of around two faces. In addition, the N250r, observed as an ERP difference for target faces that were present in the encoding array relative to target faces that were absent, was also reduced for higher WM loads. These findings extend previous work by showing that P300 modulation by WM load also occurs for faces. Furthermore, we show, for the first time, that WM load affects the N250r and the early visual N170 component. This suggests that higher visual areas play an important role in WM for faces.     

ERPs associated with familiarity and degree of familiarity during face recognition

Event-related potentials (ERPs) triggered by three different faces (unfamiliar, famous, and the subject's own) were analyzed during passive viewing. A familiarity effect was defined as a significant difference between the two familiar faces as opposed to the unfamiliar face. A degree of familiarity effect was defined as a significant difference between all three conditions. The results show a familiarity effect 170 ms after stimulus onset (N170), with larger amplitudes seen for both familiar faces. Conversely, a degree of familiarity effect arose approximately 250 ms after stimulus onset (P2) in the form of progressively smaller amplitudes as a function of familiarity (subject's face < famous face < unfamiliar). These results demonstrate that the structural encoding of faces, as reflected by N170 activities, can be modulated by familiarity and that facial representations acquire specific properties as a result of experience. Moreover, these results confirm the hypothesis that N170 is sensitive to face versus, object discriminations and to the discrimination among faces.     

Effects of anticaricaturing vs. caricaturing and their neural correlates elucidate a role of shape for face learning

To assess the role of shape information for unfamiliar face learning, we investigated effects of photorealistic spatial anticaricaturing and caricaturing on later face recognition. We assessed behavioural performance and event-related brain potential (ERP) correlates of recognition, using different images of anticaricatures, veridical faces, or caricatures at learning and test. Relative to veridical faces, recognition performance improved for caricatures, with performance decrements for anticaricatures in response times. During learning, an amplitude pattern with caricatures>veridicals=anticaricatures was seen for N170, left-hemispheric ERP negativity during the P200 and N250 time segments (200-380ms), and for a late positive component (LPC, 430-830ms), whereas P200 and N250 responses exhibited an additional difference between veridicals and anticaricatures over the right hemisphere. During recognition, larger amplitudes for caricatures again started in the N170, whereas the P200 and the right-hemispheric N250 exhibited a more graded pattern of amplitude effects (caricatures>veridicals>anticaricatures), a result which was specific to learned but not novel faces in the N250. Together, the results (i) emphasise the role of facial shape for visual encoding in the learning of previously unfamiliar faces and (ii) provide important information about the neuronal timing of the encoding advantage enjoyed by faces with distinctive shape.     

Prosopagnosia and structural encoding of faces: evidence from event-related potentials

Event-related brain potentials (ERPs) were recorded in response to unfamiliar faces and to houses from a severely prosopagnosic patient (PHD) and 24 control subjects. For all control subjects, faces elicited an enhanced negativity at lateral temporal electrodes (N170). This component was absent for PHD. Comparable results were obtained in response to inverted faces and houses. A selective deficit in face recognition is therefore reflected by abnormalities in ERP components specific to faces. As PHD was shown to have substantial deficits on tasks requiring the structural analysis of faces, these findings are consistent with the view that the N170 reflects processes involved in the structural encoding of faces, and may be a measure of selective impairments in the analysis of face components.     

Human brain potential correlates of repetition priming in face and name recognition

We investigated repetition priming in the recognition of famous people by recording event-related brain potentials (ERPs) and reaction times (RTs). Participants performed speeded two-choice responses depending on whether or not a stimulus showed a famous person. In Experiment 1, a facilitation was found in RTs to famous (but not to unfamiliar) faces when primed by the same face shown in an earlier priming phase of the experiment. In ERPs, an influence of repetition priming was observed neither for the N170 nor for a temporal N250 component which in previous studies had been shown to be sensitive to immediate face repetitions. ERPs to primed unfamiliar faces were more negative over right occipitotemporal areas than those to unprimed faces, but this effect was specific for repetitions of the same image, consistent with recent findings. In contrast, ERPs to primed familiar faces were more positive than those to unprimed faces at parietal sites from 500-600 ms after face onset, and these priming effects were comparable regardless of whether the same or a different image of the celebrity had served as prime. In Experiment 2, similar results were found for name recognition-a facilitation in RTs to primed familiar but not unfamiliar names, and a parietal positivity to primed names around 500-600 ms. ERP repetition effects showed comparable topographies for faces and names, consistent with the idea of a common underlying source. With reference to current models of face recognition, we suggest that these ERP repetition effects for familiar stimuli reflect a change in post-perceptual representations for people, rather than a neural correlate of recognition at a perceptual level.     

ERPs ASSOCIATED WITH FAMILIARITY AND DEGREE OF FAMILIARITY DURING FACE RECOGNITION

Event-related potentials (ERPs) triggered by three different faces (unfamiliar, famous, and the subject's own) were analyzed during passive viewing. A familiarity effect was defined as a significant difference between the two familiar faces as opposed to the unfamiliar face. A degree of familiarity effect was defined as a significant difference between all three conditions. The results show a familiarity effect 170 ms after stimulus onset (NI70), with larger amplitudes seen for both familiar faces. Conversely, a degree of familiarity effect arose approximately 250 ms after stimulus onset (P2) in the form of progressively smaller amplitudes as a function of familiarity (subject s face < famous face < unfamiliar). These results demonstrate that the structural encoding of faces, as reflected by N170 activities, can be modulated by familiarity and that facial representations acquire specific properties as a result of experience. Moreover, these results confirm the hypothesis that N170 is sensitive to face versus. object discriminations and to the discrimination among faces.     

Exploring the functional architecture of person recognition system with event-related potentials in a within- and cross-domain self-priming of faces

In this paper, we explored the functional properties of person recognition system by investigating the onset, magnitude, and scalp distribution of within- and cross-domain self-priming effects on event-related potentials (ERPs). Recognition of degraded pictures of famous people was enhanced by a prior exposure to the same person's face (within-domain self-priming) or name (cross-domain self-priming) as compared to those preceded by neutral or unrelated primes. The ERP results showed first that the amplitude of the N170 component to famous face targets was modulated by within- and cross-domain self-priming, suggesting not only that the N170 component can be affected by top–down influences but also that this top–down effect crosses domains. Second, similar to our behavioral data, later ERPs to famous faces showed larger ERP self-priming effects in the within-domain than in the cross-domain condition. In addition, the present data dissociated between two topographically and temporally overlapping priming-sensitive ERP components: the first one, with a strongly posterior distribution arising at an early onset, was modulated more by within-domain priming irrespective whether the repeated face was familiar or not. The second component, with a relatively uniform scalp distribution, was modulated by within- and cross-domain priming of familiar faces. Moreover, there was no evidence for ERP-induced modulations for unfamiliar face targets in the cross-domain condition. Together, our findings suggest that multiple neurocognitive events that are possibly mediated by distinct brain loci contribute to face priming effects.     

Early adaptation to repeated unfamiliar faces across viewpoint changes in the right hemisphere: Evidence from the N170 ERP component

Event-related potential (ERP) studies have shown that sensitivity to individual faces emerges as early as ∼160 ms in the human occipitotemporal cortex (N170). Here we tested whether this effect generalizes across changes in viewpoint. We recorded ERPs during an unfamiliar individual face adaptation paradigm. Participants were presented first with an adapting face (∼3000 ms) rotated 30° in depth, followed by a second face (200 ms) in a frontal view of either the same or a different identity. The N170 amplitude at right occipitotemporal sites to the second stimulus was reduced for repeated as compared to different faces. A bilateral adaptation effect emerged after 250 ms following stimulus onset. These observations indicate that individual face representations activated as early as 160 ms after stimulus onset in the right hemisphere show a substantial degree of generalization across viewpoints.     

Putting a name to a face: the role of name labels in the formation of face memories

Although previous research in ERPs has focused on the conditions under which faces are recognized, less research has focused on the process by which face representations are acquired and maintained. In Experiment 1, participants were required to monitor for a target "Joe" face that was shown among a series of nontarget "Other" faces. At the halfway point, participants were instructed to switch targets from the Joe face to a previous nontarget face that is now labeled "Bob." The ERP analysis focused on the posterior N250 component known to index face familiarity and the P300 component associated with context updating and response decision. Results showed that, in the first half of the experiment, there was increase in N250 negativity to the target Joe face compared with the nontarget Bob and designated Other face. In the second half of the experiment, an enhanced N250 negativity was produced to the now-target Bob face compared with the Other face. Critically, the enhanced N250 negativity to the Joe face was maintained, although Joe was no longer the target. The P300 component followed a similar pattern of brain response, where the Joe face elicited a significantly larger P300 amplitude than the Other face and the Bob face. In the Bob half of the experiment, the Bob face elicited a reliably larger P300 than the Other faces, and the heightened P300 to the Joe face was sustained. In Experiment 2, we examined whether the increased N250 and P300 to Joe was because of simple naming effects. Participants were introduced to both Joe and Bob faces and names at the beginning of the experiment. In the first half of the experiment, participants monitored for the target Joe face and at the halfway point, they were instructed to switch targets to the Bob face. Findings show that N250 negativity significantly increased to the Joe face relative to the Bob and Other faces in the first half of the experiment and an enhanced N250 negativity was found for the target Bob face and the nontarget Joe face in the second half. An increased P300 amplitude was demonstrated to the target Joe and Bob faces in the first and second halves of the experiment, respectively. Importantly, the P300 amplitude elicited by the Joe face equaled the P300 amplitude to the Bob face, although it was no longer the target face. The findings from Experiments 1 and 2 suggest that the N250 component is not solely determined by name labeling, exposure, or task relevancy, but it is the combination of these factors that contribute to the acquisition of enduring face representations.     

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.     

Recognition memory for unfamiliar faces in Parkinson's disease: behavioral and electrophysiologic measures

We analyzed event-related potentials (ERPs) and behavioral measurements during a recognition memory task in 15 normal elderly subjects and 15 patients with Parkinson's disease (PD). To elicit ERPs unfamiliar faces were repeated immediately after initial presentation (at lag 0), after one intervening face (at lag 1) or at lag 3. Compared to normal controls, PD patients showed decreased accuracy in recognizing new unfamiliar faces. P170 latency and amplitude were similar between both groups. ERP amplitude between 300 and 500 ms after the stimulus in control subjects showed a positive shift (ERP repetition effect) for lag 0 at all sites and for lag 1 and 3 repetitions at the Fz site, while effects in the PD group were not noted at any site, even for the lag 0 repetition. ERP waveforms for the first presentation of faces in PD patients showed a significant positive shift compared to normal controls. These data suggest intact perception but impaired recognition memory for unfamiliar faces in PD. In addition, recognition memory deficits in PD may result from impairment of comparison of structural representations of presented faces with stored representations of faces known to the observer.     

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.     

Event-related potentials reflect heterogeneity of developmental prosopagnosia

Event-related potential (ERP) studies of developmental prosopagnosia (DP) are rare. Previous ERP investigations have reported smaller N170 amplitude differences between faces and objects in at least three prosopagnosics. The present study is based on a combination of behavioural and electrophysiological assessment of face processing. The aim was to investigate the face-specificity of the N170 in both healthy subjects and a group of DP individuals (N = 4), using famous and nonfamous faces, caricatures and houses as stimuli. All prosopagnosic subjects showed impairments in recognition of famous faces, memory for faces and learning new faces in behavioural assessment. In healthy subjects the largest effects were found at parieto-occipital electrode positions (PO7 and PO8), along with a familiarity effect at these electrode positions. Thus, parieto-occipital areas appear to play an important role in face processing. Three prosopagnosics showed reliable N170 amplitude differences between faces and nonface stimuli, whereas one DP individual showed significantly reduced amplitude differences between faces and nonface objects. The behavioural and electrophysiological data support the idea that DP reflects a heterogeneous impairment and that face processing deficits are not necessarily correlated with a lack of face-specific N170.     

An event-related potential study of contextual modifications in a face recognition task

Event-related potentials (ERP) were recorded during a task involving the short-term recognition of unfamiliar faces. The purpose was to study the effects of changing the intrinsic context (facial expression) and/or the extrinsic context (background) between the encoding and recognition of a face. The new face caused an increase in the parietal N170 amplitude, but this component was not affected by contextual modifications. In contrast, the frontal N200 was very sensitive to context changes. There was also a well-defined, late parietal component modulated by the processing of information relevant to the face recognition decision. This late positive component reached its amplitude peak when the decision criterion was the strictest. The results obtain showed that ERP can be modulated by these context variations even though they are irrelevant to the task at hand.     

Facial emotion recognition in schizophrenia: when and why does it go awry?

OBJECTIVE: Schizophrenia patients demonstrate impaired emotional processing that may be due, in part, to impaired facial emotion recognition. This study examined event-related potential (ERP) responses to emotional faces in schizophrenia patients and controls to determine when, in the temporal processing stream, patient abnormalities occur. METHOD: 16 patients and 16 healthy control participants performed a facial emotion recognition task. Very sad, somewhat sad, neutral, somewhat happy, and very happy faces were each presented for 100 ms. Subjects indicated whether each face was "Happy", "Neutral", or "Sad". Evoked potential data were obtained using a 32-channel EEG system. RESULTS: Controls performed better than patients in recognizing facial emotions. In patients, better recognition of happy faces correlated with less severe negative symptoms. Four ERP components corresponding to the P100, N170, N250, and P300 were identified. Group differences were noted for the N170 "face processing" component that underlies the structural encoding of facial features, but not for the subsequent N250 "affect modulation" component. Higher amplitude of the N170 response to sad faces was correlated with less severe delusional symptoms. Although P300 abnormalities were found, the variance of this component was explained by the earlier N170 response. CONCLUSION: Patients with schizophrenia demonstrate abnormalities in early visual encoding of facial features that precedes the ERP response typically associated with facial affect recognition. This suggests that affect recognition deficits, at least for happy and sad discrimination, are secondary to faulty structural encoding of faces. The association of abnormal face encoding with delusions may denote the physiological basis for clinical misidentification syndromes.