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Neuropsychological studies have shown that prosopagnosic individuals perceive face structure in an atypical way. This might preclude the formation of appropriate face representations and, consequently, hamper effective recognition. The present ERP study, in combination with Bayesian source reconstruction, investigates how information related to both external (E) and internal (I) features was processed by E.C. and I.P., suffering from acquired and developmental prosopagnosia, respectively. They carried out a face-feature matching task with new faces. E.C. showed poor performance and remarkable lack of early face-sensitive P1, N170 and P2 responses on right (damaged) posterior cortex. Although she presented the expected mismatch effect to target faces in the E-I sequence, it was of shorter duration than in Controls, and involved left parietal, right frontocentral and dorsofrontal regions, suggestive of reduced neural circuitry to process face configurations. In turn, I.P. performed efficiently but with a remarkable bias to give “match” responses. His face-sensitive potentials P1–N170 were comparable to those from Controls, however, he showed no subsequent P2 response and a mismatch effect only in the I-E sequence, reflecting activation confined to those regions that sustain typically the initial stages of face processing. Relevantly, neither of the prosopagnosics exhibited conspicuous P3 responses to features acting as primes, indicating that diagnostic information for constructing face representations could not be sufficiently attended nor deeply encoded. Our findings suggest a different locus for altered neurocognitive mechanisms in the face network in participants with different types of prosopagnosia, but common indicators of a deficient allocation of attentional resources for further recognition.

The global precedence effect (GPE), originally referring to processing hierarchical visual stimuli composed of letters, is characterised by both global advantage and global interference. We present herein a study of how this effect is modulated by the variables letter and sex. The Navon task, using the letters “H” and “S,” was administered to 78 males and 168 females (69 follicular women, 52 luteal women, and 47 hormonal contraceptive users). No interaction occurred between the letter and sex variables, but significant main effects arose from each of these. Reaction times (RTs) revealed that the letter “H” was identified more rapidly in the congruent condition both in the global and the local task, and the letter “S” in the incongruent condition for the local task. Also, although RTs showed a GPE in both males and females, males displayed shorter reaction times in both global and local tasks. Furthermore, luteal women showed higher d’ index (discrimination sensitivity) in the congruent condition for the local task than both follicular women and hormonal contraceptive users, as well as longer exploration time of the irrelevant level during the global task than males. We conclude that, according to the linear periodicity law, the GPE is enhanced for compound letters with straight vs. curved strokes, whereas it is stronger in males than in females. Relevantly, luteal phase of the menstrual cycle seems to tilt women to rely on finer grained information, thus exhibiting an analytical processing style in global/local visual processing, This work was supported by Grant PGC2018-094937-B-100 from the Ministerio de Ciencia, Innovación y Universidades de España and research contracts supported by Comunidad de Madrid and co-financed by the European Social Fund (PEJD-2017- PRE/SOC-4240, PEJD-2018-PRE/SOC-9185, and PEJD-2018- PRE/SOC-8992).

Appraisal theories of emotion sustain that stimuli containing high biological relevance preferentially capture our attention, regardless of their valence. In this work, we study the priming effect of both cute and threatening pictures on global/local visual processing. Seventy-eight males and 168 females in different menstrual cycle phases performed the global/local Navon letter task immediately after observing cute (infants and baby animals), threatening (animals in aggressive poses) or neutral pictures. Hierarchical stimuli were made up of global and local letters that could be either congruent (e.g. global H, localH) or incongruent (e.g. global H, localS). While we observed no interaction between affective primes and sex/menstrual cycle phase, each of these variables did have an independent effect on the global/local task. Thus, letter identification was significantly slower in the global task (only) after cute vs. neutral primes. Relevantly, the local-minus-global RT index revealed an attentional narrowing after both cute and threatening primes (vs. neutral primes) in incongruent trials. As for sex effects, a facilitation of global vs. local processing was observed in both sexes. However, women registered slower RTs than men, whereas women in the luteal phase showed faster RTs than those in follicular phase in the local task. This suggests that women, mainly those in their luteal menstrual phase, tend to rely on a more analytical style of processing while attending to hierarchical stimuli. Most importantly, stimuli containing high biological significance drive narrowing of the attentional focus in global/local visual processing, especially in conditions of higher attentional demand.

Event related potentials (ERPs) provide precise temporal information about cognitive processing, but with poor spatial resolution, while functional magnetic resonance imaging (fMRI) reliably identifies brain areas involved, but with poor temporal resolution. Here we use fMRI to guide source localization of the ERPs at different times for studying the temporal dynamics of the neural system for recognizing familiar faces. fMRI activation areas were defined in a previous experiment applying the same paradigm used for ERPs. The Bayesian model averaging (BMA) method was used to estimate the generators of the ERPs to unfamiliar, visually familiar, and personally-familiar faces constraining the model by fMRI activation results. For this, higher prior probabilities in the solution space were assigned to the fMRI-defined regions, which included face-selective areas and other areas related to “person knowledge” retrieval. Source analysis was carried out in three-time windows: early (150–210 ms), middle (300–380 ms) and late (460–580 ms). The early and middle responses were generated in fMRI-defined areas for all face categories, while these areas do not contribute to the late response. Different areas contributed to the generation of the early and middle ERPs elicited by unfamiliar faces: fusiform (Fus), inferior occipital, superior temporal sulcus and the posterior cingulate (PC) cortices. For familiar faces, the contributing areas were Fus, PC and anterior temporal areas for visually familiar faces, with the addition of the medial orbitofrontal areas and other frontal structures for personally-significant faces. For both unfamiliar and familiar faces, more extended and reliable involvement of contributing areas were obtained for the middle compare with early time window. Our fMRI guide ERP source analysis suggested the recruitment of person-knowledge processing areas as early as 150–210 ms after stimulus onset during recognition of personally-familiar faces. We concluded that fMRI-constrained BMA source analysis provide information regarding the temporal-dynamics in the neural system for cognitive processsing.

We analyze the functional significance of different event-related potentials (ERPs) as electrophysiological indices of face perception and face recognition, according to cognitive and neurofunctional models of face processing. Initially, the processing of faces seems to be supported by early extrastriate occipital cortices and revealed by modulations of the occipital P1. This early response is thought to reflect the detection of certain primary structural aspects indicating the presence grosso modo of a face within the visual field.The posterior-temporal N170 is more sensitive to the detection of faces as complex-structured stimuli and, therefore, to the presence of its distinctive organizational characteristics prior to within-category identification. In turn, the relatively late and probably more rostrally generated N250r and N400-like responses might respectively indicate processes of access and retrieval of face-related information, which is stored in long-term memory (LTM). New methods of analysis of electrophysiological and neuroanatomical data, namely, dynamic causal modeling, single-trial and time-frequency analyses, are highly recommended to advance in the knowledge of those brain mechanisms concerning face processing, This work was supported by “Ministerio de Economía y Competitividad” (Spain, I + D + I National Programme, PSI2013-46007-P)

Background/Study Context: Patients with mild Alzheimer's disease and mild cognitive impairment show selective loss of knowledge regarding facial identification. Methods: The authors focus on decline effects on event-related potentials (ERPs) P100, N170, N250, and N400, associated with the processing of facial identity. Different famous and unknown faces were presented in explicit and implicit familiarity tasks. Results: Patients with cognitive impairment showed modulations on P100 and N170 and greater activity in prefrontal areas in the earlier component. In healthy elderly individuals, but not in patients, famous faces modulated the long-latency ERPs N250 and N400, related to the access and retrieval of stored facial-related information, respectively. Conclusion: ERPs have potential as markers of neurodegenerative disease such as dementia. The neural systems supporting facial identification may differ in normal and cognitively impaired older adults.

Brain activity underlying explicit and implicit processing of face familiarity was assessed by Event-Related Potentials (ERPs) elicited by famous and unknown faces with happy or neutral expressions. A set of faces was presented in a familiarity judgment (explicit) task and another in an expression judgment (implicit familiarity) task. After recording, these tasks were repeated exchanging the stimuli, and post-recording behavioral data from the familiarity task were used for re-averaging EEG segments from the expression task. Both explicit and implicit processing of famous faces resulted in an enhanced N250. Explicit processing of famous faces was specifically associated with earlier N400 and P600, with increased activity within brain areas involved in identity processing around 250 and 450 ms. These findings suggest different brain dynamics for explicit and implicit face processing, and that implicit processing of the identity in the context of an expression task is mainly associated with the transient activation of face representations in memory.

Thirty scalp sites were used to investigate the specific topography of the event-related potentials (ERPs) related to face associative priming when masked eyes of familiar faces were completed with either the proper features or incongruent ones. The enhanced negativity of N210 and N350, due to structural incongruity of faces, have a “category specific” inferotemporal localization on the scalp. Additional analyses support the existence of multiple ERP features within the temporal interval typically associated with N400 (N350 and N380), involving occipitotemporal and centroparietal areas. Seven reliable dipole locations have been evidenced using the brain electrical source analysis algorithm. Some of these localizations (fusiform, parahippocampal) are already known to be involved in face recognition, the other ones being related to general cognitive processes related to the task's demand. Because of their specific topography, the observed effects suggest that the face structural congruency process might involve early specialized neocortical areas in parallel with cortical memory circuits in the integration of perceptual and cognitive face processing.

In a previous study [E. Olivares, M.A. Bobes, E. Aubert, M. Valdés-Sosa, Associative ERPs effects with memories of artificial faces, Cogn. Brain Res. 2 (1994) 39-48] we reported the presence of a negativity associated with mismatching features when subjects carried out a face-feature matching task whilst their evoked potentials were recorded. Since the stimuli used were learned faces (realistic drawings), for which the subjects possessed no semantic information or associated verbal labels, the mismatch negativity obtained was considered a face-specific N400. In this work we present a new experiment to study the topographic distribution of these mismatch effects. As in the above-mentioned study, in each trial the subjects observed previously an incomplete (without the eyes/eyebrows fragment) familiar face, which served as a structural context for the face recognition. The face was then completed by grafting either matching (learned) features or mismatching features (from another face). In line with neuropsychological studies on prosopagnosia and electrophysiological findings in humans and non-human primates, we found as one of the most relevant items of data that the most-posterior (principally, left occipital) cortices appear to be a region in which are located the possible neural generators of the negativity associated with the detection of incongruencies in the structure of familiar faces. We also reported a late positivity, distributed in more anterior regions, which follows the mismatch negativity. This complex N-P is interpreted as reflecting a dual process of retrieval and integration of information in memory.

In face processing tasks, prior presentation of internal facial features, when compared with external ones, facilitates the recognition of subsequently displayed familiar faces. In a previous ERP study ( Olivares & Iglesias, 2010 ) we found a visibly larger N400-like effect when identity mismatch familiar faces were preceded by internal features, as compared to prior presentation of external ones. In the present study we contrasted the processing of familiar and unfamiliar faces in the face-feature matching task to assess whether the so-called “internal features advantage” relies mainly on the use of stored face-identity-related information or if it might operate independently from stimulus familiarity. Our participants (N = 24) achieved better performance with internal features as primes and, significantly, with familiar faces. Importantly, ERPs elicited by identity mismatch complete faces displayed a negativity around 300–600 msec which was clearly enhanced for familiar faces primed by internal features when compared with the other experimental conditions. Source reconstruction showed incremented activity elicited by familiar stimuli in both posterior (ventral occipitotemporal) and more anterior (parahippocampal (ParaHIP) and orbitofrontal) brain regions. The activity elicited by unfamiliar stimuli was, in general, located in more posterior regions. Our findings suggest that the activation of multiple neural codes is required for optimal individuation in face-feature matching and that a cortical network related to long-term information for face-identity processing seems to support the internal feature effect.

The perceptual processing of faces was studied using event-related potentials (ERPs) in 12 elderly patients with cognitive impairment, 15 elderly adults and 16 young adults in order to explore the sensitivity of N170/VPP to the cognitive decline associated to Alzheimer's disease. Famous and unknown faces were presented in a familiarity categorization task. Eight patients and 11 elderly adults repeated this task to obtain longitudinal data. Topographical effects were analyzed using PCA. The posterior N170 showed reduced amplitude in patients with cognitive impairment and elderly adults, compared to young adults, which could indicate perceptual impairment in configural face-encoding processing. The anterior VPP showed enhanced amplitude in patients with cognitive impairment, compared to young and elderly adults, which might relate to the prefrontal dysfunction associated to mild dementia. These preliminary findings suggest that N170/VPP could be modulated by the decline related to pathological cognitive aging.

Expectancies about face-structure can be induced by viewing parts of faces, which generates constraints due to two types of knowledge: feature-content and configuration. In a first experiment ERPs were recorded when parts of familiar faces were completed with incongruent features (from another face), as opposed to congruent features (from the same face). All features were in the correct configuration. An enhanced negativity was found for incongruent completions (N374) that was larger over the right side of the scalp. This replicates the results of Valdes-Sosa and Bobes (1990). In another two experiments, ERPs were recorded when parts of familiar faces were completed by congruent features, but sometimes placed in an incorrect position. In one experiment the features were jumbled; in the other, the features were slightly displaced. These configuration distortions were associated to late positive components, with a maxima at the centro-parietal region, of equal amplitude for both kinds of configuration anomalies. The N374 component seems to be a non-linguistic analog of the N400. The different ERP signatures for expectancy violations of configuration and feature-content suggest that these types of information are processed separately at some stages.

Whereas some behavioral studies have shown that internal features are crucial for efficient face recognition in healthy adults, compared to external features, the brain mechanisms underlying this “internal features advantage” are still unknown. In the present study, the differential relevance of both subsets of facial features is addressed analyzing N400-like potentials elicited in a face-feature matching task, where external or internal features and complete face targets were displayed consecutively in each trial. Experiment 1 revealed a larger and longer-lasting N400-like effect with the prior presentation of internal features, which suggests more efficient processing of long-term face-related information. An analysis of neural sources in Experiment 2 revealed greater activation of frontal and left temporal brain areas in the processing of mismatching targets when preceded by internal features. Thus, brain electrical correlates of the “internal features advantage” could be verified around 300-400 ms post-stimulus and supported by a face-identity related neural network.

In this ERP study we analyzed how different orders of presentation of external and internal features influence the integration of facial components into face gestalts. Participants carried out a face-feature matching task in which, in each trial, external (E) and internal (I) facial features were presented separately and in sequence, followed by a complete unfamiliar face (matching or mismatching). For the E-I group of participants the order of presentation was external features, internal features and then the complete face. The I-E group viewed the internal features first. Mismatch effects in complete faces were more conspicuous and lasted from about 300 to 600 ms with the order E-I, while those with the order I-E were scarcely observable, and significant only from 450 to 470 ms. The external features tended to elicit a larger P150, while the N170 was preferentially associated with the internal ones. A P360, probably indicating stimulus relevance, was present in both groups for external features, while it was associated with internal features only in the I-E group. These results suggest that in the E-I order the binding of facial features into a single face representation occurs according to a stepwise process which facilitates the integration. In turn, in the I-E order the processing related to the two sets of features appears more dissociated and is of a more componential nature. Moreover, we propose that the external features may be especially relevant for object categorization, while internal features would be more closely related to subsequent configural mechanisms.

Event-related potentials (ERPs) were used to investigate the role of attention on the processing of facial expressions of fear and disgust. Stimuli consisted of overlapping pictures of a face and a house. Participants had to monitor repetitions of faces or houses, in separate blocks of trials, so that object-based attention was manipulated while spatial attention was kept constant. Faces varied in expression and could be either fearful or neutral (in the fear condition) or disgusted or neutral (in the disgust condition). When attending to faces, participants were required to signal repetitions of the same person, with the facial expressions being completely irrelevant to the task. Different effects of selective attention and different patterns of brain activity were observed for faces with fear and disgust expressions. Results indicated that the perception of fear from faces is gated by selective attention at early latencies, whereas a sustained positivity for fearful faces compared to neutral faces emerged around 160ms at central-parietal sites, independent of selective attention. In the case of disgust, ERP differences began only around 160ms after stimulus onset, and only after 480ms was the perception of disgust modulated by attention allocation. Results are interpreted in terms of different neural mechanisms for the perception of fear and disgust and related to the functional significance of these two emotions for the survival of the organism.

N400 brain event-related potential (ERP) is a mismatch negativity originally found in response to semantic incongruences of a linguistic nature and is used paradigmatically to investigate memory organization in various domains of information, including that of faces. In the present study, we analyzed different mismatch negativities evoked in N400-like paradigms related to recognition of newly learned faces with or without associated verbal information. ERPs were compared in the following conditions: (1) mismatching features (eyes –eyebrows) using a facial context corresponding to the faces learned without associated verbal information (‘‘pure’’ intradomain facial processing); (2) mismatching features using a facial context corresponding to the faces learned with associated occupations and proper names (‘‘nonpure’’ intradomain facial processing); (3) mismatching occupations using a facial context (cross-domain processing); and (4) mismatching names using an occupation context (intradomain verbal processing). Results revealed that mismatching stimuli in the four conditions elicited a mismatch negativity analogous to N400 but with different timing and topographical patterns. The onset of the mismatch negativity occurred earliest in Conditions 1 and 2, followed by Condition 4, and latest in Condition 3. The negativity had the shortest duration in Task 1 and the longest duration in Task 3. Bilateral parietal activity was confirmed in all conditions, in addition to a predominant right posterior temporal localization in Condition 1, a predominant right frontal localization in Condition 2, an occipital localization in Condition 3, and a more widely distributed (although with posterior predominance) localization in Condition 4. These results support the existence of multiple N400, and particularly of a nonlinguistic N400 related to purely visual information, which can be evoked by facial structure processing in the absence of verbal –semantic information This work was supported by Comunidad Autónoma de Madrid (grant 06/0168/2000) and Ministerio de Ciencia y Tecnología de España (grant BSO2000-0114) SI

Event-related potentials (ERPs) and behavioral data were recorded while subjects performed two tasks on the same set of faces (presented in pairs). One task was identity matching and the other expression matching. Two groups of subjects participated, one familiar and the other unfamiliar with the faces. Subjects were less accurate in matching expressions than identity. Familiarity facilitated identity but not expression matching. ERPs to mismatches in both tasks elicited a negativity around 400 ms, which was similar in latency and amplitude in the two tasks, but differed in scalp topography. Whereas the mismatch negativity had the same landscape over the left hemisphere for both tasks, the component related to expression had larger amplitudes over the right-temporal regions. Familiarity had no effect on these negativities, although it affected a late positivity (LP). These results support the idea of distinct neural systems subserving face processing, and agree with a role of the right hemisphere for the processing of emotional expressions.

A previous study (Valdes-Sosa and Bobes, 1990) described a negative ERP component evoked by mis-matches in a face-feature matching task, using photographs of real faces. This component could be N400 (or an analogue), elicited by associative priming within a non-linguistic domain: that of face structure. To confirm this it is necessary to demonstrate that semantic/linguistic recoding was not a necessary condition in triggering the negativity. This means falsifying what we call the 'priming by proxy' hypothesis, and locating the triggering mis-match within face structure. In this paper subjects studied artificial schematic faces over several sessions, and 1 week later were presented with a face-feature matching task with simultaneous ERP recording. Since no semantic information or verbal labels were available, eliciting a mis-match negativity with these faces contradicts the 'priming by proxy' hypothesis. In a first experiment, in which the subjects learning was controlled through a face familiarity decision task, no significant mis-match negativity was found. However, in a second experiment in which learning was controlled through a forced-choice face-feature match, a significant mis-match negativity was found in the subsequent recording session. This result supports the idea that a component similar to N400 can be elicited by an associative mis-match restricted to the face-structural domain.

OBJECTIVE To analyze the neural bases of perception and the recognition of faces. First of all we consider the concept of functional hemisphere specialization; then we look at the results obtained with regard to the neuroanatomy of processing faces and finally refer to the disorders of recognition of faces in humans. For this we review the clinical evidence obtained from the neuropsychological studies of prosopagnostic patients and the data derived from psychophysiological experiments done using intracranial recordings of nonhuman primates. DEVELOPMENT The agreement between the results analysed allows us conclude that in both cerebral hemispheres there are neural mechanisms specialized in the perception and recognition of faces, and in particular the ventral and posterior regions of the occipito-temporal cortex play a decisive part in these processes. Similarly experimental findings in nonhuman primates permits explanation of the neural nature of certain neuropsychological disorders seen in man, such as the case of the dissociation between disorders of the recognition of facial identity and disorders of recognition of emotional expression, and also dissociation between the difficulty in recognizing familiar faces and difficulty in recognizing non-familiar faces. CONCLUSION The use of modern neuroimaging techniques and electrophysiological studies using evoked potentials are necessary for greater understanding of these and other disorders related to processing facial information.