Early (n170/m170) face-sensitivity despite right lateral occipital brain damage in acquired prosopagnosia.

Compared to objects, pictures of faces elicit a larger early electromagnetic response at occipito-temporal sites on the human scalp, with an onset of 130 ms and a peak at about 170 ms. This N170 face effect is larger in the right than the left hemisphere and has been associated with the early categorization of the stimulus as a face. Here we tested whether this effect can be observed in the absence of some of the visual areas showing a preferential response to faces as typically identified in neuroimaging. Event-related potentials were recorded in response to faces, cars, and their phase-scrambled versions in a well-known brain-damaged case of prosopagnosia (PS). Despite the patient's right inferior occipital gyrus lesion encompassing the most posterior cortical area showing preferential response to faces ("occipital face area"), we identified an early face-sensitive component over the right occipito-temporal hemisphere of the patient that was identified as the N170. A second experiment supported this conclusion, showing the typical N170 increase of latency and amplitude in response to inverted faces. In contrast, there was no N170 in the left hemisphere, where PS has a lesion to the middle fusiform gyrus and shows no evidence of face-preferential response in neuroimaging (no left "fusiform face area"). These results were replicated by a magnetoencephalographic investigation of the patient, disclosing a M170 component only in the right hemisphere. These observations indicate that face-preferential activation in the inferior occipital cortex is not necessary to elicit early visual responses associated with face perception (N170/M170) on the human scalp. These results further suggest that when the right inferior occipital cortex is damaged, the integrity of the middle fusiform gyrus and/or the superior temporal sulcus - two areas showing face-preferential responses in the patient's right hemisphere - might be necessary to generate the N170 effect

Etre parent d'enfant atteint des troubles du spectre de l'autisme : Le stress parental à travers l'analyse interprétative phénoménologique.

International audienceL’objectif de notre étude était de faire partager l’expérience de parents, expériences de vie etd’accompagnement de leur enfant atteint des troubles du spectre de l’autisme, afin decomprendre les facteurs du stress parental tels qu’ils étaient perçus par les parents eux-mêmes.Cette recherche visait à élucider de quels éléments sont constitués le vécu des parents d’enfantsautistes, comment ces parents ont vécu l’expérience de vie suite au diagnostic de leur enfant etcomment ils ont su mettre en place « leur normalité » dans leur vie familiale

L'anxiété et les symptômes dépressifs chez les parents d'enfants atteints de syndrome de Dravet

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La perception des émotions en un simple coup d’oeil

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Perception des expressions émotionnelles : approche électrophysiologique par la stimulation périodique rapide.

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ERP evidence for the speed of face categorization in the human brain : disentangling the contribution of low-level visual cues from face perception

How fast are visual stimuli categorized as faces by the human brain? Because of their high temporal resolution and the possibility to record simultaneously from the whole brain, electromagnetic scalp measurements should be the ideal method to clarify this issue. However, this question remains debated, with studies reporting face-sensitive responses varying from 50 ms to 200 ms following stimulus onset. Here we disentangle the contribution of the information associated with the phenomenological experience of a face (phase) from low-level visual cues (amplitude spectrum, color) in accounting for early face-sensitivity in the human brain. Pictures of faces and of a category of familiar objects (cars), as well as their phase-scrambled versions, were presented to fifteen human participants tested with high-density (128 channels) EEG. We replicated an early face-sensitivity - larger response to pictures of faces than cars - at the level of the occipital event-related potential (ERP) P1 (80- ). However, a similar larger P1 to phase-scrambled faces than phase-scrambled cars was also found. In contrast, the occipito-temporal N170 was much larger in amplitude for pictures of intact faces than cars, especially in the right hemisphere, while the small N170 elicited by phase-scrambled stimuli did not differ for faces and cars. These findings show that sensitivity to faces on the visual evoked potentials P1 and N1 (N170) is functionally dissociated: the P1 face-sensitivity is driven by low-level visual cues while the N1 (or N170) face-sensitivity reflects the perception of a face. Altogether, these observations indicate that the earliest access to a high-level face representation, that is, a face percept, does not precede the N170 onset in the human brain. Furthermore, they allow resolving apparent discrepancies between the timing of rapid human saccades towards faces and the early activation of high-level facial representations as shown by electrophysiological studies in the primate brain. More generally, they put strong constraints on the interpretation of early (before 100 ms) face-sensitive effects in the human brain

The speed of recognition of personally familiar faces

Despite the generally accepted notion that humans are very good and fast at recognising familiar individuals from their faces, the actual speed with which this fundamental brain function can be achieved remains largely unknown. Here, two groups of participants were required to respond by finger-lift when presented with either a photograph of a personally familiar face (classmate), or an unfamiliar one. This speeded manual go/no-go categorisation task revealed that personally familiar faces could be categorised as early as 380 ms after presentation, about 80 ms faster than unfamiliar faces. When response times were averaged across all 8 stimulus presentations, we found that minimum RTs for both familiar and unfamiliar face decisions were substantially lower (310 ms and 370 ms). Analyses confirmed that stimulus repetition enhanced the speed with which faces were categorised, irrespective of familiarity, and that repetition did not affect the observed benefit in RTS for familiar over unfamiliar faces. These data, representing the elapsed time from stimulus onset to motor output, put constraints on the time course of familiar face recognition in the human brain, which can be tracked more precisely by high temporal resolution electrophysiological measures

Face familiarity decisions take 200 msec in the human brain: electrophysiological evidence from a go/no-go speeded task.

International audienceRecognizing a familiar face rapidly is a fundamental human brain function. Here we used scalp EEG to determine the minimal time needed to classify a face as personally familiar or unfamiliar. Go (familiar) and no-go (unfamiliar) responses elicited clear differential waveforms from 210 msec onward, this difference being first observed at right occipito-temporal electrode sites. Similar but delayed (by about 40 msec) responses were observed when go response were required to the unfamiliar rather than familiar faces, in a second group of participants. In both groups, a small increase of amplitude was also observed on the right hemisphere N170 face-sensitive component for familiar faces. However, unlike the post-200 msec differential go/no-go effect, this effect was unrelated to behavior and disappeared with repetition of unfamiliar faces. These observations indicate that accumulation of evidence within the first 200 msec poststimulus onset is sufficient for the human brain to decide whether a person is familiar based on his or her face, a time frame that puts strong constraints on the time course of face processing

The early visual encoding of a face (N170) is viewpoint-dependent: a parametric ERP-adaptation study.

Visual representations of faces are extracted shortly after 100 ms in the human brain, leading to an occipito-temporal cortex N170 event-related potential (ERP). To understand the nature of this early visual representation, a full-front adapting face preceded a different or identical target face identity. The target face varied parametrically in head orientation from the adapting face (0-90°, 15° steps). The N170 elicited by the target face increased progressively from 0° up to 30° head orientation, with no further increase until 90°. The N170 decreased for repeated face identities, this effect being stable between 0° and 30° changes of viewpoint, and no effect beyond that angle. These observations suggest that a face is encoded in a view-dependent manner, being matched to either a full-front or a profile face view. Yet, individual face representations activated as early as the peak of the N170 generalize partially across view

Human brain detection of natural brief facial expression at a single glance

Abstract published in Neurophysiologie Clinique, 49(3):199, June 2019National audienceBackground: The processing of emotional facial expressions has been studied mainly with stereotypical and posed face stimuli. In the human brain, brief facial expression changes are quickly read from faces (Dzhelyova et al., 2017).Objectives: The purpose of this study is to know how reliably brief changes are detected with realistic faces embedded in a natural context.Methods: In this study, faces varied in viewpoint, identity, gender, age, ethnic origin and background context. We recorded 128-channel EEG in 17 participants while they viewed 50s sequences with neutral-expression faces at a rate of 5.99 Hz (F) at two faces orientations (upright, inverted). Every five faces, the faces changed expression to one of the six basic expression (fear, disgust, happiness, anger, surprised or sadness; Ekman, 1993), one emotion per sequence. EEG responses at 5.99 Hz reflect general visual processing, while the EEG responses at F/5 = 1.1998 Hz and its harmonics (e.g., 2F/5 = 2.3996, etc.) index detection of a brief change of natural facial expression.Results: At group level, the categorization response was measured over occipito-temporal sites and was largely reduced when faces were inverted, indicating that it reflects high-level processes. Our observations with natural expressions highlight a stronger response for a shift from neutral to sad faces, especially over the left hemisphere. Moreover, we observed a right hemisphere dominance for fearful faces and a left hemisphere dominance for surprised faces.Conclusion: Human brain is able to detect automatically in natural scenes dynamic brief facial expression changes