Data from the paper entitled: "Short-term EEG dynamics and neural generators evoked by navigational images" Files structure is as stated in: filestructure.txt Data studies and analysis generated in eeglab for high density EEG recorded from navigational images.All recordings were unipolar against the left earlobe electrode Vertical eye movements (EOG) were recorded unipolarly against the common reference and horizontal EOG was recorded bipolarly. All electrode impedances were maintained below 5 kΩ. Scalp potentials were amplified by ANT DC-amplifiers (ANT, the Netherlands) and digitized with a rate of 2.048 Hz, a resolution of 16 bit (range 11 mV). A band pass from DC to 256 Hz and a notch filter (47.5-52.5 Hz) were also applied.
Cette etude vise a analyser les relations entre les emotions (etat et trait) et l'action dans le cadre de la production d'un mouvement volontaire de l'ensemble du corps : l'initiation du simple pas. La tâche des participants (n = 24, âge : 18-31 ans) consistait a initier le simple pas pendant la presentation de visages emotionnels au cours de deux conditions experimentales realisees de facon aleatoire. Dans la condition explicite, les participants devaient avancer si le visage presente exprimait la peur, la colere et la joie ou rester immobiles si le visage etait « neutre ». Dans la condition implicite, la moitie des participants avait pour consigne d'avancer si le visage presente etait une femme ou de rester immobile s'il s'agissait d'un homme (en ignorant l'emotion du visage). La consigne inverse etait donnee a l'autre moitie des participants. A la fin de l'experimentation, le trait de colere des participants ainsi que l'intensite percue des visages emotionnels etaient mesures. Les analyses realisees a partir d'un modele mixte a quatre effets fixes (condition, emotion, trait de colere, intensite) et deux effets aleatoires (celui des participants et celui des visages sur l'intercept) mettent en avant deux principaux resultats. Premierement, alors qu'aucune difference de performance (i.e. un temps necessaire pour atteindre le pic de vitesse plus court, tV) n'est observee dans les conditions explicite et implicite face aux visages exprimant la peur, une meilleure performance du mouvement est constatee face aux visages exprimant la colere et la joie dans la condition implicite comparativement a la condition explicite. Deuxiemement, une reduction du tV est observee avec l'augmentation du trait de colere pour les stimuli d'intensites percues comme faible et moyenne. Ces resultats suggerent un traitement automatique des visages exprimant la peur qui n'interfere pas sur l'initiation du simple pas et un lien entre le trait de colere des individus et les comportements d'approche.
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.
The processing of emotional facial expressions has been studied mainly with stereotypical face stimuli, but contextual information leads to drastic modulation in the categorization of facial expressions (Aviezer et al., 2017). In the human brain, brief facial expression changes are quickly read from faces (Dzhelyova et al., 2017). Yet, how reliably these changes are detected with realistic faces embedded in a natural context remain unknown. 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 a neutral-expression face 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 (e.g ANeutralANeutralANeutralANeutralANeutralBExpressiveANeutral …). 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. Despite the wide variety across images, a F/5 response was observed for each individual participant, pointing to robust facial expression categorization processes. At the 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. Despite evidence (Leleu et al., 2018; Hinojosa et al., 2015) suggesting that sad expressions are more subtle and thus lead to weaker responses than other emotions, our observations with natural expressions highlight a stronger response for this emotion, especially over the left hemisphere. Moreover, we observed a right hemisphere dominance for a shift from neutral to fearful faces and a left hemisphere dominance for a shift from neutral to happy faces.
Recognizing a familiar person from his/her face is a fundamental brain function. Surprisingly, to date the actual speed of categorizing a face as familiar remains largely unknown. Here we seek to clarify this question by using a Go/No-go familiarity judgment task with photographs of personally familiar (same classroom as the participant) and well-matched pictures of unfamiliar faces, which required speeded responses to individually presented face stimuli. During the recording of high-density event-related potentials (ERP, 128 channels), two groups of young adult participants were instructed either to respond when a photograph of a personally familiar face was presented (n = 11, 6 females), or when the face was unfamiliar (n = 12, 7 female). Face stimuli contained external features (hair), but external indicators of identity were carefully removed (clothes, ….). Each face stimulus appeared for 100ms, followed by a blank screen (1500-1700ms). Behaviorally, faces could be classified as familiar as early as 310-320ms (average RT, 450 ms), about 80ms faster than when unfamiliar face categorization was required. ERP differential waveforms between Go and No-go responses when detecting familiarity showed the earliest difference at occipito-temporal cortex shortly after 200 ms, starting in the right hemisphere, and 10 ms later in the left hemisphere. Differences appeared about 50 ms later for the Go-unfamiliar decision task, with no differences in lateralization of onset times. There were no clear effects of face familiarity on earlier visual event-related potentials (P1, N170). These earliest effects observed in electrophysiological recordings are compatible with the behavioral output taking place at about 100 ms later. They indicate that the human brain needs no more than 200ms following stimulus onset to recognize a familiar person based on his/her face only, a time frame that puts strong constraints on the time-course of face processing operations in the human brain.
