Abstract
Humans have an astonishing ability to rapidly and automatically recognize a face as being familiar among a crowd of unfamiliar faces. To capture this process while mimicking the rapid processing strain we experience in daily life, we used a Fast Periodic Visual Presentation (FPVS) approach coupled with electroencephalography (EEG). Fifteen participants viewed 12 sequences of natural images of different unfamiliar faces alternating at a frequency of 6 Hz (i.e., 6 faces by second) over 70 s. Variable familiar faces (i.e., different face images of French celebrities) appeared every 7th image. Participants were unaware of the goal of the study and performed an orthogonal task of responding to color change of a central fixation cross. A robust familiar-unfamiliar discrimination response was objectively identified in the EEG spectrum exactly at 6/7 Hz (0.857 Hz) and its harmonics over bilateral occipito-temporal regions, in all individual participants. Image variability ensured that this familiarity face response was not due to low-level cues, as confirmed by its large reduction for faces presented upside down (about 15% of the response to upright faces, barely above noise level). Fourteen out of 15 subjects had significant face inversion effect over either unilateral or bilateral OT region. The familiarity face response started at about 200ms following stimulus onset and lasted for about half a second. By providing a robust index of human ability to rapidly and automatically recognize a face as being familiar among unfamiliar faces, our study opens new perspectives for understanding the nature and spatio-temporal course of this function as well as for characterizing it in clinical and developmental populations.
Meeting abstract presented at VSS 2018