Abstract
The amplitude of the Steady State Visual Evoked Potential (SSVEP) response at a specific stimulation frequency is larger over right occipito-temporal cortex when different faces are presented compared to when identical faces are presented (Rossion & Boremanse, 2011, JOV). Such SSVEP sensibility to variations in facial identity is observed for stimulation frequencies between 3Hz and 10Hz and is maximum at about 6Hz (Alonso-Prieto,., and Rossion, JOV, 2011 vol. 11, 643). Currently, it is not known whether this effect is modulated by the presence of internal and external facial features, e.g. skin color and hair. This issue is relevant for the validity of the SSVEP approach in face perception research because the appearance of the facial stimuli, which is frequently manipulated in face perception studies, can influence the SSVEPs. Six observers were confronted with a sequence of faces (15s of identical faces followed by 69s of either identical or different faces) presented at 4.00Hz (or faces/second, one cycle = 250 ms) and 5.88Hz (one cycle = 170 ms) while high-density EEG (128 channels) was recorded. Four types of faces were presented: 3D laser-scans pictures, full color pictures with external features, color and grayscale photographs with cropped external features. The SSVEP response at the stimulation frequency was larger for different than identical faces for all stimulus types. At 5.88Hz, the strongest response was obtained for different full-color faces with external features. Time-course analysis of EEG data showed that the response at the stimulation frequency increased until about 10s and then decreased when the same face identity was presented. It immediately reincreased when different faces were introduced (16th second). These observations indicate a fast, large and stimulation frequency-specific release to face identity adaptation in the human brain and corroborate the reliability of the SSVEP approach to study face perception processes.
Meeting abstract presented at VSS 2012