The dynamics of adaptation to fast periodic visual stimulation

Abstract

A recent study showed that electrical (EEG) response to fast periodic visual stimulation (FPVS, i.e., 4 Hz) recovers immediately when a different face identity is presented in a periodic train of identical faces (Rossion et al., 2012, NeuroImage). The effect, localized over the right occipito-temporal cortex (OTC) and specific to the stimulation frequency, is much reduced when faces are inverted or contrast-reversed. These findings showed that FPVS represents a powerful tool for estimating visual cortex sensitivity to high-level visual manipulations. The present study was designed to clarify further the temporal dynamics of the fast periodic adaption itself. It was based on the hypothesis that initially, periodic presentation of exactly identical faces tends to induce stronger and faster response entrainment than different face identities (Rossion and Boremanse, 2011), counteracting visual adaptation effects. Here the onset of periodic response and adaptation were separated by reversing the order of stimuli sequences: we induced the fast periodic response by presentation of different faces for 15 seconds, and then introduced identical faces to study the dynamics of adaptation after the system has been periodically entrained. Thirteen subjects were presented with 74-s trials (with 15-s long initial different faces sequences) in which faces appeared at a constant rate of 5.88 Hz and high-density (128 channels) EEG signal was recorded. Compared to a sequence in which only different faces were presented, we found large adaptation effects (i.e., reduction of EEG amplitude at the periodic rate of stimulation) to the repetition of the same face identity, mainly over the right occipito-temporal cortex. However, contrary to the fast release from adaptation observed previously (Rossion et al., 2012), the amplitude reduction took several seconds following the introduction of a repeated face, suggesting that generalization to the same face identity has a slower temporal dynamics than detection of changes of identities. Meeting abstract presented at VSS 2013