The temporal context of face perception : behavioural, electrophysiological and neuroimaging correlates
Adaptation-related aftereffects (AEs) and repetition priming (PR) are two phenomena when recent experiences alter face perception. Although the behavioural reflections of AEs and PR are quite different, both phenomena share some similarities regarding their functional properties and neural correlates. As most of the previous studies focused on either one or the other phenomenon, little is known about the relationship between AEs and PR. The present studies attempted to fill this gap. Study I investigated face identity AEs and PR within the same stimulus repetition paradigm, keeping timing and task constant. Following face or Fourier phase randomized (noise) stimuli, participants classified test faces varying on a morph continuum between two famous identities. Study I showed that AEs and PR can be observed within the same paradigm and subjects, behaviourally and in event-related potentials (ERPs). Interestingly, we found identity-specific as well as category-specific ERP modulations. Study II further investigated the factors underlying face identity AEs in a similar paradigm. The results confirmed and extended the findings of Study I, e.g., there were again different ERP modulations by stimulus category and face identity. In Study III, AEs and image-specific PR were investigated in the perception of face gender using functional magnetic resonance imaging (fMRI). Study III suggested dissociations between 1) gender-specific AEs and image-specific PR in behaviour, 2) brain areas associated with AEs and PR, and 3) brain areas associated with gender-specific and categorical processes. In conclusion, the present studies showed that similarity between adaptor and test faces and ambiguity of the test face both determine whether AE or PR is observed, and suggested that exclusive mechanisms might underlie both phenomena. Our results also revealed that the processing of face identity or gender runs in parallel to object-category processing during the earlier processing stages.