Electrophysiological studies of human face perception. III: Effects of top-down processing on face-specific potentials

This is the last in a series of papers dealing with intracranial event rela ted potential (ERP) correlates of face perception. Here we describe the res ults of manipulations that may exert top-down influences on face recognitio n and face-specific ERPs, and the effects of cortical stimulation at face-s pecific sites. Ventral face-specific N200 was not evoked by affective stimu li; showed little or no habituation; was not affected by the familiarity or unfamiliarity of faces; showed no semantic priming; and was not affected b y face-name learning or identification. P290 and N700 were affected by sema ntic priming and by face-name learning and identification. The early fracti on of N700 and face-specific P350 exhibited significant habituation. About half of the AP350 sites exhibited semantic priming, whereas the VP350 and L P350 sites did not. Cortical stimulation evoked a transient inability to na me familiar faces or evoked face-related hallucinations at two-thirds of fa ce-specific N200 sites. These results are discussed in relation to human be havioral studies and monkey single-cell recordings. Discussion of results o f all three papers concludes that: face-specific N200 reflects the operatio n of a module specialized for the perception of human faces; ventral and la teral occipitotemporal cortex are composed of a complex mosaic of functiona lly discrete patches of cortex of variable number, size and location; in ve ntral cortex there is a posterior-to-anterior trend in the location of patc hes in the order letter-strings, form, hands, objects, faces and face parts : P290 and N700 at face-specific N200 sites, and face-specific P350, are su bject to top down influences.