The time course of repetition effects for familiar faces and objects: an ERP study.

Face and object priming has been extensively studied, but less is known about the repetition processes which are specific to each material and those which are common to both types of material. In order to track the time course of these repetition processes, EEG was recorded while 12 healthy young subjects performed a long-term perceptual repetition priming task using faces and object drawings. Item repetition induced early (N170) and late (P300 and 400-600 ms time-window) event-related potential (ERP) modulations. The N170 component was reduced in response to primed stimuli even with several hundred intervening items and this repetition effect was larger for objects than for faces. This early repetition effect may reflect the implicit retrieval of perceptual features. The late repetition effects showed enhanced positivity for primed items at centro-parietal, central and frontal sites. During this later time-window (400 and 600 ms at central and frontal sites), ERP repetition effects were more obvious at the left side for objects and at the right side for faces. ERP repetition effects were also larger for famous faces during this time-window. These later repetition effects may reflect deeper semantic processing and/or greater involvement of involuntary explicit retrieval processes for the famous faces. Taken together, these results suggest that among the implicit and explicit memory processes elicited by a perceptual priming task, some of them are modulated by the type of item which is repeated.