Repetition related ERP effects in a visual object target detection task

ERP responses to initial and repeated presentations of possible and impossi ble objects were recorded from 61 recording sites in a simple target detect ion task. In Experiment 1, the non-target objects were line drawings of pos sible and impossible 3-D geometric figures and the targets were line drawin gs of familiar everyday objects or combinations of parts of everyday object s. In Experiment 2, the non-target objects were everyday objects and the ta rgets were possible and impossible 3-D geometric figures. In both experimen ts, at frontal sites, the repeated possible and impossible non-target items elicited less negative ERP waveforms relative to first presentations betwe en 250 and 350-400 ms. At parieto-occipital sites, in both experiments, the repeated possible and impossible non-target items elicited less positive E RP waveforms than did first presentations beginning at about 300 ms. The br iefly reduced frontal negativity to repeated items is consistent with famil iarity arising from a facilitation of access to conceptual, semantic and vi suo-spatial representations during object categorization. The polarity of t he parieto-occipital effect was the reverse of what is usually found in sti mulus repetition tasks, although it is consistent with earlier work using s imilar visual stimuli. It is interpreted as reflecting the availability of a newly formed representation (i.e,, token) of the object just experienced. (C) 2001 Elsevier Science B.V. All rights reserved.