Event related potentials during object recognition tasks.

In our previous studies, we have demonstrated an ERP correlate of visual memory with a modified delayed matching-to-sample paradigm using a series of nonsense line drawings or faces as stimuli. In this experiment, we employed pictures of objects to determine whether the ERP can reflect the object recognition process and whether visual stimuli with a verbal label would result in a different topographic distribution from past topography obtained with visual stimuli without a verbal label. The results of this study suggest that the amplitude of the ERP component (c247) to repeated (primed) pictures of common objects was significantly decreased as compared to the unrepeated (unprimed) pictures; the latency for the peak of c247 was decreased for the repeated compared to the unrepeated, and the response time was also significantly shorter to the repeated picture stimuli than to the unrepeated; the topographical distribution of c247 was mainly located in the occipitotemporal areas of the brain. However, the source energy density map showed that the topographic involvement of the brain regions to the c247 was different in the matching and nonmatching trials.