Stimulus specific adaptation in excited but not in inhibited cells in inferotemporal cortex of macaque.

Many cells in inferotemporal cortex respond more actively to a novel presentation than to a subsequent re-presentation of the same image, exhibiting stimulus specific adaptation (SSA). Previously, analysis of this adaptation was limited to visually excited cells, excluding visually inhibited cells. In the present experiment we studied 654 cells in four macaques performing visual tasks. Strong SSA (P < 0.0001) was observed in those cells which were excited by visual stimuli. This adaptation was also seen in the subset of such cells which, though excited by visual stimuli, failed to show visual specificity in their responses. Interestingly, no SSA (P > 0.1) was observed in the group of cells inhibited by visual stimuli. Furthermore, most inhibited cells failed to show visual specificity. This lack of visual specificity and SSA suggests that the visually inhibited cells have a limited role in the detailed information processing of visual perception and memory activated by the tasks used in the present experiments.