MNEMONIC RESPONSES OF SINGLE UNITS RECORDED FROM MONKEY INFEROTEMPORAL CORTEX, ACCESSED VIA TRANSCOMMISSURAL VERSUS DIRECT PATHWAYS - A DISSOCIATION BETWEEN UNIT-ACTIVITY AND BEHAVIOR

Three macaques were trained on a task in which a sequence of single vi sual images was presented serially, and the monkeys signaled whether t he image was a new or a repeated one. The optic chiasm and splenium of the corpus callosum were transected, leaving the anterior commissure as the only path for cortical interhemispheric transfer, Images were p resented to only one eye at a time. Re-presentations of images to the same eye were recognized correctly in >95% of trials. A robust stimulu s-specific adaptation (i.e., a reduced response to a repeated image) w as seen in the population of single units recorded from inferotemporal cortex during these same trials. When an interhemispheric transfer wa s demanded of the animals (i.e., the re-presentation was made to the o ther eye), recognition performance was somewhat reduced, to 86% correc t. Interestingly, in this situation the stimulus-specific adaptation d isappeared completely, The disappearance occurred regardless of whethe r the transfer direction was from the hemisphere ipsilateral to the re cording site to the hemisphere contralateral to the recording site, or vice versa. Thus, stimulus-specific adaptation in inferotemporal cort ex units is not required for recognition.