ACTIVITY OF PRIMATE INFEROTEMPORAL NEURONS RELATED TO A SOUGHT TARGETIN PAIR-ASSOCIATION TASK

Visual long-term memory in primates has been assessed by using the pai r-association (PA) task, in which a subject retrieves and chooses the paired associate of a cue picture, Our previous studies on single neur ons in the anterior inferotemporal (AIT) cortex suggested their roles in representing paired associates in the mind, To test the possibility that the delay activity of AIT neurons is related to a particular pic ture as a sought target, we devised the PA with color switch (PACS) ta sk. In the PACS task, the necessity for memory retrieval and its initi ation time were controlled by a color switch in the middle of the dela y period, A control task, in which there is no color switch, correspon ds to the conventional delayed matching-to-sample (DMS) task where the monkey chooses the same picture as a cue, We found that AIT neurons s tarted to respond just after the color switch in the PACS task, when t he cue-optimal picture's associate was presented as a cue, In contrast , they showed no response change in the DMS task, We confirmed that th is effect is not due to the visual response to colors. Furthermore, wh en the cue-optimal picture was presented as a cue, these neurons showe d suppression after the color switch in the PACS task, These results s uggest that the activity of AIT neurons mediates gating mechanisms tha t preferentially pass information about a sought target, even when the sought target is retrieved from long term memory.