Small effect of upcoming reward outcomes on visual cue-related neuronal activity in macaque area TE during...

Area TE sends dense projections to the perirhinal cortex in macaque monkeys, an area in which we previously observed flexible signals regarding upcoming reward outcomes during a conditional-association cued-reward task. To investigate neuronal processing during the generation of information on upcoming reward outcomes, neuronal activities in area TE were examined. In the task, a color stimulus as Cue 1 and a pattern stimulus as Cue 2 were sequentially presented. Each pattern stimulus indicated both rewarded and unrewarded outcomes depending on the preceding color stimulus. In the activities during Cue 2 presentation, two-way analysis of variance revealed the effect of the interaction between Cue 1 and Cue 2, i.e., reward conditions, in 19 out of 133 neurons recorded in area TE. Of the 19 neurons, 12 also represented a response delineating a specific cue sequence, i.e., a trial-type activity. The latency of the reward-condition dependence in 7 neurons without the trial-type activity was indistinguishable from the latency in neurons without a trial-type activity in the perirhinal cortex. These results suggest that the effect of upcoming reward conditions is small in area TE and that the representation of reward conditions arises in areas beyond the ventral visual pathway, including the perirhinal cortex, during conditional associations.