Abstract
Last year, we presented that single neurons in anterior insular cortex of rhesus monkey responded during multi-trial reward schedule task. In the task monkeys were required to complete 1, 2, 3 or 4 red-green visual discriminations to obtain a juice reward. These schedules were randomly picked. In cued condition, a visual cue was presented in each trial, with the brightness of the cue indicating how many trials remaining before the rewarded trial. In shuffled condition, the order of cue brightness was shuffled within each schedule, making the relation between the cue and reward probabilistic.344/510 (67%) anterior insular neurons responded during the task. 166 were tested in both conditions. Anterior insular neurons tended to respond near the end of schedules (63/166 responded only during the rewarded trial in cued condition), and near the end of those trials. 72/166 responses preceded the rewarding event, suggesting reward expectancy signals. In shuffled condition, 6/166 showed graded modulation, which might have the relation with the reward predictability in the task schedule.These results suggest that the single neuronal responses in insular cortex are related to impending reward, and some responses are involved in estimation of reward availability when the rewarding sequence is not indicated to monkeys. [Jpn J Physiol 54 Suppl:S189 (2004)]
