The role of the agranular insular cortex in anticipation of reward contrast.

Sixteen male Long-Evans rats were tested on a modified version of Flaherty et al.'s [Flaherty, C. F., Turovsky, J., & Krauss, K. L. (1994). Relative hedonic value modulates anticipatory contrast. Physiology and Behavior, 55, 1047-1054.] anticipatory contrast paradigm to assess memory for the anticipation of reward. Prior to testing each rat received either a control or quinolinic acid induced lesion of the agranular insular cortex. In the home cage, each rat was allowed to drink a water solution containing 2% sucrose for 3 min followed by a water solution containing 32% sucrose for 3 min. Across 10 days of testing, the control rats showed significantly increased anticipatory discriminability as a function of days. In contrast, rats with agranular insular cortex lesions failed to show anticipatory discriminability. The results of a preference task revealed that both groups could perceptually discriminate between a 2% and a 32% sucrose solution. The data suggest that the agranular insular cortex may be involved in the anticipation of reward.