The role of the amygdala in conditioned flavor preference.

Long-Evans rats with control or amygdala lesions were tested in a conditioned flavor preference task. Half of the rats in each lesion group received an unsweetened grape-flavored solution on odd-numbered days and a sweetened cherry-flavored solution on even-numbered days. The remaining rats received a sweetened grape-flavored solution on odd-numbered days and an unsweetened cherry-flavored solution on even-numbered days. The appropriate solution was presented once a day for 15 min to each rat in the homecage. After six days of testing, each rat received unsweetened cherry and grape flavored solutions simultaneously for 15 min daily across four days. When the two unsweetened flavored solutions were presented simultaneously control rats showed a significant preference for the flavor that was sweetened during training compared to the unsweetened solution. However, amygdala-lesioned rats did not show a preference. The data suggest that the amygdala may be critically involved in mediating reward-based conditioned flavor preference.