CONTRIBUTIONS OF THE HIPPOCAMPUS, AMYGDALA, AND DORSAL STRIATUM TO THE RESPONSE ELICITED BY REWARD REDUCTION

Rats were trained to run down a runway for either 1 or 10 food pellets . After training, those receiving 10 pellets were shifted to 1 pellet. Such shifts typically elicit a temporary decrease in running speed. G roups of normal rats and rats with bilateral lesions of the fimbria-fo rnix, lateral-basolateral complex of the amygdala, or dorsal striatum were tested with the shifted and unshifted procedures. Separate experi ments, identical except for the intertrial intervals (ITIs; 3 min vs. 30 s), were carried out. The data are consistent with the view that an integrated action of multiple neural systems is required to observe t he typical response to reward reduction in unlesioned rats. One system that includes the dorsal striatum promotes a reinforced approach resp onse to the goal box. A neural system that includes fimbria-fornix is required to retain information about reduced reward over the 3-min ITI . A system that includes the amygdala may acquire a conditioned aversi ve response to the goal box after the shift is detected, leading to re duced speeds over testing.