Incidental information acquired by the amygdala during acquisition of a stimulus-response habit task.

In the present paper we tested the hypothesis that the amygdala incidentally acquires information during the acquisition of a task sensitive to damage to the dorso-lateral striatum. Two groups of rats were trained on a stimulus-response (S-R) habit task on the eight-arm radial maze. Prior to initial acquisition, one group received NMDA lesions of the amygdala and the other received sham surgeries. After reaching a strict learning criterion, both groups underwent reversal training in either the same or different context from original training. Consistent with our previous work, the sham group showed enhanced reversal learning in a context different from original training. The rats with amygdala damage showed a deficit in reversal learning in both contexts, although the deficit was more apparent in the different context. Both groups of rats that underwent reversal training in the context different from original training showed a normal competition effect for this task (chance performance) when they were returned to the initial training context. This data supports the idea that the second S-R association, acquired during reversal training, and the context-specific inhibitory association, acquired during original training, were unaffected by the amygdala damage. Taken together, this pattern of data suggests that the amygdala incidentally acquired information during the acquisition of the S-R habit task. The nature of the association acquired in this learning paradigm, and the implications of this finding for theories dealing with the organization and functions of mammalian learning and memory are discussed.