Involvement of the lateral and dorsolateral amygdala in conditioned stimulus modality dependent two-way avoidance performance in rats

Abstract

Post-lesion learning and performance of shuttle-box avoidance and subsequent transfer to two warning signals (CSs) of different modality were investigated in 27 rats subjected either to a sham lesion (Group NORM), electrolytic injuries of the lateral amygdaloid nucleus (Group LAT), or combined lesions of the amygdalostriatal transition area and dorsolateral amygdala (Group D-LAT). All groups were divided into two subgroups according to warning signal sequences. In the first subgroup (D-DN-N sequence) the subjects were initially trained with the visual CS (darkness - D), then transferred to the more salient visual and auditory compound CS (darkness and noise – DN), and finally to the auditory CS alone (noise – N). The opposite arrangement of the CSs (N-ND-D sequence) was employed in the second subgroup. A small interference with shuttle-box learning, and no transfer deficit were seen in Group LAT, whereas D- LAT rats showed dramatically slow and inconsistent acquisition of avoidance responding followed by rapid weakening of performance during the training. In contrast to controls, in both lesioned groups avoidance and intertrial responding (ITR) were independent of the CS modality changes. The results indicate differential involvement of the lateral, and also of the dorsolateral amygdala, and amygdalostriatal transition area in CS processing, as well as in the mechanisms related to consolidation of the associations created during avoidance training.