Autonomic-somatic relationships in the rabbit (Oryctolagus cuniculus): Effects of hippocampal lesions

Abstract

Rabbits received sham, cortical control, or dorsal hippocampal lesions and were subjected to simple Pavlovian conditioning. Eyeblink (EB), electromyographic (EMG), and heart rate (HR) CRs were assessed. Shock thresholds, HR URs, and free-field activity were also measured in selected animals. The acquisition of the EB and EMG CRs was not impaired in hippocampal lesioned animals, although hippocampal lesioned animals revealed impaired extinction performance on these measures. The magnitude of the HR CR was enhanced in hippocampectomized animals relative to control animals. Free-field activity was also greater in hippocampal lesioned animals, but shock thresholds and HR URs were unaffected by hippocampectomy. These findings suggest that “orienting” mechanisms may be impaired in hippocampal lesioned animals, resulting in an enhanced visceromotor response to stimulation which, under certain conditions, may affect somatomotor behaviors.