Damage to hippocampus and hippocampal connections: Effects on DRL and spontaneous alternation.

Abstract

Male albino rats were tested both pre- and postoperatively either on a schedule of differential reinforcement of low-rate responding (DRL 20 s, experiment 1) or for spontaneous alternation (experiment 2). Selective lesions were produced in the hippocampus and its fiber connections. Performance of both behaviors was consistently disrupted by total fornix, medial fornix and septum lesions, while neither behavior was significantly disrupted by postcommissural fornix or entorhinal cortex lesions. Anterior hippocampus lesions consistently disrupted only DRL performance, while neither posterior hippocampus nor lateral fornix lesions resulted in consistently impaired performance of either behavior. This may represent a possible functional differentiation between anterior and posterior portions of the hippocampal system.