Hippocampal Lesions and the Partial Reinforcement Effect

Abstract

Two hypotheses of hippocampal function predict that nonreinforcement effects should be attenuated in hippocampal-lesioned rats. As a test of these hypotheses, hippocampal-lesioned and normal rats were trained in the straight runway on continuous or partial reinforcement schedules and then extinguished. In acquisition, lesioned rats ran slower over-all than normals and slower on trials following reward than normals, but there was no difference on trials following nonreward. In extinction, although lesioned Ss with continuous reinforcement were more resistant to extinction than normals, there was little difference between lesioned and normal groups having partial reinforcement and no significant attenuation of the partial reinforcement effect. The results were interpreted as implicating the hippocampus in the mediation of reinforcement rather than nonreinforcement effects.