Augmentation of latent inhibition by electrical stimulation of hippocampus

The effects of low-level hippocampal stimulation on the development of latent inhibition were investigated employing classical conditioning of the nictitating membrane response of rabbits. Four groups were given either (a) no preexposure of the to-be-CS, (b) preexposure, (c) preexposure overlapped by hippocampal stimulation or (d) preexposure overlapped by cortical stimulation, followed by 300 conditioning trials for each group. After conditioning, the hippocampal group was divided into two groups designated HS-1 and HS-2 by means of a post-hoc test for stimulation effects. Conditioning was found to be retarded in all three preexposed groups, with significantly greater retardation (augmentation of latent inhibition) in Group HS-2. The results support a general conception that the hippocampal stimulation produced its effects through the modulation of sensory input.