Hippocampal substrate of sensory associations.

The role of the hippocampus in the association of two conditional stimuli was evaluated using the conditioned rabbit NM preparation and a sensory preconditioning paradigm. Multiple-unit activity was recorded from field CA1 during preconditioning. Paired presentations of CS1 and CS2 resulted in increased excitability which was highly correlated with later performance during CS2 test sessions. Unpaired presentations evoked a response to stimulus onset often followed by an inhibitory period. Bilateral kainic acid lesions of CA1 had no deleterious effect on traditional CS-US conditioning but abolished the association of CS1 and CS2. These data suggest that the hippocampus may be vital to the association of sensory events. Further, the SPC paradigm could provide an excellent model for evaluating simple cognitive deficits.