Increased responsivity of dentate granule cells during nictitating membrane response conditioning in rabbit.

We examined the responsivity of dentate gyrus granule cells to perforant path stimulation during classical conditioning of the rabbit nictitating membrane response. Dentate field potentials elicited by perforant path stimulation were recorded during training to test for changes in granule cell responsivity. Results showed above-baseline increases in dentate population spike amplitudes over the course of training in paired but not unpaired animals. In addition, population spike amplitudes were smaller when elicited during tone presentations in both paired and unpaired animals than between trials when no conditioning stimuli were present. While alternative interpretations remain, these results provide preliminary evidence that processes similar to long-term potentiation may occur in the hippocampus during behavioral conditioning.