Activity of Dentate Gyrus During NM Conditioning in Rabbit

Summary

Two studies were conducted to characterize the role of dentate gyrus during classical conditioning of the rabbit nictitating membrane response. In the first study, dentate field potentials elicited by perforant path stimulation were recorded before and during training to test for changes in granule cell excitability. Results showed above-baseline increases in population spike amplitude over the course of training in paired but not unpaired animals. In a second study, the activity of identified single granule cells was recorded during conditioning to determine if they exhibited the same neuronal response patterns seen in hippocampal pyramidal cells and in entorhinal cortex. Unlike responses in these other areas, granule cell responses did not develop a model of the behavioral response; instead they were tied more to stimulus presentation, with many cells exhibiting stimulus-evoked thetafrequency bursting in paired but not in unpaired animals. Taken together these studies suggest an intimate involvement of the dentate gyrus in the associative process; however dentate’s role appears to be different from that of other hippocampal regions.