Object exploration and reactions to spatial and nonspatial changes in dentate gyrus lesioned rats.

In order to investigate the possible involvement the DG in spatial and object recognition memory, we have opted for a non-associative task where no explicit reward was present. Colchicine was used for bilateral DG lesions for its well-known specificity for DG lesion. Colchicine-induced lesions produce severe damage in the granule cells of DG, while minimally affecting pyramidal cells in CA1 and CA3. The main results are as follows: The overall habituation to the familiar environment in DG lesioned rats was decreased than in sham operated rats. There was no significant impairment in detecting spatial novelty. Lesions of the DG did not affect the detection of a novel object placed in a familiar location. Considering both the impaired habituation and the generally intact detection of spatial changes, we suggest that exploratory activity in relation to the entire environment and to the particular objects is thought to be subserved by diverse nervous substrate, and testing in the given conditions allows for their differential estimation.