SPATIAL MEMORY, HABITUATION, AND REACTIONS TO SPATIAL AND NONSPATIAL CHANGES IN RATS WITH SELECTIVE LESIONS OF THE HIPPOCAMPUS, THE ENTORHINAL CORTEX OR THE SUBICULUM

Various spatial memory deficits have been described in rats with damag e to the hippocampal formation (including the subiculum and the entorh inal cortex) and particularly in rats with selective lesions of the hi ppocampus proper. So far, the involvement of the entorhinal cortex in spatial memory is still controversial and the role of the subiculum is poorly documented. The aim of the present study was to compare the be havioural effects of selective lesions of the hippocampus, the entorhi nal cortex or the subiculum in (a) a water-maze task using testing pro cedures sensitive to the disruption of reference or working memory and (b) in an object exploration task designed to evaluate habituation an d subsequently reactions to changes of the spatial layout of objects ( spatial change) or to the substitution of a familiar object by a new o ne (nonspatial change). Our results showed several similarities betwee n the behavioural consequences of damage to each of the three structur es. A few differences were also noted. Hippocampal rats were impaired in all spatial tasks, but they reacted like controls to a nonspatial c hange. The rats sustaining lesions of the entorhinal cortex or the sub iculum were not impaired in the reference-memory procedure of the wate r-maze task and showed a deficit in reacting to a nonspatial change. O verall, our results confirm the central role of the hippocampus in spa tial memory and also suggest a role for the entorhinal cortex and the subiculum in processing spatial informations. in addition, they indica te that the entorhinal cortex and the subiculum may have a hippocampal -independent role in memory. (C) 1998 Elsevier Science B.V. All rights reserved.