MEMORY FOR SPATIAL LOCATION - FUNCTIONAL DISSOCIATION OF ENTORHINAL CORTEX AND HIPPOCAMPUS

To test whether there is a functional dissociation between the hippoca mpus and entorhinal cortex, rats were trained on a variable spatial-lo cation matching-to-sample (working memory) task with various delays. A fter training, rats with entorhinal cortex, entorhinal-cortex-plus-hip pocampus/subiculum, hippocampus, control, or cortical control lesions were tested for performance within the task. Results indicated that in the variable spatial-location condition relative to the control and c ortical controls, all lesioned groups showed a profound impairment in performance of the task across all delays. They were subsequently test ed for acquisition of a constant spatial location task. In the constan t spatial-location condition, the entorhinal cortex and entorhinal-cor tex-plus-hippocampus/ subiculum lesioned groups did not learn the task , whereas the hippocampal lesioned group did. It is suggested that the re is a functional dissociation between the hippocampus and the entorh inal cortex. It is proposed that the hippocampus encodes new spatial i nformation within a working-memory system, whereas the entorhinal cort ex represents spatial information within a reference-memory system as part of a spatial cognitive map.