Dissociable effects of lesions to the perirhinal cortex and the postrhinal cortex on memory for context and objects in rats.

Memory for the context in which an object appeared was investigated with a version of the spontaneous object recognition paradigm. Sham-operated rats explore familiar objects appearing in incongruent but familiar contexts more than those appearing in congruent contexts, revealing memory for the context in which an object previously appeared. At short delays, perirhinal cortex-lesioned rats were unimpaired on memory for object in context, whereas fornix-lesioned rats showed only a mild impairment. In contrast, postrhinal lesions resulted in severe deficits. However, in a comparable noncontextual object task, postrhinal and fornix lesions had no effect, whereas perirhinal-lesioned rats were severely impaired. Comparison of these tasks and other published data may shed light on the nature of the contextual processing involved.