Bilateral NMDA lesions centered on the postrhinal cortex have minimal effects on hippocampal place cell firing

The postrhinal cortex (POR) receives input from parietal cortex and sends output to the hippocampus. It may, therefore, relay spatial information to the hippocampus and as a result, lesions of POR may disturb the spatial firing patterns of hippocampal place cells. To test this hypothesis, the firing of hippocampal CA1 place cells in rats with bilateral N-methyl-D-aspartic acid lesions centered on the POR (n = 83 cells) and rats with sham lesions (n = 77 cells) was compared, while animals foraged freely. The main effect of postrhinal lesions on the basic firing properties of hippocampal place cells was to decrease the coherence of their firing fields. In contrast to the previously reported effects of lesions of neighboring perirhinal cortex, however, there was no effect of postrhinal lesions on the location stability of the fields over time or in the response of these cells to the animal's movement. These data indicate that information originating from the POR has relatively little influence on hippocampal place cell firing while an animal is engaged in foraging behavior. This also suggests that perirhinal and postrhinal cortices make distinct contributions to hippocampal functioning.