Parallel input to the hippocampal memory system through peri- and postrhinal cortices.

In the rat, the rhinal cortices consist of the perirhinal, postrhinal and entorhinal cortices. The perirhinal and postrhinal cortices, which serve as major input sources to the entorhinal cortex, receive functionally different types of information. In this study we looked at the projections from the perirhinal and postrhinal cortices to the different parts of the entorhinal cortices using an anterograde tracing technique. Our results show that the perirhinal cortex preferentially projects to the lateral entorhinal cortex, whereas the postrhinal cortex mainly sends fibers to the medial entorhinal cortex. Since the lateral and medial entorhinal cortices are differentially connected with the hippocampus, we suggest that functionally different types of information are processed in parallel in the hippocampal memory system.