Perirhinal and postrhinal cortices of the rat: a review of the neuroanatomical literature and comparison with findings from the monkey brain.

This review is prompted by recent findings that the perirhinal and parahippocampal cortices in the monkey brain are important components of the medial temporal lobe memory system. Given the potential importance of the comparable rcgions 1 0 niemory function in rhe rat brain, it is surprising that so little is known about their neuroanatomy. In fact, there are no comprehensive studies of the borders, cytoarchitecture, or connections of the cortical regions surrounding the posterior portion of the rhinal sulciis in the rat. This review is meant to summarize the current state of our knowledge regarding these regions in the rat brain. Based on existing data and our own observations, a new terminology is introduced that retains the term perirhinal cortex for the rostral portion of the region and renames the caudal portion the posirhi!,ind cortex. Issues of continuing uncertainty are highlighted, and information gleaned from the monkry literature is used to predict what anatomical traits thc rat perirhinal region might demonstrate upon further examination. To the extent possible with available data, the similarities and differences of the ra t and monkey perirhinal, postrhinal, and parahippocampal regions are evaluated.