Cytoarchitecture of the canine perirhinal and postrhinal cortex.

The perirhinal cortex in the dog's brain is composed of two traditional Brodmann's areas: 35 and 36. Area 35 is situated along the entire rostro-caudal extent of the fundus of the posterior rhinal sulcus, whereas area 36 occupies its lateral bank. In this study, four subdivisions were distinguished in area 35 based on cytoarchitectonic differentiation. Area 36 is poorly developed in the dog's brain and was divided into two subdivisions. The most characteristic features of area 35 are: a wide layer I, scattered cell clusters in layer II, and a prominent layer V containing a distinct population of large multiform neurons. Area 36 can be recognized by the presence of numerous cell clusters in layer II and increasing radial arrangement of neurons in deep layers of the area. Two fields of the postrhinal cortex were identified in the additional postrhinal gyrus, which is found in the fundus of the most caudal extent of the posterior rhinal sulcus.