Cytoarchitectonic study of the cerebral cortex in the horse brain--classification of the cortex area

A cytoarchitectural classification of the horse cerebral cortex was done to determine whether functional locations exist or not such as found in the human cerebral cortex. Two adult horse brains were examined by Nissl and myelin stained methods. Six cell layers of the cerebral cortex were identified and classified into five types areas based on the cytoarchitectural organization: agranular, frontal, parietal, polar and granulous types. The agranular type was seen around the gyrus sylvius. In layer V of the agranular type, there were the many large cells that seemed like Betz cells. This type was recognized as motor area. The frontal type was seen in the lower and parietal parts of the cortex. The parietal type was seen in the rostral and occipital lobes. The polar type was seen in the frontal and dorsal-occipital sides. The granulous type was seen in the anterior-lower and posterior-lateral part of the cortex. The occupational ratios of the five types, that is, agranular, frontal, parietal, polar and granulous, to the whole cerebral cortex, were calculated by three-dimensional analysis using computer system as 19.6, 27.0, 28.9, 13.6 and 10.9%, respectively. As a result of myelin stain, horizontal fibers were seen in layer IV of parietal and polar types which looked liked the line of Gennari, therefore this area was recognized as the primary visual area.