title: Origin of the pyramidal tract determined with horseradish peroxidase.
abstract: The origin of the axons contained in the pyramidal tract (PT) of the cat was established using retrograde transport of horseradish peroxidase (HRP). A complete section was made through a PT at the level of the medulla oblongata and HRP was applied to the sectioned axons. Cat brains were cut in frontal and sagittal planes and HRP-labeled cells were plotted in outlines of the brain sections. The entire cortical region containing PT cells was divided into 8 subregions and the percent of PT cells was determined in each. Surface cortex, subregions 1, 3 and 8, contained only 30--40% of PT cells; the majority resided in deep sulcal cortex, in subregions 2, 4, 5, 6 and 7. Subregion 1 (containing 6--12% of PT cells) extends rostral to the cruciate sulcus; subregion 3 (15--22%) extends from the cruciate sulcus caudally to the ansate sulcus; subregion 8 (7--8%) covers cortex laterally adjacent to subregion 3. The hidden banks of the cruciate sulcus contained the greatest concentration of PT cells, 28--34% in the dorsal bank (subregion 5) and 15--20% in the ventral bank (subregion 4). The coronal sulcus contained only 2--5% of PT cells in its dorsal bank (subregion 6) and 1--4% in its ventral bank (subregion 7). The presylvian sulcus contained 8--12% of all PT cells in its lateral bank (subregion 2). This new cortical area is not yet considered part of 'PT cortex'. Qualitative limitations of this study are discussed.
mesh_terms: D000818:Animals; D001369:Axons / Q000648:ultrastructure; D002415:Cats; D002540:Cerebral Cortex / Q000033:anatomy & histology; D002642:Chick Embryo; D004285:Dogs; D006735:Horseradish Peroxidase; D008526:Medulla Oblongata / Q000033:anatomy & histology; D009474:Neurons / Q000648:ultrastructure; D011712:Pyramidal Tracts / Q000033:anatomy & histology*
chemical_list: D006735:Horseradish Peroxidase