Physiological significance of sulci in somatic sensory cerebral cortex in mammals of the family procyonidae

On the basis of histological studies it has been generally accepted that certain cortical sulci, such as the central sulcus and the lunate sulcus in primates, reliably delimit one cytoarchitectonic region from another (Connolly, '50 ). There are many instances, however, where the cytoarchitecture is similar on both sides of a sulcus. This occurs, for example, within somatic sensory cortex of the raccoon. The lack of a clear cytoarchitectonic difference in such cases in no way argues against the delimiting character of these sulci, however, since adjacent gyri separated by a sulcus may be functionally distinct. Indeed, electrophysiological mapping studies in a variety of mammals have shown that sulci often lie between physiological distinct regions within and around somatic sensory cerebral cortex (Woolsey, '60). The primary purpose of the study reported below was that of specifically testing the hypothesis that neocortical sulci demarcate one type of physiological subdivision from another. By means of evoked potential mapping techniques this hypothesis was tested in a series of closely related carnivores that exhibit different neocortical fissure patterns. The results that were obtained confirmed this hypothesis for the sulci within and around the somatic sensory cerebral cortex in ten animals from five genera of the family Procyonidae. Further hypotheses pertaining to the underlying causes of fissure fonnation are discussed, and additional data are presented which indicate a correlation between certain aspects of behavioral expression and the differential enlargement of specific cortical somatic sensory subdivisions. METHOD