Corticocortical connections of the angular gyrus and its adjacent areas

Abstract

The present paper deals with crticocortical connections of the posterior association cortex in cats, monkeys and man with particular empha sis on the most “developed” cortical region ; particularly the angular gyrus in man. Organization patterns of association fibers to the posterior association area are basically identical on several points in cats and monkeys. Thus, for example, convergence of association fibers from the somatosensory, auditory and visual cortical areas to a certain region in the posterior association area ( MSs, middle suprasylvian sulcus area in cat; STs, superior temporal sulcus area in monkey) is evident in both animal species. However, several dissimilarities, reflecting evolutionary development from carnivores to primates, do exist within the formation of some long association bundles, which have been revealed from a comparison of the findings obtained from the two kinds of animals. The angular gyrus (area 39) together with its adjacent areas can be considered from the evolutionary point of view as being homologue of part of the MSs and STs in the cat and monkey, respectively. Some aspects of the angular gyrus are discussed with relation to the monkey and crossmodal association (Geschwind, 1965), and the possibility of cortical connections between the angular gyrus and Broca's area is also commented with reference to our new findings obtained with the HRP method in monkeys.