INTERHEMISPHERIC PROJECTIONS OF PARIETAL LOBE IN RHESUS MONKEY

The interhemispheric connections of various parts of the parietal lobe have been studied with silver impregnation technique in the rhesus monkey. The areas in SI representing the hand and foot did not project to the opposite hemisphere whereas face, trunk and limb girdles did so and their projections were directed to the homotopical and non-homotopical areas. These non-homotopical projections formed an arch posterior to the projection-free hand and foot area presumably representing the dorsal aspect of the body from face to occiput and from thoracolumbar to sacral segment of trunk. Area SI also projected to opposite SII in topographic fashion. In turn, area SII sent projection to opposite SII and, very little elsewhere. The remaining parts of parietal lobe, i.e., rostral part of the inferior parietal lobule and the dorsal and medial parts of the superior parietal lobule projected to homotopical and non-homotopical areas adjacent to it. In addition, these areas projected to parietal operculum (SII) in topographic fashion. By contrast, the caudal part of the inferior parietal lobule projected to entirely different non-homotopical areas besides projecting to the homotopical region. This area projected to the caudal part of insular cortex, the caudal part of cingulate gyrus, the parahippocampal gyrus and the superior temporal sulcus. Possible significance of these differential projections is discussed. © 1969.