INTRA-HEMISPHERIC AND INTERHEMISPHERIC CONNECTIONS OF NEOCORTICAL AUDITORY SYSTEM IN RHESUS MONKEY

The intra- and interhemispheric neocortical connections of various parts of the superior temporal gyrus and the supratemporal plane have been studied with the Nauta silver impregnation technique in the rhesus monkey. It has been found that the primary auditory area (TC) projects to its immediate association areas (TA and TB) ipsilaterally while it projects via the corpus callosum to the lateral part of area TC of the opposite side. The auditory association areas can be divided into rostral and caudal parts on the basis of their cortical connection patterns. The caudal part projects to parts of the prefrontal and premotor areas of the frontal lobe, parietal lobe and cingulate gyrus. The rostral part projects primarily to part of prefrontal lobe. The caudal part has interhemispheric projection via the corpus callosum whereas the rostral part has connections mainly via the anterior commissure. An analogy is made between the auditory and other neocortical sensory systems. The significance of 'midline' in auditory system is discussed. © 1969.