CORTICOCORTICAL CONNECTIONS OF THE SUPERIOR SURFACE OF THE TEMPORAL OPERCULUM IN THE MONKEY (MACACA MULATTA)

Abstract

Six monkeys were subjected to exposure of inferior bank of Sylvian fissure (and other sulci): strychnine placed on this bank caused spikes in the electroencephalogram which could be traced according to the methods of physiological neuronogra-phy. The acoustic receptive cortex lay on the posterior portion of the superior surface of the temporal operculum (supra-temporal plane or s-t.p.); it had strong projections to the upper part of the frontal eye field, the fronto-parietal face area, and the visual association areas, as well as to other portions of the temporal lobe. By way of the posterior fourth of the corpus callosum, the auditory receptive cortex has connections from one side to the similar cortex on the other side. The anterior, non-auditory regions of the s-t.p. lack the extensive efferent connections of the auditory cortex, but fire into neighboring regions. The cross-hemispheric connections run in the anterior portion of the middle of the corpus callosum. All parts of the auditory cortex fired into the peristriate cortex, but only the anterior and posterior segments fired as well into area 18 (parastriate cortex). The anterior and posterior walls of the lunate sulcus and the buried cortex of the annectant gyrus therein behave like area 18. The strong connections from the s-t.p. to the frontal cortex are chiefly into the buried cortex of the arcuate sulcus (area 8), but also into nearby areas.