Localization of Taste in the Thalamus of Macaca mulatta *

Traditionally the cortical representation of taste is described as overlapping or adjacent to the cortical olfactory area. Bornstein2 points out that present teaching with regard to the gustatory system is based not so much on an extensive and reliable body of experiment as upon the inference of an intimate anatomical as well as functional relation between taste and smell. The plausibility of this inference, together with the phenomenon of uncinate fits, has led the majority of writers to neglect scattered clinical and experimental observations to the contrary, and to locate the cortical taste area in the region of the uncus and hippocampal formation. On the basis of theoretical considerations as well as observations on man and monkeys, Bornstein2 has proposed a parietal opercular localization of taste: namely, that the taste representation occupies the foot of the postcentral gyrus, a region corresponding to Brodmann's area 43 in the human brain. The purpose of the present experiments is to demarcate the thalamic nuclei which relay taste impulses to the cerebral cortex. The locus of this relay and even the fact of the relay is an open question. Enough is known of the topographic organization of thalamocortical projection systems so that a demarcation of the thalamic nuclei for taste should bear upon the problem of cortical localization of taste. Conversely, Bornstein's hypothesis provides a definite point of attack, and makes unnecessary a random exploration of the thalamus which would 'be dictated by a purely empirical approach. It was predicted that discrete lesions placed in the thalamus of the monkey in the region of the nuclei which relay somatic sensation from the tongue would produce impairment of the sense of taste. According to the work of Walker"2 and of Le Gros Clark6 the arcuate nucleus projects