Central localization of gustatory perception: An experimental study

There appears to be rather general agreement as to the structure of the peripheral endings involved, as well as the course and the anatomical variations to be found in the root fibers of the VII, IX, and X cranial nerves which carry impulses set up by gustatory stimuli, The fibers of these gus-tatory components on entering the brain separate from the other components of the respective nerves to become associated with the fasciculus solitarius and to terminate in its associated gray, the dorsal visceral gray. There is considerable evidence that, from this dorsal visceral gray, there is a discharge forward over bundles accompanying the medial lemniscus to the con-tralateral hypothalamus and dorsal thal-amus (Allen, '23a, '23b; Walker, '38). Those fibers passing to the hypothalamus separate from the medial lemniscus at midbrain levels to proceed to their destination by way of the mammillary peduncle. The possibility of a discharge to the homo-lateral thalamus and hypothalamus has never been proved or disproved. Less information exists with regard to the thalamic and cortical centers concerned with taste. The uncertainty as to the location of cortical centers for gusta-tory impulses may be explained on the basis of: (1) the difficulty involved in accurate experimental and clinical testing for taste; and (2) the infrequency of clinical conditions in which a central lesion involving taste is seen at a time when selective testing is possible. The following experimental study was undertaken in an attempt to explore further the thalamic and cortical centers for gustatory sensation. '28; Marcus, '34) have concluded that all the cortical areas concerned with representation for gustatory sensation are in close relationship to the cortical olfactory areas. Bornstein ('40a) discussed three possibilities of gustatory cortical localiza-tion: e.g., that the centers are in the temporal lobe, the insula, or the parietal oper-culum. He felt that the functional relation taste bears to tactile sensation predicates a convergence of these two kinds of sensation in the cortex rather than one of gus-tatory and olfactory sensations. He, therefore , favored the parietal operculum as the probable location for cortical representation. In a subsequent report, Bornstein ('40b) described a technique for semi-quantitative testing of taste and presented the case histories of three patients who had suffered bullet wounds of the parietal bone which produced lesions of the pre-and the post-central gyri of the left hemisphere. Testing, which was done four to six years after the accident, revealed changes …