CORTICAL ORGANIZATION IN GUSTATION (MACACA MULATTA)

Abstract

Pre- and postoperative detns. of acceptance threshold for quinine hydrochloride soln. were made in 6 immature monkeys. Surgical procedure consisted of ablation of the cortex of the anterior part of the Island of Reil, the operculum, and the anterior supratemporal plane. Three animals received extensive though incomplete ablations involving all these loci; 3 other monkeys received more restricted lesions limited to the anterior portion of the island, island plus supratemporal or, island plus opercular cortex, respectively. Only the more extensive ablations of opercular, island and supratemporal cortex resulted in ageusia. Some lowering of acceptance threshold, however, followed ablation of opercular plus island cortex, but no such lowering followed ablation restricted either to island or to island plus anterior supratemporal plane. These data, added to those obtained by Patton, can be made understandable by using an analogy to cerebral mechanisms in vision. As for vision, total incapacity results only from the most extensive involvement of the "primary" projection system. For gustation, therefore, it may be inferred that the "primary" cortical representation includes the cortex of the operculum, insula, and anterior supratemporal plane. As in vision, however, a cortical "macula" may be present. For gustation, this "macula" seems to be focused on the junction of the frontal operculum and the anterior insula. Continuing the analogy to vision, certain discrepancies in previous interpretations can be resolved. In vision, a dissociation of mechanisms of discrimination performance from those of "field" have been demonstrated. The former depend on the integrity of the inferior occipitotem-poral cortex, the latter on that of the "primary" projection (striate) cortex. In a similar manner a dissociation between dietary habits (food discrimination) and quinine acceptance threshold was established in gustation. Thus anteromedial temporal cortex appears to be implicated in gustatory discriminations; anterior sylvian (opercular, insular, and anterior supratemporal) cortex in more "primary" gustatory functions.