Auditory Intensity Discrimination in Patients with Temporal-Lobe Damage

Abstract

This experiment was designed to permit evaluation of the effect of temporal-lobe damage on auditory intensity discrimination. The intensitive difference limen for a tone of 2,000 cps was obtained for three intensity levels under monaural and binaural conditions of testing. The results for 45 temporal-lobe patients were grouped according to the side of the excision, the extent of removal of the transverse gyri of Heschl and the time of testing (before or after operation). Thirteen hospitalized control patients were tested and then retested after an appropriate interval for inclusion with the pre- and post-operative data. Statistical analyses of the pre- and post-operative data were performed separately because not all patients were tested both before and after operation. The major findings were: 1) Before operation, there was no significant difference among groups in ability to discriminate changes in intensity. 2) After operation, there was a significant difference among groups in ability to discriminate changes in intensity. 3) Specifically, the group of patients with left temporal-lobe excisions including the transverse gyri of Heschl was hypersensitive to intensity change after operation as compared with each of the other groups. The results indicate that the two temporal lobes in man are not equally concerned with intensity discrimination and suggest further that the transverse gyri of Heschl in the left temporal lobe may be an important component of a descending auditory system.