Discrimination of brief tones by humans with temporal lobe damage

A number of recent Russian investigations [A. V. Baru and T. A. Karaseva, The Brain and Hearing, Consultants Bureau, New York, (1972)] reported that dogs and humans with large auditory cortex lesions, exhibit significant increases in both their absolute detection thresholds as well as their frequency difference limens for tonal signals which are shorter than 16 ms in duration. In contrast, more recent studies [J. L. Cranford, J. Acoust. Soc. Am. 65, 1573–1575 (1979)] with cats suggest that the cortex, rather than being essential for detecting the simple presence of brief tones, may be more important for discriminating qualitative differences in such sounds. While having normal absolute detection thresholds for brief tone pulses, cats with auditory cortex lesions, in comparison to unoperated controls, do exhibit elevated frequency difference limens. In order to investigate the inter‐species generality of these new animal findings, we recently presented the same series of brief tone tests to two human patients with temporal lobe lesions (one left‐sided CVA, and one right‐sided glioblastoma case). The results with the two patients are remarkably similar to those obtained with cats. Both patients exhibited normal absolute detection thresholds for brief tones in combination with significantly elevated frequency difference limens. [Work supported by Deafness Research Foundation and NINCDS.]