Detection versus discrimination of brief tones by cats with auditory cortex lesions

In recent years, a number of investigators have provided evidence that the auditory cortex has a critical role in both the detection and discrimination of brief sounds. Dogs and humans with lesions of the neocortical auditory centers have been reported to exhibit significantly elevated detection thresholds for signals shorter than 16 ms in duration. In tests of frequency discrimination, the same subjects also exhibited severe deficits whenever tonal signals were less than 20--40 mn in lengths. In the present report, we present evidence brief tones. Operated cats, while exhibiting normal difference limens for 1-kHz tones of 100-ms duration, have significantly elevated limens for discriminating tones of 8- and 2-ms duration. With further testing, the same operated cats can be shown to have normal absolute thresholds for detecting brief tones.