Detection v discrimination of brief-duration tones. Findings in patients with temporal lobe damage.

Based on earlier experiments with cats, we have developed two new hearing tests to evaluate the ability of patients with temporal lobe damage to discriminate tones of short temporal duration. Earlier published studies suggested that patients exhibit notably increased thresholds for detecting tone pulses shorter than 200 ms in length when the signals are presented to the ear located contralateral to the damaged hemisphere. Our experiments with cats indicated that auditory cortex lesions had no effect on the cats' ability to detect brief tones but did impair their ability to discriminate small changes in the frequency of such signals. In giving the brief-tone tests to seven patients with temporal lobe damage, we found a similar behavioral dissociation. All patients exhibited normal detection thresholds in conjunction with substantially elevated frequency difference limina.