Gap detection in hearing-impaired chinchillas.

Auditory temporal resolution is known to deteriorate with sensorineural hearing loss; however, there is considerable intersubject variability in human studies. The purpose of the present study was to obtain measures of temporal resolution in the chinchilla as the degree of noise-induced hearing loss was systematically varied. Gap-detection thresholds, a measure of temporal resolution, were evaluated at four levels of noise-induced asymptotic threshold shift (ATS). Gap thresholds were normal when the pure-tone thresholds were elevated approximately 15 dB. With a hearing loss of approximately 30 dB, the gap thresholds were longer than normal if compared at the same sound pressure level, but within normal limits if compared at the same sensation level. When the hearing loss exceeded 40 dB, gap thresholds were longer than normal both in terms of sound pressure level and sensation level. These results show that there is an orderly breakdown in temporal resolution as the degree of noise-induced ATS increases. The results are related to neural data and models of temporal resolution.