Forward masking recovery functions in auditory nerve fibers after noise exposure

Abstract

This research was prompted by psychophysical studies showing that the time constant for forward masking can be prolonged in listeners with sensorineural hearing loss [e.g., Cudahy, E., J. Acoust. Soc. Am. Suppl. 62, S59 (1976)]. The psychophysical results suggest that neural recovery might be prolonged at some stage within the auditory pathway, perhaps at the auditory nerve. In order to explore this issue, recordings were made from auditory nerve fibers in noise‐exposed chinchillas. Neural recovery functions were obtained by measuring a unit's responsiveness to a brief, low‐level probe tone which was preceded in time (2–200 ms) by an adaptor tone whose level was varied. The recovery functions from units in the noise‐exposed animals were generally similar to those in normal animals for adaptor tones 10–30 dB above threshold; however, some differences were noted at higher levels. These results will be compared to previous psychophysical and physiological results. [Work supported by NTH, NIOSH.]