Auditory temporal integration in the normal-hearing and hearing-impaired cat.

Temporal integration functions obtained from human subjects with sensorineural hearing loss have shallower slopes than the functions obtained from normal-hearing subjects. The present investigation was designed to explore this relation in animals in order to compare normal-hearing cats and humans. Auditory temporal integration functions were measured for five cats before and after they were exposed to a 2-kHz tone at 110 dB SPL for 48 h. To measure the temporal integration functions, ten stimuli were used that had overall durations from 8.32 to 275 ms and that were configured either as single or multiple tone bursts of 6.25 kHz. Twelve thresholds for each stimulus were obtained from each animal before and after the sound exposure. Pre- and postexposure audiograms were also obtained and the mean permanent threshold shift at 6.25 kHz was 32.5 dB. Exponential and power function models were used to describe the data. The exponential model (with grand-mean data) yielded a pre-exposure time constant (tau) of 188 ms [mean absolute residual (MAR) of 1.5 dB] and a postexposure tau of 21 ms (MAR of 1.4 dB). For the power function model with grand-mean data, the pre-exposure slope was 6.6 dB per decade of duration (MAR of 1.4 dB) and a postexposure slope of 3.8 dB per decade of duration (MAR of 0.7 dB). The results indicated that the slope of the temporal integration function was less steep after sensorineural hearing loss of cochlear origin, and that the power function model was more effective in describing temporal integration data for the range of stimulus durations employed.(ABSTRACT TRUNCATED AT 250 WORDS)