Effect of high-intensity sound on cochlear microphonics and activity of inferior colliculus neurons in the guinea pig.

The input-output functions of cochlear microphonics (recorded from the round window) in guinea pigs exposed briefly to high-intensity sound (2 kHz, 130 dB, 30 min) were shifted toward higher intensities by about 15 dB in comparison with normal animals. 2-4 h after the exposure this shift decreases to 10 dB. The response characteristics of the inferior colliculus neurons were compared under similar conditions. Thresholds at the characteristc frequencies (CF) measured 2-4 h after exposure, were raised by 30-50 dB, a higher threshold increase was observed at frequencies from 5-7 kHz. 48 h after exposure the thresholds approached those obtained in normal animals. There was no pronounced hair cell loss after exposure. It is assumed that in addition to the impairment of sound transduction in hair cells there may be a specific effect of high-intensity sound exposure on neuronal transmission in the auditory pathway.