Walter P. Covell

Factor Analysis of Cochlear Injuries and Changes in Electrophysiological Potentials Following Acoustic Trauma in the Guinea Pig

The changes in “threshold” and maximum responses for cochlear microphonic potentials and whole‐nerve action potentials were measured following acoustic trauma with 500‐cps tones. The cochlear‐microphonic responses were measured locally in the first turn of the cochlea for 500‐, 2000‐, and 8000‐cps test tones and locally in the third turn for a 500 cps test tone. The whole‐nerve action potentials were measured in response to 500‐ and 5000‐cps tone pips. Injury to the organ of Corti in the first and third turns was rated after examination of histological sections of the temporal bones. The physiological measurements, the injury ratings, and the sound pressures and durations of the traumatic exposures were examined together for correlations and analyzed for common factors. The results served primarily to confirm previous conclusions. For durations of exposure from 5 to 80 min, equal total acoustic energy in the exposure produced equal changes in the electrophysiological responses. The ratings of anatomical i...