Effects of intense pure tone stimuli when magnitude of initial injury is controlled.

Publisher Website
Google Scholar
Abstract
Guinea pigs were subjected to over-stimulation from either a 300-cycle or a 5000-cycle tone for a period long enough to produce a 60-decibel loss in sensitivity for the stimulating tone. Cochlear potentials were taken prior to stimulation, immediately following, and after a lapse of 3 weeks. The ears were also studied histologically. Individual variability in susceptibility to trauma is reduced under these conditions of stimulation. Test-retest measurement of cochlear potentials in the guinea pig is feasible. The acute results show that for a 300-cycle stimulus all tones up to 5000 cycles are affected to the same degree. The highest tones tested are more seriously impaired. For a 5000- cycle tone the entire audiogram suffers an approx. equal loss. After 3 weeks some recovery of function takes place in all of the 5000-cycle ears. Two of the group returned to normal levels. The 300-cycle injury is much more permanent. It appears that at equal sound pressures a low-tone stimulus is much more effective in producing injury than a high tone stimulus. Cochlear injury for a 5000-cycle stimulus is generally more restricted than for a stimulus of 300 cycles. For the cases reported here there exists a rank-order correlation of approx. 0.9 between the avg. loss in the electrical audio-gram and the percentage of cochlear structures destroyed. Results were discussed with reference to a place principle in the cochlea and interpreted to be generally unfavorable to such a principle.
Keywords