PATTERNS OF HAIR CELL DAMAGE AFTER INTENSE AUDITORY STIMULATION

Guinea pigs were exposed to pure tones of 125, 500, 1000, 2000 and 4000 Hz at intensities of 130 and 150 dB SPL for a period of one or four hours. Each cochlea was prepared histologically using the “surface specimen technique,” and a cochleogram of the sensory cell population was constructed to show the pattern of hair cell loss. The radial distribution of damage was related to exposure frequency. Lower frequencies produced proportionally greater damage in distal hair cell rows than did higher frequencies. Hair cell damage caused by exposures at 150 dB was severe over wide areas, extending from the supposed site of maximum stimulation primarily toward the base. Exposures to 130 dB caused damage which was more selective than has been reported previously. Lesions produced by a 4000 Hz tone appeared near the stimulation maximum for that frequency, but lesions caused by lower frequencies tended to appear progressively nearer the base with respect to stimulation maxima. The existence of multiple peaks of damage was a prominent feature. Two mechanisms of damage appear necessary to interpret the damage patterns which were observed: 1) direct mechanical stress, which was most important at higher frequencies, and 2) gradually accumulating effects, which were most important at lower frequencies, and to which OHC were particularly susceptible. Particular attention was paid to the possible role of the ear's nonlinearity in accounting for discrepancies between hair cell damage patterns and patterns of normal hair cell stimulation. © 1969, SAGE Publications. All rights reserved.