Changes in frequency selectivity in the chinchilla following a noise induced permanent threshold shift.
Davis RI; Ahroon WA; Hammernik RP
J Acoust Soc Am 1988 Mar; 83(Suppl 1):S116
Evoked-potential tuning curves (TC) were obtained on 106 chinchillas before and after acoustic overstimulation in order to assess the effects of the magnitude of hearing loss on frequency selectivity. Pre- and post exposure measures of auditory thresholds and masked thresholds (simultaneous tone-on-tone paradigm) were obtained in each animal at 0.5, 1, 2, 4, 8, and 11.2 kHz, using the evoked auditory response recorded from the inferior colliculus. Three TC variables (Q-10 dB, tail-tip difference, and the high-frequency slope) and sensory cell losses were compared to the amount of noise-induced permanent threshold shift (PTS) produced by a variety of noise exposures. Based upon large sample averages, frequencies showing PTS<20 dB also showed statistically significant differences between pre- and postexposure measures of all three TC variables. For 10 < PTS < 20 dB only the tail-tip difference showed a statistically significant change, while for PTS < 10 dB there were no measurable changes in the TC variables. The percentage of outer hair cell loss showed an orderly and systematic increase as PTS increased and as TC variables changed across the entire range of test frequencies. The inner hair cells were essentially unaffected. These results show that there is a systematic change in the TC variables that define the quality of tuning as hearing loss progressively increases and that these changes are clearly related to outer hair cell losses.
Industrial-noise; Noise; Noise-exposure; Noise-frequencies; Environmental-exposure; Exposure-levels; Audiofrequency; Sound; Environmental-exposure; Environmental-hazards; Hazards; Sensory-thresholds; Models; Acoustics; Acoustic-signals; Animals; Laboratory-animals; Hearing-loss; Hearing; Vibration; Vibration-effects; Vibration-exposure; Cellular-function; Cellular-reactions; Cell-function
Journal of the Acoustical Society of America
Plattsburgh State University, New York