Frequency spectra and gender differences

Includes bibliographical references (pages [32]-38)Nightly, 12-hour exposure to an augmented acoustic environment (AAE) consisting of a 70 dB SPL broadband noise slows hearing loss in DBA/2J (DBA) mice and other strains of mice that exhibit progressive sensorineural cochlear pathology. The AAE used thus far contains a broad range of frequencies stimulating much of the cochlea. To investigate the effects of stimulating a more restricted region of the cochlea, DBA/2J mice were exposed to either a high-pass (>15 kHz) or low-pass (< 10 kHz) filtered noise (70 dB SPL, 200 ms duration, 10 ms rise/fall, 2 Hz rate, 12 hr/night) from 25-55 days of age. Littermate controls were not exposed. Auditory brainstem thresholds and prepulse inhibition were then measured using 4, 8, 12, 16, and 24 kHz tones as stimuli and prepulses. Compared to nonexposed controls, the ABR thresholds of exposed mice were significantly better at the higher (16 and 24 kHz) frequencies after high-pass exposure. Females exposed to the high-pass AAE also had significantly better thresholds at 12 kHz. After low-pass exposure, ABR thresholds were significantly better for males at the lower (4 and 8 kHz) frequencies, but females showed no ABR effects of low-pass exposure. PPI was not affected by either exposure condition. Males in general (control and exposed) had poorer PPI at the higher frequencies. These results suggest that the AAE effects are somewhat localized to the acoustically stimulated areas, particularly in males, and not a result of more generalized nonauditory factors. Males and females, however, are affected differently by AAE exposure to lower frequencies.M.A. (Master of Arts