The term augmented acoustic environment (AAE) describes a period of controlled, nontraumatic acoustic stimulation. With an appropriate AAE, the auditory system of many hearing-impaired individuals can continue to be stimulated despite threshold elevations. The goal of the proposed research is to determine if AAEs can alter the time course and severity of progressive hearing loss and associated central changes such as neuronal degeneration in the anterior ventral cochlear nucleus (AVCN) and hearing-loss-induced plasticity in the inferior colliculus (IC), which we have - previously demonstrated in mice with age-related sensorineural hearing loss (C57BL/6J, DBA/2J, and BALB/CJ strains). They will be evaluated with auditory brainstem response thresholds, spiral ganglion cell counts, compound action potentials, distortion product otoacoustic emissions, histology of the AVCN, electrophysiological mapping of tonotopic organization in the AVCN and IC, and behaviorally by the amplitude of the acoustic startle response and by prepulse inhibition.
The aims are to obtain a better understanding of how the severity of sensorineural hearing loss is related to the ability of AAEs to modulate progressive cochlear and central changes, determine the relationship between the frequency spectrum of AAEs and changes in the auditory system associated with high-frequency hearing loss, determine if AAEs can modify the slowly progressing, late-onset hearing loss in aging CBA mice, and determine the outcomes of other parametric manipulations of AAES, such as the intensity, minimal duration, and temporal modulation of AAE stimuli. Because amplification (e.g., hearing-aids) is commonly given to presbycusis patients and others with sensorineural hearing loss, determining the effects of AAEs (good or bad) on the auditory system has great potential clinical importance.
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