Possible Neurochemical and Neuroanatomical Bases of Age-Related Hearing Loss-Presbycusis

ABSTRACT

Broadly speaking, age-related hearing loss is a consequence of degenerative changes in the ear or brain. Sensitivity changes in the cochlea result from the loss of sensory (hair) cells, degeneration of auditory nerve fibers (eighth cranial nerve), or reductions in the endocochlear potential resulting from atrophy of the stria vascularis and its biochemical processes normally responsible for production of endolymph. These peripheral problems residing in the inner ear are the primary causes for declines in hearing sensitivity, as reflected in the presbycusic audiogram. The other main presenting symptom for elderly listeners is an inability to perceive speech or music in the presence of background noise. This significant handicap of our aged population, in fact the number one communication deficit of our senior generation, is due not only to losses of peripheral sensitivity to sound but also to age-related neural degeneration of the central auditory system. This article gives summary highlights of recent research on uncovering the neural bases of inner ear disorders and pathologies of the central auditory system that accompany normal aging. Implications for how audiologists and otolaryngologists may improve clinical diagnoses and offer novel future treatments are pointed out.

KEYWORD

Calcium-binding proteins - background noise - speech coding - temporal processing - auditory perception

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