Neural substrates for presbycusis: Anatomy, chemistry, and neuroimaging of the central auditory system

Abstract

Overall, loss of hearing with age involves at least two main components: Reductions in sensitivity to sounds, starting with the high frequencies, and a decline in the ability to understand speech in the presence of background noise. The former is intimately linked to the age-related loss of: sensory cells, stria vascularis metabolic activity, and auditory-nerve fibers. The latter is affected by these peripheral changes, as well as by the pathologies of the central auditory system that occur with age. Recent findings concerning age-related plasticity in the structure, chemistry, and functional anatomy of the central auditory system will be presented to shed light on changes in the brain that may underlie the physiological and perceptual deficits in the processing of biologically relevant sounds presented by the other speakers of this session. Some changes include: declines in central auditory pathway connectivity, changes in the presence of calcium-binding proteins critical for intracellular calcium regulation and optimal neural functioning, reductions in GABA neurochemistry at the midbrain level, and changes in activity of the human brain during the processing of speech in background noise as seen in PET imaging experiments. [Work suported by NIA–NIH, and the International Center for Hearing & Speech Research, Rochester, NY.]