Linking age-related cochlear dysfunction to the perception of temporal fine structure

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Despite normal hearing thresholds, elderly people often have difficulties communicating in noisy situations. It has been suggested that this is due to a compromised perception of the temporal fine structure (TFS) of acoustic signals caused by its impaired representation in auditory nerve fibers. Such impairment may result from cochlear neuropathy affecting especially low spontaneous rate fibers or from deterioration of the endocochlear potential. By relating auditory discrimination of stimuli that relies on TFS in Mongolian gerbils of different ages to the representation of such stimuli by auditory-nerve fibers and the anatomical quantification of afferent synapses in the cochleae of the same individuals, we will provide correlational evidence for the proposed etiology of the perceptual deficits regarding TFS. By pharmacologically manipulating the cochlear neuropathy in young gerbils and evaluating TFS perception before and after the manipulation, we will further provide evidence for a causal link between the neuropathy and the ability to discriminate stimuli based on TFS. This combined approach will provide for an unprecedented level of understanding of the processes linking age-related cochlear dysfunction to the perception of TFS.