Aging effects on binaural listening and other auditory system assessments

Older listeners are known to have decreased sound localization and hearing in noise abilities compared to young listeners, even when exhibiting clinically normal hearing. We hypothesize that these deficits may be related to decreased temporal precision of neural activity in the sound localization processing pathway, and/or other central auditory system deficits involving more complex functions such as speech recognition. Presented here are preliminary results from a study underway on the impact of aging on auditory functioning, and in particular, binaural processing. Subjects range from 21 to 89 years of age, have normal or near normal-hearing sensitivity, and are being evaluated on assessments of auditory system integrity and behavioral performance. Primary outcome measures include speech understanding in noise, auditory brainstem responses (ABRs) and the calculated ABR binaural interaction component, behavioral measures of spatial acuity, and a subjective questionnaire of hearing handicap. Secondary measures include temporal fine structure and spectro-temporal modulation sensitivity tests, otoacoustic emissions, and electrocochleography. In addition, extended-high-frequency hearing thresholds are measured and working memory assessed. Early results show an aging effect across decades of life on several of these measures. Greatest aging effects are seen in the more adverse listening conditions from behavioral testing. [Support: R01-DC017924.]