The contribution of central auditory factors to auditory disability

Abstract

Gatehouse S. The contribution of central auditory factors to auditory disability. Acta Otolaryngol (Stockh) 1991; Suppl. 476: 182—188.

Auditory disability increases with both hearing threshold level and age. It is often suggested that some or most of the age effect in auditory disability is underpinned by deficits in central auditory function. A sample of 240 individuals aged between 50 and 75 years was examined to provide a balance across the major variables of hearing level and age. The central auditory indices investigated were: the binaural masking difference, the effects of dichotic competition on the staggered spondaic word test, the binaural advantage for diotically presented words, the binaural advantage for dichotically presented sentences, the effect of increasing the rate of presentation of speech, and the effect of nonsense as opposed to sensible sentences. In addition, the non—auditory variables of verbal and non—verbal IQ and the peripheral auditory factors of frequency and temporal resolution were assessed. Auditory disability was assessed using a performance index derived from a sentence identification—in—noise procedure and a procedure containing sense or nonsense sentences. Aspects of self—reported disability were determined using the MRC Institute of Hearing Research's Hearing Disability Questionnaire and the American Hearing Performance Inventory. There were significant correlations between the derived central variables and measured disability after control for hearing threshold levels and age. Central variables were correlated with self—reported disability for only the specific sub—score reflecting disability in localisation. On a multiple regression, the central variables explained 11.1% of the variance in performance index of disability above the 21.1% explained by hearing threshold levels and age. If age is not included in the equation, the central variables account for some but not all of the effect previously ascribed to age. The central auditory variables themselves were poorly related to the non—auditory variables of verbal and non—verbal IQ, suggesting they play a specifically auditory role as opposed to there being generally decreased processing ability.

Key Words:

• BMLD
• binaural competition
• binaural advantage
• speech identification