The age effect on auditory processing

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Studying young versus middle-aged subjects may be a more effective way of avoiding the confound of high-frequency hearing loss in elderly persons when studying age effects on auditory processing, according to researchers at the University of Alabama.

Researchers in the past have been challenged by various dimensions of auditory processing -- especially the perception of speech in the presence of background competition -- which have been shown to deteriorate with age, say the authors. “A persistent problem in the assessment of these age-related changes has been the high prevalence of age-related high-frequency hearing loss in elderly persons.” It has been suggested that a more productive approach to the study of age-related decline might be to study middle-aged, rather than elderly, persons, where confounding high-frequency hearing loss is less prevalent. The researchers set out to determine whether an increase in the left-ear disadvantage (LED) in dichotic listening could be demonstrated in a group of middle-aged persons.

Researchers utilized the N400 component of the auditory event-related potential (AERP) to evaluate interaural asymmetry in a quasi-dichotic competing speech task. Electrophysiological responses were obtained on a word-pair semantic categorization task presented through a front loudspeaker while the listener ignored competing speech presented through either left (competition left [CL]) or right (competition right [CR]) loudspeakers. Subjects included twenty young (18-24 yr) and 20 middle-aged (44-57 yr) females with normal hearing sensitivity. Individual, as well as grand-averaged, AERP waveforms and scalp topographies were analyzed for the word pairs. Peak amplitude and latency measures of the N400 component were subjected to a mixed design analysis of variance (ANOVA).

The results showed no significant interaural asymmetry in the AERP waveform for the reference word condition in either age group. In response to the second word of the pair, however, middle-aged females showed significantly greater N400 negativity in the CR condition than in the CL condition. There was no significant laterality effect found in the young females.

Source:Journal of the American Academy of Audiology

Rose Simpson