AUDITORY BEHAVIOURAL AND ELECTROPHYSIOLOGICAL RESPONSES IN ADULTS: EVALUATING CENTRAL AUDITORY PROCESSING

Abstract

Background: In addition to well known declines in the peripheral auditory system successful perception of speech is dependent on behavioural factors, as well as sound processing at subcortical and cortical levels. We hypothesized that cause and hence localization of impairment in the brain may be diverse in young and elderly people with hearing impairment, accordingly not always related with aging. The aim of the study is to determine the hallmarks of auditory behaviour and auditory cortical evoked responses that could be used in audiology clinics to help explain deficits in speech recognition in young and elderly listeners and recognize the most indicative effects of cortical auditory evoked potentials associated with difficulties of speech intelligibility. Material and methods: Three groups of adults participated: young normal hearing, young and elderly subjects with difficulty to understand speech especially in complex listening environments despite normal pure tone thresholds. We supposed that differences could be found between young and elderly subjects. Procedure involved behavioural hearing tests, dichotic word tests and sentence recognition test in quiet and noise, and electrophysiological measures as cortical auditory evoked potential components P1, N1, P2, P3 in quiet and noise. Results: Significant correlation was found between hearing behavioural tests and auditory cortical evoked potentials. This dichotic study demonstrated differences in cortical processing in people with good hearing, young and elderly listeners with speech recognition difficulties. Results provide information about central tests showing significant decrease of perception in young and elderly participants with hearing impairment and it is most strongly associated with event related potential response P3. Sensitivity to signal intensity level significantly changes in the group of young and elderly subjects with hearing impairment for responses P1, N1, P2(p<0.5). Conclusions: Despite of resembling results from behaviour tests outcomes of auditory evoked potentials mark less influence of signal intensity level latencies in young then in older subject group. They could be useful in audiology practice for clinical diagnostics and evaluation of hearing rehabilitation.