Hearing aid acclimatization: The effect of amplification on auditory processing performance in adults

Abstract

Acclimatization is the slow improvement in auditory performance that occurs when the auditory system is exposed to novel acoustic cues. People using hearing aids for the first time are exposed to significant new acoustic input, and it has been suggested that acclimatization occurs in response, but there is mixed evidence to support this. Acclimatization has primarily been measured in terms of speech perception, although there is emerging evidence of plasticity in the lower levels of the auditory system such as the brainstem, that might underpin acclimatization in simpler auditory tasks. The present study investigated acclimatization in new hearing aid users, using a variety of auditory processing tasks. Performance was measured in four new hearing aid users before being fitted with hearing aids, and again eight weeks later, and the differences were compared to performance changes in ten experienced hearing aid users. No acclimatization effects were detected in tasks measuring speech perception in noise, dichotic listening, and temporal resolution. No changes were observed in acoustic reflex thresholds, which are non-behavioural brainstem responses that are sensitive to changes in acoustic input. The present study also investigated the relationship between auditory processing performance and the degree of hearing loss. The results suggested significant correlations between the degree of hearing loss, dichotic performance, and speech perception in noise test (HINT). In contrast, the random gap detection test (temporal resolution) was unaffected by hearing loss, indicating that it is appropriate for use in the hearing-impaired. Finally, evidence suggests that working memory may influence the degree of acclimatization, and can affect the performance of auditory processing tasks. A new auditory working memory task suitable for the hearing-impaired was devised and tested. Performance in the task, a listening span test, did not correlate with age or hearing loss, or with auditory processing task performance. Overall, no acclimatization effect was detected for auditory processing tasks in new users of hearing aids, and task performance was variably affected by hearing loss and age.