Page 18 - Winter2018

Age-Related Hearing Loss
mounted on a pair of eyeglasses to track the direction of the listener’s gaze (Kidd et al., 2013), which may indicate the listener’s focus of attention. The information regarding the direction of gaze is then used to maximize the directionality of a multimicrophone array.
The idea of “brain-controlled” hearing aids is certainly ap- pealing. Nevertheless, the ability to benefit from this strat- egy is still limited by the ability of the auditory system to accurately process the amplified signal. As mentioned in The Audiological Evaluation, aging and hearing loss can disrupt the processing of the timing and frequency aspects of speech. The potential for neuroplastic changes in the ag- ing auditory system has not yet been fully explored. There is some evidence that the use of hearing aids over time may improve the neural processing of speech signals, and that changes in cortical processing relate to improvements in cognitive function (Karawani et al., 2018), but more re- search is needed to explore the limits of neuroplasticity.
Outcomes may be improved if hearing aid use is supplement- ed with auditory training. But evidence for the potential ben- efits of auditory training to provide long-term improvement of perception and neural function has been mixed. A large- scale randomized control trial was conducted to evaluate the effects of supplementing hearing aid use with 10 hours of au- ditory training with Listening and Communication Enhance- ment Training (LACE) in 279 veterans and found that LACE training did not result in better outcomes than those obtained with standard-of-care hearing aid intervention alone (Saun- ders et al., 2016). Another study assessed the effects of 40 hours of auditory-based cognitive training in 29 older adults with and without hearing loss and found that the training im- proved performance on the QuickSIN and also reduced exag- geration of the speech envelope in older adults with hearing loss (Anderson et al., 2013b). Although the Anderson et al. study suggests that a sufficient number of hours of training may engender neuroplastic changes, the improvement in perception was relatively small and would not be considered clinically significant. It is possible that a behavioral measure of perception obtained in a laboratory setting does not cap- ture training-related improvements that are experienced in real-life settings. Older adults with hearing loss expend more effort to understand speech, especially in noisy settings. An individual who expends considerable effort to understand what is said will not be able to maintain that level of effort over the long term. When effort cannot be sustained, speech perception may decrease and the individual begins to with- draw from the conversation. An objective measure of cogni-
16 | Acoustics Today | Winter 2018
tive effort, such as pupillometry (a measure of pupil size and reactivity), may be a more sensitive assessment of training benefits than measures of speech recognition alone. Kuchin- sky et al. (2016) found that twenty 90-minute sessions that trained word recognition in noise resulted in pupillometry changes that reflected a decrease in cognitive effort and im- proved word recognition in 29 older adults with hearing loss. Many questions remain unanswered regarding the potential for training to improve speech understanding in older adults. Studies are underway to assess the benefits of training that target age-related temporal processing deficits and auditory- cognitive interactions in older adults. A better understand- ing of training strategies that engender neuroplastic changes in older adults should lead to better outcomes and improved communication and social function in older adults.
Summary
Age-related hearing loss has many potential consequences for the quality of life, including social withdrawal and pos- sible loss of cognitive function. It is therefore important to provide timely audiological assessment and management to individuals who appear to be having difficulty hearing and understanding speech. Nevertheless, aging brings additional challenges to identifying the source of speech-understand- ing problems, including disruptions in the transmission or processing of speech stimuli that can occur at all levels of the auditory system and the brain. Age-related cognitive decline may also contribute to speech-understanding problems. Therefore, it is imperative to identify and manage hearing loss to minimize the impact of cognitive decline. These dis- ruptions may limit the benefit that can be obtained from hearing aid amplification and auditory training. Research is ongoing to optimize hearing aid technology using neural feedback regarding the listener’s focus of attention. The de- velopment of effective auditory training programs may also improve hearing aid outcomes. Improved assessment and management protocols should improve the ability of older adults (including your grandmother) to maintain a healthy, active social life despite hearing loss.
References
Anderson, S., Parbery-Clark, A., White-Schwoch, T., and Kraus, N. (2013a). Auditory brainstem response to complex sounds predicts self-reported speech-in-noise performance. Journal of Speech, Language, and Hearing Research 56(1), 31-43.
Anderson, S., White-Schwoch, T., Choi, H. J., and Kraus, N. (2013b). Train- ing changes processing of speech cues in older adults with hearing loss. Frontiers in Systems Neuroscience 7(97), 1-9. https://doi.org/10.3389/fn- sys.2013.00097.