Perceptual sensitivity to, and electrophysiological encoding of, a complex periodic signal: effects of age

On prediction of aided behavioural measures using speech auditory brainstem responses and decision trees

Current clinical strategies to assess benefits from hearing aids (HAs) are based on self-reported questionnaires and speech-in-noise (SIN) tests; which require behavioural cooperation. Instead, objective measures based on Auditory Brainstem Responses (ABRs) to speech stimuli would not require the individuals' cooperation. Here, we re-analysed an existing dataset to predict behavioural measures with speech-ABRs using regression trees. Ninety-two HA users completed a self-reported questionnaire (SSQ-Speech) and performed two aided SIN tests: sentences in noise (BKB-SIN) and vowel-consonant-vowels (VCV) in noise. Speech-ABRs were evoked by a 40 ms [da] and recorded in 2x2 conditions: aided vs. unaided and quiet vs. background noise. For each recording condition, two sets of features were extracted: 1) amplitudes and latencies of speech-ABR peaks, 2) amplitudes and latencies of speech-ABR F0 encoding. Two regression trees were fitted for each of the three behavioural measures with either feature set and age, digit-span forward and backward, and pure tone average (PTA) as possible predictors. The PTA was the only predictor in the SSQ-Speech trees. In the BKB-SIN trees, performance was predicted by the aided latency of peak F in quiet for participants with PTAs between 43 and 61 dB HL. In the VCV trees, performance was predicted by the aided F0 encoding latency and the aided amplitude of peak VA in quiet for participants with PTAs ≤ 47 dB HL. These findings indicate that PTA was more informative than any speech-ABR measure, as these were relevant only for a subset of the participants. Therefore, speech-ABRs evoked by a 40 ms [da] are not a clinical predictor of behavioural measures in HA users.

Speech Understanding in Modulated Noise and Speech Maskers as a Function of Cognitive Status in Older Adults

Objectives The purpose of this study was to investigate the impact of different types of maskers on speech understanding as a function of cognitive status in older adults. The hypothesis tested was that individuals with a diagnosis of mild cognitive impairment (MCI) or mild dementia would perform like their age- and hearing status-matched control counterparts in modulated noise but would perform more poorly in the presence of competing speech. Design Participants (n = 39; age range: 55-77 years old) performed a speech-in-noise task and completed two cognitive screening tests and a measure of working memory. Sentences were presented in the presence of two types of maskers (i.e., speech envelope-modulated noise and two-talker, same-sex competing speech). Two analyses were undertaken: (a) a between-groups comparison of individuals diagnosed with MCI/dementia, individuals who failed both cognitive screeners (possible MCI), and age- and hearing status-matched neurologically healthy control individuals and (b) a mixed-model analysis of variance of speech perception performance as a function of working memory capacity. Results The between-groups comparison yielded significant group differences for speech understanding in both masking conditions, with the MCI/dementia group performing more poorly than the neurologically healthy controls and possible MCI groups. A single measure of working memory (Size Comparison Span [SICSPAN]) was correlated with performance on the speech perception task in the competing speech conditions. Conclusions Adults with a diagnosis of MCI or mild dementia performed more poorly on a speech perception task than their age- and hearing status-matched control counterparts in the presence of both maskers, with larger group mean differences when the target speech was presented in a two-talker masker. This suggests increased difficulty understanding speech in the presence of distracting backgrounds for people with MCI/dementia. Future studies should consider how to target this potentially vulnerable population as they may be experiencing increased difficulty communicating in challenging environments.