Samira Anderson

Aging and hearing loss are associated with difficulty understanding fast speech. Here, we investigated how peripheral hearing sensitivity, neural speech representation, and cognitive processing contribute to this difficulty. For this purpose, we collected electrophysiological, cognitive, and behavioral assessments from 30 younger normal-hearing adults, 32 older normal-hearing adults, and 26 older hearing-impaired adults. Subcortical envelope-following responses to monosyllabic words and cortical envelope tracking to continuous speech were recorded at 0% and 40% time compression. Cognitive performance was assessed using the NIH Toolbox. Time-compressed sentence recognition was measured using an adaptive approach to determine the time compression ratio that corresponded to 50% correct performance. Younger participants showed stronger subcortical envelope encoding than older participants, and phase locking decreased with time compression across groups. Cortical envelope tracking was greater in older adults, with and without hearing loss, than in younger participants, and increased in the time-compression condition. Younger participants had higher processing speed scores than older participants and achieved 50% correct performance with higher time compression ratios than older participants. Audiometric thresholds, cortical envelope tracking to natural-rate speech, and processing speed significantly predicted time-compressed speech recognition performance. These results suggest that while both peripheral hearing sensitivity and processing speed are predictive of time-compressed speech recognition, cortical mechanisms appear to contribute to time-compressed speech recognition primarily when temporal cues are faithfully preserved in the speech signal.

As humans age, circadian/diurnal preferences typically shift to earlier times of day. Recent research identifies the fatigue associated with listening effort as a fundamental concern among listeners with hearing impairment. The impact of time-of-day on perceiving speech under challenging listening conditions is, however, not well established for older listeners with hearing loss. A study was therefore initiated to measure time-of-day effects. Experienced cochlear-implant users with postlingual onsets of hearing loss completed several effortful perceptual tasks either in the morning, mid-afternoon, or at both timepoints. Sentence pairs were presented in quiet listening conditions and listeners were cued either before or after presentation, to repeat the first, second, or both sentences. Speech-in-noise (+10 SNR) scores for single sentences were also recorded. Following this, information was collected regarding time-of-day preferences, sleep habits, and fatigue, along with standardized measures of visual attention, processing speed, and working memory. Preliminary data do not currently bear out participants' intuitions regarding performance in the morning versus afternoon. Although memory load and target uncertainty reduce scores, performance across timepoints appears similar, irrespective of time-of-day-preference. Additional data for speech-in-noise will be reported.