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.

A foundational measure of the auditory system's ability to process sound correctly is the auditory brainstem response (ABR) and middle latency response (MLR) complex, but their dependence on stimulus complexity and behavioral relevance is poorly understood. Here we recorded noninvasive, simultaneous electroencephalography (EEG) and magnetoencephalography (MEG) in adults listening to both naturalistic speech and clicks, and computed the resulting temporal response functions (TRFs). The TRF's ABR-MLR complex for speech listening contains a very early cortical peak (11 ms latency), which has not been well-characterized, and is absent for click stimuli. Other significant differences in latency and source between the speech and click MLR complexes point to further differences in their auditory processing, in thalamus and cortex. In contrast, the speech and click TRF's ABR complex both share a similar, prominent wave V response. In summation, the use of naturalistic speech reveals how early auditory responses reflect its ethological relevance.

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.

The relationship between pupil size, task performance, and self-reported effort has served as a fruitful way of understanding how listeners prepare (baseline or tonic pupil size) and deploy (task-evoked or phasic pupil response) cognitive resources during a listening task. However, changes in pupil size are sensitive not only to changes in listening effort but also physiological differences, some of which may be confounded across groups. Age is one such factor: older adults’ pupil size and dynamic range tend to diminish with age (senile miosis), obscuring researchers’ ability to compare how older and younger adults prepare and deploy listening effort. To account for this age-related physiological discrepancy in pupil size, methods to normalize or scale pupil size have been proposed. Whether these methods account for physiological differences while preserving potential task-evoked differences has not yet been evaluated. The present study seeks to address this by comparing three scaling methods (baseline subtraction, luminance dynamic range scaling, and task dynamic range scaling), as well as showing the pitfalls of performing no scaling at all. To accomplish this, pupil size was recorded while normal-hearing younger and older adults listened to 60-second storybook passages in quiet. The interaction between baseline pupil size and the task-evoked pupil response was analyzed using generalized additive mixed models. The results showed that applying no scaling at all or only performing baseline subtraction resulted in significantly smaller pupil responses in older compared to younger adults, while (luminance or task) dynamic range scaling was able to account for physiological differences between groups while simultaneously capturing the dynamic relationship between baseline pupil size and the task-evoked pupil response. Overall, the results of this study suggest that whether and how to apply within-participant scaling depends on the theoretical question to be addressed and the specifics of the study design and analyses.

Speech perception in noisy environments is a common challenge among older adults, even for those with clinically normal hearing. Cognitive decline may be one of the contributing factors, and, as such, auditory-cognitive training may enhance speech perception in these conditions. This study aims to determine if auditory-cognitive training can improve speech-in-noise listening in normal-hearing, older adults using neural and behavioral measures, supplemented with comparisons across younger and older adults. Neural responses were obtained using magnetoencephalography (MEG) while participants listened to long, narrative passages (60 s) under four noise conditions. Neural measures employed reverse correlation using encoding and decoding models, via the temporal response function (TRF) framework, to predict neural responses and reconstruct stimulus features, respectively, with the boosting algorithm to enforce sparsity. Behavioral measures, such as working memory (reading span; RSPAN), speech perception in noise (SPIN), and nonlinguistic auditory stream segregation (stochastic figure-ground; SFG) showed improvement post-training, along with neural and subjective ratings for listening effort. Additionally, auditory-cognitive training may enhance the neural contrast between the selectively attended and unattended stimulus reconstructions, and pre-training SFG performance may predict the extent of this neuroplasticity change. These results provide promising, additional insight into the effects of auditory-cognitive training, both perceptually and neurally.

Speech intelligibility among competing talkers becomes more difficult with age, even for older adults with clinically normal hearing. Recently, there has been a growing interest in the implementation of auditory-cognitive training to improve speech-in-noise recognition performance, particularly for older adults. In this study, we implemented two levels of cognitive demand in an adaptive auditory-cognitive training program that used a competing-speaker paradigm. Older adults with normal to near-normal hearing thresholds were assessed on training performance (at the individual and group level), self-reported training strategies, and far-transfer learning in a speech-perception-in-noise task. Training performance analysis revealed that some older adults, particularly those in the more demanding training, performed poorly during the auditory-cognitive training itself. Some participants in this group reported disengagement, potentially due to the low level of those individuals' self-reported satisfaction with engaging in challenging tasks in daily life. Despite these challenges, however, both groups generally improved in the far-transfer learning assessment, though there was variation among participants. Our results suggest that too-high levels of cognitive demand within the auditory-cognitive training may limit some aspects of training outcomes for speech perception in noise; however, higher cognitive demand may be beneficial for those who enjoy challenging tasks.

Increasing the sound intensity may lead to worse speech understanding, especially in noise. This is known as the “Rollover” phenomenon. There is mounting evidence that listening effort plays an important role in challenging listening conditions and can be directly quantified with objective measures such as pupil dilation. However, there is limited understanding of how listening effort relates to rollover in speech understanding. We hypothesized that listening effort plays an essential role in mitigating rollover effects to differential extents across age and hearing status. We recruited across the adult lifespan (N = 50, 20–83 years) with different hearing statuses in acoustic listeners and cochlear implant users to perform a speech discrimination task. Minimal word pairs were presented both in quiet and in 0 dB SNR babble noise, ranging from 35–85 dB SPL. Pupil area was tracked simultaneously with behavioral responses during the task. We found that normal-hearing listeners are fully able to utilize effort contributions to minimize rollover effects between in quiet and in noise conditions, with diminishing benefit as a function of age and increased hearing loss. The results of this project could broadly influence how to design future hearing devices and interventions that maximize hearing abilities for those affected by hearing loss.

Advancing age is associated with decreased sensitivity to temporal cues in word segments, particularly when target words follow non-informative carrier sentences or are spectrally degraded (e.g., vocoded to simulate cochlear-implant stimulation). This study investigated whether age, carrier sentences, and spectral degradation interacted to cause undue difficulty in processing speech temporal cues. Younger and older adults with normal hearing performed phonemic categorization tasks on two continua: a Buy/Pie contrast with voice onset time changes for the word-initial stop and a Dish/Ditch contrast with silent interval changes preceding the word-final fricative. Target words were presented in isolation or after non-informative carrier sentences, and were unprocessed or degraded via sinewave vocoding (2, 4, and 8 channels). Older listeners exhibited reduced sensitivity to both temporal cues compared to younger listeners. For the Buy/Pie contrast, age, carrier sentence, and spectral degradation interacted such that the largest age effects were seen for unprocessed words in the carrier sentence condition. This pattern differed from the Dish/Ditch contrast, where reducing spectral resolution exaggerated age effects, but introducing carrier sentences largely left the patterns unchanged. These results suggest that certain temporal cues are particularly susceptible to aging when placed in sentences, likely contributing to the difficulties of older cochlear-implant users in everyday environments.

Older listeners have difficulty processing temporal cues that are important for word discrimination, and deficient processing may limit their ability to benefit from these cues. Here, we investigated aging effects on perception and neural representation of the consonant transition and the factors that contribute to successful perception. To further understand the neural mechanisms underlying the changes in processing from brainstem to cortex, we also examined the factors that contribute to exaggerated amplitudes in cortex. We enrolled 30 younger normal-hearing and 30 older normal-hearing participants who met the criteria of clinically normal hearing. Perceptual identification functions were obtained for the words BEAT and WHEAT on a 7-step continuum of consonant-transition duration. Auditory brainstem responses (ABRs) were recorded to click stimuli and frequency-following responses (FFRs) and cortical auditory-evoked potentials were recorded to the endpoints of the BEAT-WHEAT continuum. Perceptual performance for identification of BEAT vs. WHEAT did not differ between younger and older listeners. However, both subcortical and cortical measures of neural representation showed age group differences, such that FFR phase locking was lower but cortical amplitudes (P1 and N1) were higher in older compared to younger listeners. ABR Wave I amplitude and FFR phase locking, but not audiometric thresholds, predicted early cortical amplitudes. Phase locking to the transition region and early cortical peak amplitudes (P1) predicted performance on the perceptual identification function. Overall, results suggest that the neural representation of transition durations and cortical overcompensation may contribute to the ability to perceive transition duration contrasts. Cortical overcompensation appears to be a maladaptive response to decreased neural firing/synchrony.

Objectives: This study was designed to examine the effects of hearing aid delay on the neural representation of the temporal envelope. It was hypothesized that the comb-filter effect would disrupt neural phase locking, and that shorter hearing aid delays would minimize this effect. Design: Twenty-one participants, ages 50 years and older, with bilateral mild-to-moderate sensorineural hearing loss were recruited through print advertisements in local senior newspapers. They were fitted with three different sets of hearing aids with average processing delays that ranged from 0.5 to 7 msec. Envelope-following responses (EFRs) were recorded to a 50-msec /da/ syllable presented through a speaker placed 1 meter in front of the participants while they wore the three sets of hearing aids with open tips. Phase-locking factor (PLF) and stimulus-to-response (STR) correlations were calculated from these recordings. Results: Recordings obtained while wearing hearing aids with a 0.5-msec processing delay showed higher PLF and STR correlations compared with those with either 5-msec or 7-msec delays. No differences were noted between recordings of hearing aids with 5-msec and 7-msec delays. The degree of difference between hearing aids was greater for individuals who had milder degrees of hearing loss. Conclusions: Hearing aid processing delays disrupt phase locking due to mixing of processed and unprocessed sounds in the ear canal when using open domes. Given previous work showing that better phase locking correlates with better speech-in-noise performance, consideration should be given to reducing hearing aid processing delay in the design of hearing aid algorithms.

The sounds we experience in our everyday communication can vary greatly in terms of level and background noise depending on the environment. Paradoxically, increasing the sound intensity may lead to worsened speech understanding, especially in noise. This is known as the "Rollover" phenomenon. There have been limited studies on rollover and how it is experienced differentially across aging groups, for those with and without hearing loss, as well as cochlear implant (CI) users. There is also mounting evidence that listening effort plays an important role in challenging listening conditions and can be directly quantified with objective measures such as pupil dilation. We found that listening effort was modulated by sound level and that rollover occurred primarily in the presence of background noise. The effect on listening effort was exacerbated by age and hearing loss in acoustic listeners, with greatest effect in older listeners with hearing loss, while there was no effect in CI users. The age- and hearing-dependent effects of rollover highlight the potential negative impact of amplification to high sound levels and therefore has implications for effective treatment of age-related hearing loss.

Understanding speech in a noisy environment is crucial in day-to-day interactions and yet becomes more challenging with age, even for healthy aging. Age-related changes in the neural mechanisms that enable speech-in-noise listening have been investigated previously; however, the extent to which age affects the timing and fidelity of encoding of target and interfering speech streams is not well understood. Using magnetoencephalography (MEG), we investigated how continuous speech is represented in auditory cortex in the presence of interfering speech in younger and older adults. Cortical representations were obtained from neural responses that time-locked to the speech envelopes with speech envelope reconstruction and temporal response functions (TRFs). TRFs showed three prominent peaks corresponding to auditory cortical processing stages: early (∼50 ms), middle (∼100 ms), and late (∼200 ms). Older adults showed exaggerated speech envelope representations compared with younger adults. Temporal analysis revealed both that the age-related exaggeration starts as early as ∼50 ms and that older adults needed a substantially longer integration time window to achieve their better reconstruction of the speech envelope. As expected, with increased speech masking envelope reconstruction for the attended talker decreased and all three TRF peaks were delayed, with aging contributing additionally to the reduction. Interestingly, for older adults the late peak was delayed, suggesting that this late peak may receive contributions from multiple sources. Together these results suggest that there are several mechanisms at play compensating for age-related temporal processing deficits at several stages but which are not able to fully reestablish unimpaired speech perception.NEW & NOTEWORTHY We observed age-related changes in cortical temporal processing of continuous speech that may be related to older adults' difficulty in understanding speech in noise. These changes occur in both timing and strength of the speech representations at different cortical processing stages and depend on both noise condition and selective attention. Critically, their dependence on noise condition changes dramatically among the early, middle, and late cortical processing stages, underscoring how aging differentially affects these stages.

Aging and hearing loss cause communication difficulties, particularly for speech perception in demanding situations, which have been associated with factors including cognitive processing and extended high-frequency (>8 kHz) hearing. Quantifying such associations and finding other (possibly unintuitive) associations is well suited to machine learning. We constructed ensemble models for 443 participants who varied in age and hearing loss. Audiometric, perceptual, electrophysiological, and cognitive data were used to predict speech perception in noise, reverberation, and with time compression. Speech perception was best predicted by variables associated with audiometric thresholds (including new across-frequency composite variables) between 1–4 kHz, followed by basic temporal processing ability. Cognitive factors and extended high-frequency thresholds had little to no predictive ability of speech perception. Future associations or lack thereof will inform the field as we attempt to better understand the intertwined effects of speech perception, aging, hearing loss, and cognition.

African American race and female sex are identified as protective for hearing sensitivity. The mechanisms supporting this protection are not fully understood and it is unclear whether similar mechanisms explain suprathreshold processing. Using robust linear and linear mixed-effect models, the best predictors of hearing sensitivity were contrasted with the best predictors of suprathreshold measures in younger and older listeners. The listeners (N=121) had thresholds <25 dB HL up to 3 kHz. Self-identified race (African American or Caucasian) and sex were hypothesized to moderate outcomes on hearing sensitivity, time-compressed speech recognition, pulse rate discrimination and auditory brainstem responses. Support for the hypotheses occurred if race and sex were among the predictors resulting in the models with lowest mean absolute error. The hypotheses were partially supported. However, confounding factors included 3 kHz hearing sensitivity (which moderated the association between sex, race, and Wave V latency) and episodic memory (which moderated the association between processing speed, sex, and pulse rate discrimination). Moreover, the hearing sensitivity benefit associated with African American listeners did not extend to suprathreshold measures. The biological mechanisms associated with race and sex, thought to underly differences in hearing sensitivity, may be inadequate to explain differences in auditory temporal processing.

Age-related hearing loss is one of the most prevalent health conditions in older adults. Although hearing aid technology has advanced dramatically, a large percentage of older adults do not use hearing aids. This untreated hearing loss may accelerate declines in cognitive and neural function and dramatically affect the quality of life. Our previous findings have shown that the use of hearing aids improves cortical and cognitive function and offsets subcortical physiological decline. The current study tested the time course of neural adaptation to hearing aids over the course of 6 months and aimed to determine whether early measures of cortical processing predict the capacity for neural plasticity. Seventeen (9 females) older adults (mean age = 75 years) with age-related hearing loss with no history of hearing aid use were fit with bilateral hearing aids and tested in six testing sessions. Neural changes were observed as early as 2 weeks following the initial fitting of hearing aids. Increases in N1 amplitudes were observed as early as 2 weeks following the hearing aid fitting, whereas changes in P2 amplitudes were not observed until 12 weeks of hearing aid use. The findings suggest that increased audibility through hearing aids may facilitate rapid increases in cortical detection, but a longer time period of exposure to amplified sound may be required to integrate features of the signal and form auditory object representations. The results also showed a relationship between neural responses in earlier sessions and the change predicted after 6 months of the use of hearing aids. This study demonstrates rapid cortical adaptation to increased auditory input. Knowledge of the time course of neural adaptation may aid audiologists in counseling their patients, especially those who are struggling to adjust to amplification. A future comparison of a control group with no use of hearing aids that undergoes the same testing sessions as the study's group will validate these findings.

For listeners with acoustic hearing, aging and hearing loss are associated with temporal processing deficits. For those with enough hearing loss, a cochlear implant (CI) becomes the preferred intervention. However, a CI degrades acoustic information by delivering primarily temporal envelope information through modulated electrical pulse trains. Therefore, if older CI listeners experience temporal processing deficits like acoustic-hearing listeners, they are compelled to understand speech primarily through a process that is affected by aging. We will present temporal processing data from a series of experiments that use word contrasts that vary primarily in a temporal dimension (silence duration: Dish-Ditch; voice-onset time: Buy-Pie). Participants include CI listeners and normal-hearing listeners presented with a CI simulation via a channel vocoder and range in age from younger (<45 yrs) to older (>65 yrs). Results show that CI listeners and NH listeners presented with CI simulations need longer temporal cues to discriminate temporally based word contrasts. In addition, such deficits are differentially worse at higher stimulation levels for the older CI listeners compared to the younger CI and all NH listeners. In conclusion, aging may lead to temporal processing deficits in CI listeners. These results have implications for CI programming and directions for technological improvements.

The ability to understand speech in complex environments depends on the brain’s ability to preserve the precise timing characteristics of the speech signal. Age-related declines in temporal processing may contribute to the older adult’s experience of communication difficulty in challenging listening conditions. This study’s purpose was to evaluate the effects of rate discrimination training on auditory temporal processing. A double-blind, randomized control design assigned 77 young normal-hearing, older normal-hearing, and older hearing-impaired listeners to one of two treatment groups: experimental (rate discrimination for 100- and 300-Hz pulse trains) and active control (tone detection in noise). All listeners were evaluated during pre- and post-training sessions using perceptual rate discrimination of 100-, 200-, 300-, and 400-Hz band-limited pulse trains and auditory steady-state responses (ASSRs) to the same stimuli. Training generalization was evaluated using several temporal processing measures and sentence recognition tests that included time-compressed and reverberant speech stimuli. Results demonstrated a session × training group interaction for perceptual and ASSR testing to the trained frequencies (100 and 300 Hz), driven by greater improvements in the training group than in the active control group. Further, post-test rate discrimination of the older listeners reached levels that were equivalent to those of the younger listeners at pre-test. Generalization was observed in significant improvement in rate discrimination of untrained frequencies (200 and 400 Hz) and in correlations between performance changes in rate discrimination and sentence recognition of reverberant speech. Further, non-auditory inhibition/attention performance predicted training-related improvement in rate discrimination. Overall, the results demonstrate the potential for auditory training to partially restore temporal processing in older listeners and highlight the role of cognitive function in these gains.

Auditory temporal processing declines with age, leading to potential deleterious effects on communication. In young normal-hearing listeners, perceptual rate discrimination is rate limited around 300 Hz. It is not known whether this rate limitation is similar in older listeners with hearing loss. The purpose of this study was to investigate age- and hearing-loss-related rate limitations on perceptual rate discrimination, and age- and hearing-loss-related effects on neural representation of these stimuli. Younger normal-hearing, older normal-hearing, and older hearing-impaired listeners performed a pulse-rate discrimination task at rates of 100, 200, 300, and 400 Hz. Neural phase locking was assessed using the auditory steady-state response. Finally, a battery of non-auditory cognitive tests was administered. Younger listeners had better rate discrimination, higher phase locking, and higher cognitive scores compared to both groups of older listeners. Aging, but not hearing loss, diminished neural-rate encoding and perceptual performance; however, there was no relationship between the perceptual and neural measures. Higher cognitive scores were correlated with improved perceptual performance, but not with neural phase locking. This study shows that aging, rather than hearing loss, may be a stronger contributor to poorer temporal processing, and cognitive factors such as processing speed and inhibitory control may be related to these declines.

Objectives: The role of subcortical synchrony in speech-in-noise (SIN) recognition and the frequency-following response (FFR) was examined in multiple listeners with auditory neuropathy. Although an absent FFR has been documented in one listener with idiopathic neuropathy who has severe difficulty recognizing SIN, several etiologies cause the neuropathy phenotype. Consequently, it is necessary to replicate absent FFRs and concomitant SIN difficulties in patients with multiple sources and clinical presentations of neuropathy to elucidate fully the importance of subcortical neural synchrony for the FFR and SIN recognition. Design: Case series. Three children with auditory neuropathy (two males with neuropathy attributed to hyperbilirubinemia, one female with a rare missense mutation in the OPA1 gene) were compared to age-matched controls with normal hearing (52 for electrophysiology and 48 for speech recognition testing). Tests included standard audiological evaluations, FFRs, and sentence recognition in noise. The three children with neuropathy had a range of clinical presentations, including moderate sensorineural hearing loss, use of a cochlear implant, and a rapid progressive hearing loss. Results: Children with neuropathy generally had good speech recognition in quiet but substantial difficulties in noise. These SIN difficulties were somewhat mitigated by a clear speaking style and presenting words in a high semantic context. In the children with neuropathy, FFRs were absent from all tested stimuli. In contrast, age-matched controls had reliable FFRs. Conclusion: Subcortical synchrony is subject to multiple forms of disruption but results in a consistent phenotype of an absent FFR and substantial difficulties recognizing SIN. These results support the hypothesis that subcortical synchrony is necessary for the FFR. Thus, in healthy listeners, the FFR may reflect subcortical neural processes important for SIN recognition.

When listening to degraded speech, listeners can use high-level semantic information to support recognition. The literature contains conflicting findings regarding older listeners' ability to benefit from semantic cues in recognizing speech, relative to younger listeners. Electrophysiologic (EEG) measures of lexical access (N400) often show that semantic context does not facilitate lexical access in older listeners; in contrast, auditory behavioral studies indicate that semantic context improves speech recognition in older listeners as much as or more than in younger listeners. Many behavioral studies of aging and the context benefit have employed signal degradation or alteration, whereas this stimulus manipulation has been absent in the EEG literature, a possible reason for the inconsistencies between studies. Here we compared the context benefit as a function of age and signal type, using EEG combined with behavioral measures. Non-native accent, a common form of signal alteration which many older adults report as a challenge in daily speech recognition, was utilized for testing. The stimuli included English sentences produced by native speakers of English and Spanish, containing target words differing in cloze probability. Listeners performed a word identification task while 32-channel cortical responses were recorded. Results show that older adults' word identification performance was poorer in the low-predictability and non-native talker conditions than the younger adults', replicating earlier behavioral findings. However, older adults did not show reduction or delay in the average N400 response as compared to younger listeners, suggesting no age-related reduction in predictive processing capability. Potential sources for discrepancies in the prior literature are discussed.