The Effect of Sleep on Perceptual Learning and Memory Consolidation

An ability to segregate speech accurately is essential given that most auditory environments contain other overlapping conversations or environmental noise. While perceiving speech among background noise can be difficult in and of itself, those with hearing impairments can experience considerable difficulty. While training has been shown to benefit perceptual segregation of trained sounds, it is unclear how such training transfers to sounds not included in a training regimen. The current study aimed to address this question by training listeners on a portion of sounds during a vowel segregation task, and subsequently testing on both the trained sounds and untrained sounds. Additionally, the dependency on sleep in consolidating generalization was investigated by testing listeners at two additional time points: before sleep (12 hours later) and after sleep (24 hours later). Finally, neural correlates specific to generalization was investigated by recording brain activity (EEG) during all test and training sessions. Trained listeners significantly improved on trained and untrained vowel pairs, demonstrating training-induced learning and generalization. The control group also significantly improved across test sessions, demonstrating testing-induced learning. Spatio-temporal analyses of EEG data revealed that generalization learning was paralleled by a source configuration change, while rote learning was paralleled by a change in the power of the neural response. These results confirm that learning gained through speech segregation is generalizable to new sounds, as well as revealed a neural pattern of activity that may index the processes responsible for transferring learning to untrained sounds. Finally, time and additional practice appear to greater contribute to learning overall, as compared to sleep

Age-related deficits in dip-listening evident for isolated sentences but not for spoken stories

Fluctuating background sounds facilitate speech intelligibility by providing speech ‘glimpses’ (masking release). Older adults benefit less from glimpses, but masking release is typically investigated using isolated sentences. Recent work indicates that using engaging, continuous speech materials (e.g., spoken stories) may qualitatively alter speech-in-noise listening. Moreover, neural sensitivity to different amplitude envelope profiles (ramped, damped) changes with age, but whether this affects speech listening is unknown. In three online experiments, we investigate how masking release in younger and older adults differs for masked sentences and stories, and how speech intelligibility varies with masker amplitude profile. Intelligibility was generally greater for damped than ramped maskers. Masking release was reduced in older relative to younger adults for disconnected sentences, and stories with a randomized sentence order. Critically, when listening to stories with an engaging and coherent narrative, older adults demonstrated equal or greater masking release compared to younger adults. Older adults thus appear to benefit from ‘glimpses’ as much as, or more than, younger adults when the speech they are listening to follows a coherent topical thread. Our results highlight the importance of cognitive and motivational factors for speech understanding, and suggest that previous work may have underestimated speech-listening abilities in older adults

The effect of musical training on speech and sound perception

We are going to carry out such a study, in conjunction with research labs at five other institutions. With six universities involved, we will be able to recruit a sufficiently large number of people in the study and decrease the likelihood of any regional bias influencing the outcomes. We will be trying to validate the following claims: that musicians have an improved ability to understand speech in noisy environments that the responses of a musician\u27s brainstem to speech sounds is enhanced, and that older musicians have reduced symptoms from age-related hearing loss.https://ir.lib.uwo.ca/brainscanprojectsummaries/1036/thumbnail.jp

Cortical responses to the amplitude envelopes of sounds change with age

Many older listeners have difficulty understanding speech in noise, when cues to speech-sound identity are less redundant. The amplitude envelope of speech fluctuates dramatically over time, and features such as the rate of amplitude change at onsets (attack) and offsets (decay), signal critical information about the identity of speech sounds. Aging is also thought to be accompanied by increases in cortical excitability, which may differentially alter sensitivity to envelope dynamics. Here, we recorded electroencephalography in younger and older human adults (of both sexes) to investigate how aging affects neural synchronization to 4 Hz amplitude-modulated noises with different envelope shapes (ramped: Slow attack and sharp decay; damped: Sharp attack and slow decay). We observed that subcortical responses did not differ between age groups, whereas older compared with younger adults exhibited larger cortical responses to sound onsets, consistent with an increase in auditory cortical excitability. Neural activity in older adults synchronized more strongly to rapid-onset, slow-offset (damped) envelopes, was less sinusoidal, and was more peaked. Younger adults demonstrated the opposite pattern, showing stronger synchronization to slow-onset, rapid-offset (ramped) envelopes, as well as a more sinusoidal neural response shape. The current results suggest that age-related changes in the excitability of auditory cortex alter responses to envelope dynamics. This may be part of the reason why older adults experience difficulty understanding speech in noise

Change Deafness: A Comprehensive Examinations

Environmental changes are a vital source of information which can drive advantageous behavioral responses. For example, detecting visual changes can be critical when driving a vehicle or when simply walking down a busy street. Auditory perception is an essential complement to vision as it can allow awareness of changes in and out of sight. While subjective perception would suggest that our sensory representation of the world is complete, research on change deafness indicates that quite often the opposite is true. Healthy listeners often miss salient, suprathreshold auditory changes. Three separate manuscripts will be presented, each of which aims to advance the current understanding of change deafness using a different approach. The first manuscript examined how focused attention modulates auditory scene perception, and found that attention to change-relevant objects is crucial for successful change detection, and that encouraging broad attention to multiple objects is the best way to reduce change deafness. The second manuscript examined whether auditory memory limitations are a significant cause of change deafness, and found that change detection is generally limited by capacity, but that auditory memory long lasting for sounds with naturalistic acoustic structures. Finally, the third manuscript determines whether change deafness can be reduced by training, and found that auditory change detection can be enhanced relatively rapidly, although the training regimen type can determine whether improvement occurs immediately (fast learning) or if learning continues to develop hour after training ceased (slow learning). Together, the data generated from these experiments has led to a better understanding of what causes change detection error and whether it can be reduced

Neural Activity during Story Listening Is Synchronized across Individuals Despite Acoustic Masking.

Older people with hearing problems often experience difficulties understanding speech in the presence of background sound. As a result, they may disengage in social situations, which has been associated with negative psychosocial health outcomes. Measuring listening (dis)engagement during challenging listening situations has received little attention thus far. We recruit young, normal-hearing human adults (both sexes) and investigate how speech intelligibility and engagement during naturalistic story listening is affected by the level of acoustic masking (12-talker babble) at different signal-to-noise ratios (SNRs). In Experiment 1, we observed that word-report scores were above 80% for all but the lowest SNR (-3 dB SNR) we tested, at which performance dropped to 54%. In Experiment 2, we calculated intersubject correlation (ISC) using EEG data to identify dynamic spatial patterns of shared neural activity evoked by the stories. ISC has been used as a neural measure of participants\u27 engagement with naturalistic materials. Our results show that ISC was stable across all but the lowest SNRs, despite reduced speech intelligibility. Comparing ISC and intelligibility demonstrated that word-report performance declined more strongly with decreasing SNR compared to ISC. Our measure of neural engagement suggests that individuals remain engaged in story listening despite missing words because of background noise. Our work provides a potentially fruitful approach to investigate listener engagement with naturalistic, spoken stories that may be used to investigate (dis)engagement in older adults with hearing impairment

Age-related deficits in dip-listening evident for isolated sentences but not for spoken stories

Fluctuating background sounds facilitate speech intelligibility by providing speech ‘glimpses’ (masking release). Older adults benefit less from glimpses, but masking release is typically investigated using isolated sentences. Recent work indicates that using engaging, continuous speech materials (e.g., spoken stories) may qualitatively alter speech-in-noise listening. Moreover, neural sensitivity to different amplitude envelope profiles (ramped, damped) changes with age, but whether this affects speech listening is unknown. In three online experiments, we investigate how masking release in younger and older adults differs for masked sentences and stories, and how speech intelligibility varies with masker amplitude profile. Intelligibility was generally greater for damped than ramped maskers. Masking release was reduced in older relative to younger adults for disconnected sentences, and stories with a randomized sentence order. Critically, when listening to stories with an engaging and coherent narrative, older adults demonstrated equal or greater masking release compared to younger adults. Older adults thus appear to benefit from ‘glimpses’ as much as, or more than, younger adults when the speech they are listening to follows a coherent topical thread. Our results highlight the importance of cognitive and motivational factors for speech understanding, and suggest that previous work may have underestimated speech-listening abilities in older adults

Change deafness and object encoding with recognizable and unrecognizable sounds

Change deafness is the failure to notice changes in an auditory scene. In this study, we sought to determine if change deafness is a perceptual error, rather than only a reflection of verbal memory limitations. We also examined how successful encoding of objects within a scene is related to successful detection of changes. Event-related potentials (ERPs) were recorded while listeners completed a change-detection and an object-encoding task with scenes composed of recognizable sounds or unrecognizable temporally scrambled versions of the recognizable sounds. More change deafness occurred for the unrecognizable, compared to recognizable sounds, indicating that change deafness is a perceptual error and not solely a product of verbal memory. ERPs from both the recognizable and unrecognizable scenes revealed an enhanced P3b (at PZ/1/2, POZ/3/4 from 350 to 750 ms) to detected changes, a marker that conscious change detection has occurred. Recognizable scenes resulted in an enhanced T400 (at T8/TP8, C6/CP6 from 315 to 660 ms) to detected changes, possibly indicating activation of established memory representations. Unrecognizable scenes elicited an enhanced P3a (at FCZ/1/2 from 280 to 600 ms) to detected changes, indicating enhanced orienting to acoustic change. Performance on the object-encoding task revealed that change deafness was reduced, but not eliminated, when performance on the object-encoding task was accurate