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Purpose: The purpose of this article is to review recent research from our laboratory on the topic of aging, and the ear-brain system, as it relates to hearing aid use and auditory rehabilitation. The material described here was presented as part of the forum on the brain and hearing aids, at the 2014 HEaling Across the Lifespan (HEAL) conference. Method: The method involves a narrative review of previously reported electroencephalography (EEG) and magnetoencephalography (MEG) data from our laboratory as they relate to the (a) neural detection of amplified sound and (b) ability to learn new sound contrasts. Conclusions: Results from our studies add to the mounting evidence that there are central effects of biological aging as well as peripheral pathology that affect a person's neural detection and use of sound. What is more, these biological effects can be seen as early as middle age. The accruing evidence has implications for hearing aid use because effective communication relies not only on sufficient detection of sound but also on the individual's ability to learn to make use of these sounds in ever-changing listening environments. [ABSTRACT FROM AUTHOR]

Performance variability among people who wear hearing aids presents a challenge for clinicians. Although some clients appear to make use of amplified signals with little effort, other clients report frustration and may reject their hearing aids altogether. Some of the explanations underlying performance variability likely result from a poorly fitted device; others might result from reasons related to how the amplified signal is being represented in the central auditory system.We believe that perception is dependent on the neural detection, representation, and integration of the amplified speech and noise. For this reason it is important to understand how amplification modifies the acoustic content of a signal as well as the neural representation of the amplified sound. It is therefore necessary to examine the interaction between hearing aid-processed acoustic input and the neural networks that are activated. Here we focus on the role of brainstem encoding to determine if auditory brainstem responses might provide information to help explain why some people are able to make better use of amplified sound than others. More specifically, we review the literature to determine if brainstem measures might someday be used to guide clinicians when fitting a hearing aid. [ABSTRACT FROM AUTHOR]

Performance variability among people who wear hearing aids presents a challenge for clinicians. Although some clients appear to make use of amplified signals with little effort, other clients report frustration and may reject their hearing aids altogether. Some of the explanations underlying performance variability likely result from a poorly fitted device; others might result from reasons related to how the amplified signal is being represented in the central auditory system.We believe that perception is dependent on the neural detection, representation, and integration of the amplified speech and noise. For this reason it is important to understand how amplification modifies the acoustic content of a signal as well as the neural representation of the amplified sound. It is therefore necessary to examine the interaction between hearing aid-processed acoustic input and the neural networks that are activated. Here we focus on the role of brainstem encoding to determine if auditory brainstem responses might provide information to help explain why some people are able to make better use of amplified sound than others. More specifically, we review the literature to determine if brainstem measures might someday be used to guide clinicians when fitting a hearing aid. [ABSTRACT FROM AUTHOR]

Background: Older adults, with or without normal peripheral hearing sensitivity, have difficulty understanding speech. This impaired speech perception may, in part, be due to desynchronization affecting the neural representation of acoustic features. Here we determine if phase-locked neural activity generating the brainstem frequency-following response (FFR) exhibits age-related desynchronization and how this degradation affects the neural representation of simple and complex sounds. Purpose: The objectives of this study were to (1) characterize the effects of age on the neural representation of simple tones and complex consonant-vowel stimuli, (2) determine if sustained and transient components of the FFR are differentially affected by age, and (3) determine if the inability to encode a simple signal predicts degradation in representation for complex speech signals. Research Design: Correlational Study Sample: Thirty four adults (aged 22-77 yr) with hearing thresholds falling within normal limits. Data Collection and Analysis: Stimuli used to evoke FFRs were 1000 Hz tone bursts as well as a consonant-vowel /da/ sound. Results: The neural representation of simple (tone) and complex (/da/) stimuli declines with advancing age. Tone-FFR phase coherence decreased as chronological age increased. For the consonant-vowel FFRs, transient onset and offset response amplitudes were smaller, and offset responses were delayed with age. Sustained responses at the onset of vowel periodicity were prolonged in latency and smaller in amplitude as age increased. FFT amplitude of the consonant-vowel FFR fundamental frequency did not significantly decline with increasing age. The ability to encode a simple signal was related to degradation in the neural representation of a complex, speechlike sound. Tone-FFR phase coherence was significantly related to the later vowel response components but not the earlier vowel components. Conclusions: FFR components representing the tone and consonant-vowel /da/ stimulus were negatively affected by age, showing age-related reductions in response synchrony and amplitude, as well as prolonged latencies. These aging effects were evident in middle age, even in the absence of significant hearing loss. [ABSTRACT FROM AUTHOR]

Abstract Objective: There is interest in using cortical auditory evoked potentials (CAEPs) to evaluate hearing aid fittings and experience-related plasticity associated with amplification; however, little is known about hearing aid signal processing effects on these responses. The purpose of this study was to determine the effect of clinically relevant hearing aid gain settings, and the resulting in-the-canal signal-to-noise ratios (SNRs), on the latency and amplitude of P1, N1, and P2 waves. Design & Sample: Evoked potentials and in-the-canal acoustic measures were recorded in nine normal-hearing adults in unaided and aided conditions. In the aided condition, a 40-dB signal was delivered to a hearing aid programmed to provide four levels of gain (0, 10, 20, and 30 dB). As a control, unaided stimulus levels were matched to aided condition outputs (i.e. 40, 50, 60, and 70 dB) for comparison purposes. Results: When signal levels are defined in terms of output level, aided CAEPs were surprisingly smaller and delayed relative to unaided CAEPs, probably resulting from increases to noise levels caused by the hearing aid. Discussion: These results reinforce the notion that hearing aids modify stimulus characteristics such as SNR, which in turn affects the CAEP in a way that does not reliably reflect hearing aid gain. Sumario Objetivo: Existe interéés en el uso de los potenciales evocados auditivos corticales (CAEP) para evaluar la adaptacióón de auxiliares auditivos y la plasticidad relacionada con la experiencia, asociada a la amplificacióón; no obstante, se sabe poco sobre los efectos del procesamiento de las seññales de los auxiliares auditivos sobre esas respuestas. El propóósito de esta investigacióón fue determinar el efecto clíínicamente relevante de los ajustes de ganancia de auxiliares auditivos y las relaciones seññal/ruido (SNR) resultantes en el conducto auditivo, sobre la latencia y la amplitud de las ondas P1, N1 y P2. Diseñño y muestra: Se registraron en nueve adultos normoyentes los potenciales evocados y las mediciones acúústicas en el conducto auditivo externo en condiciones de amplificacióón o sin ella. En la primera condicion, se envióó una seññal de 40-dB al auxiliar auditivo programado para proveer cuatro niveles de ganancia (0, 10, 20 y 30 dB). Como control, se parearon niveles de estíímulos sin amplificacióón con las salidas de los estíímulos amplificados (p.ej., 40, 50, 60 y 70 dB) para efectos comparativos. Resultados: Cuando los niveles de la seññal estáán definidos en téérminos de niveles de salida, los CAEP con amplificacióón fueron sorprendentemente menores y tardííos que los CAEP sin amplificacióón, probablemente como resultado de los incrementos en los niveles de ruido, causados por el auxiliar auditivo. Discusion: Estos resultados refuerzan la idea de que los auxiliares auditivos modifican las caracteríísticas de los estíímulos como la SNR, la cual a su vez afecta los CAEP en una forma que no refleja confiablemente la ganancia del auxiliar auditivo. [ABSTRACT FROM AUTHOR]

Abstract: Older adults, even with clinically normal hearing sensitivity, have auditory perceptual deficits relative to their younger counterparts. This difficulty may in part, be related to a decline in the neural representation of frequency. The purpose of this study was to examine the effect of age on behavioral and physiological measures of frequency representation. Thirty two adults (ages 22–77), with hearing thresholds ⩽25dB HL at octave frequencies 0.25–8.0kHz, participated in this experiment. Frequency discrimination difference limens (FDLs) were obtained at 500 and 1000Hz using a two-interval, two-alternative forced choice procedure. Linear regression analyses showed significant declines in FDLs at both frequencies as age increased. Frequency-following responses (FFRs) were elicited by 500 and 1000Hz tonebursts, as well as at frequencies within and outside those FDLs. Linear regression of FFR phase coherence and FFR amplitude at frequencies at and slightly below 1000Hz showed significant decreases as age increased. Therefore, pitch discrimination, as measured by FDLs, and neural representation of frequency, as reflected by FFR, declined as age increased. Although perception and neural representation concurrently declined, one was not predictive of the other. [Copyright &y& Elsevier]

Auditory training programs are being developed to remediate various types of communication disorders. Biological changes have been shown to coincide with improved perception following auditory training so there is interest in determining if these changes represent biologic markers of auditory learning. Here we examine the role of stimulus exposure and listening tasks, in the absence of training, on the modulation of evoked brain activity. Twenty adults were divided into two groups and exposed to two similar sounding speech syllables during four electrophysiological recording sessions (24 hours, one week, and up to one year later). In between each session, members of one group were asked to identify each stimulus. Both groups showed enhanced neural activity from session-to-session, in the same P2 latency range previously identified as being responsive to auditory training. The enhancement effect was most pronounced over temporal-occipital scalp regions and largest for the group who participated in the identification task. The effects were rapid and long-lasting with enhanced synchronous activity persisting months after the last auditory experience. Physiological changes did not coincide with perceptual changes so results are interpreted to mean stimulus exposure, with and without being paired with an identification task, alters the way sound is processed in the brain. The cumulative effect likely involves auditory memory; however, in the absence of training, the observed physiological changes are insufficient to result in changes in learned behavior. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this study was to determine the effect of signal level and signal-to-noise ratio (SNR) on the latency and amplitude of evoked cortical activity to further our understanding of how the human central auditory system encodes signals in noise. Cortical auditory evoked potentials (CAEPs) were recorded from 15 young normal-hearing adults in response to a 1000Hz tone presented at two tone levels in quiet and while continuous background noise levels were varied in five equivalent SNR steps. These 12 conditions were used to determine the effects of signal level and SNR level on CAEP components P1, N1, P2, and N2. Based on prior signal-in-noise experiments conducted in animals, we hypothesized that SNR, would be a key contributor to human CAEP characteristics. As hypothesized, amplitude increased and latency decreased with increasing SNR; in addition, there was no main effect of tone level across the two signal levels tested (60 and 75dB SPL). Morphology of the P1–N1–P2 complex was driven primarily by SNR, highlighting the importance of noise when recording CAEPs. Results are discussed in terms of the current interest in recording CAEPs in hearing aid users. [Copyright &y& Elsevier]

Abstract: Objective: Auditory training alters neural activity in humans but it is unknown if these alterations are specific to the trained cue. The objective of this study was to determine if enhanced cortical activity was specific to the trained voice-onset-time (VOT) stimuli ‘mba’ and ‘ba’, or whether it generalized to the control stimulus ‘a’ that did not contain the trained cue. Methods: Thirteen adults were trained to identify a 10ms VOT cue that differentiated the two experimental stimuli. We recorded event-related potentials (ERPs) evoked by three different speech sounds ‘ba’ ‘mba’ and ‘a’ before and after six days of VOT training. Results: The P2 wave increased in amplitude after training for both control and experimental stimuli, but the effects differed between stimulus conditions. Whereas the effects of training on P2 amplitude were greatest in the left hemisphere for the trained stimuli, enhanced P2 activity was seen in both hemispheres for the control stimulus. In addition, subjects with enhanced pre-training N1 amplitudes were more responsive to training and showed the most perceptual improvement. Conclusion: Both stimulus-specific and general effects of training can be measured in humans. An individual’s pre-training N1 response might predict their capacity for improvement. Significance: N1 and P2 responses can be used to examine physiological correlates of human auditory perceptual learning. [Copyright &y& Elsevier]

Hearing aid amplification can be used as a model for studying the effects of auditory stimulation on the central auditory system (CAS). We examined the effects of stimulus presentation level on the physiological detection of sound in unaided and aided conditions. P1, N1, P2, and N2 cortical evoked potentials were recorded in sound field from 13 normal-hearing young adults in response to a 1000-Hz tone presented at seven stimulus intensity levels. As expected, peak amplitudes increased and peak latencies decreased with increasing intensity for unaided and aided conditions. However, there was no significant effect of amplification on latencies or amplitudes. Taken together, these results demonstrate that 20 dB of hearing aid gain affects neural responses differently than 20 dB of stimulus intensity change. Hearing aid signal processing is discussed as a possible contributor to these results. This study demonstrates (1) the importance of controlling for stimulus intensity when evoking responses in aided conditions, and (2) the need to better understand the interaction between the hearing aid and the CAS. [ABSTRACT FROM AUTHOR]

Auditory evoked cortical responses to changes in the interaural phase difference (IPD) were recorded using magnetoencephalography (MEG). Twelve normal-hearing young adults were tested with amplitude-modulated tones with carrier frequencies of 500, 1000, 1250, and 1500 Hz. The onset of the stimuli evoked P1m-N1m-P2m cortical responses, as did the changes in the interaural phase. Significant responses to IPD changes were identified at 500 and 1000 Hz in all subjects and at 1250 Hz in nine subjects, whereas responses were absent in all subjects at 1500 Hz, indicating a group mean threshold for detecting IPDs of 1250 Hz. Behavioral thresholds were found at 1200 Hz using an adaptive two alternative forced choice procedure. Because the physiological responses require phase information, through synchronous bilateral inputs at the level of the auditory brainstem, physiological “change” detection thresholds likely reflect the upper limit of phase synchronous activity in the brainstem. The procedure has potential applications in investigating impaired binaural processing because phase statistic applied to single epoch MEG data allowed individual thresholds to be obtained. [ABSTRACT FROM AUTHOR]

We examined the effects of stimulus complexity and stimulus presentation rate in ten younger and ten older normal-hearing adults. A 1 kHz tone burst as well as a speech syllable were used to elicit the N1-P2 complex. Three different interstimulus intervals (ISI) were used (510, 910, and 1510 msec), When stimuli were presented at the medium presentation rate (910 msec ISI), N1 and P2 latencies were prolonged for older listeners in response to the speech stimulus but not the tone stimulus. These age effects were absent when stimuli were presented at a slower rate (1510 msec ISI). Results from this study suggest that rapidly occurring stimulus onsets, either within a stimulus or between stimuli, result in prolonged N1 and P2 responses in older adults. This is especially true when processing complex stimuli such as speech. One potential explanation for this age effect might be age-related refractory differences in younger and older auditory systems. Refractory issues might in turn affect synchronized neural activity underlying the perception of critical time-varying speech cues and may partially explain some of the difficulties older people experience understanding speech. [ABSTRACT FROM AUTHOR]

A recurring problem in aging research is separating the effects of age per se from the effects of high-frequency hearing loss. One approach is to present test stimuli in the presence of a high-pass masker to control confounding differences in high-frequency audibility across age groups. However, there is evidence that such maskers may affect older and younger listeners differently. In this study, pure-tone thresholds were measured for younger and older listeners in the presence of high-pass maskers. The age groups were carefully selected based on similar unmasked thresholds at each frequency. Thresholds were measured in quiet and in seven masker conditions. Both younger and older listeners showed increased threshold shift below the masker passband as the masker level increased. The degree of threshold shift was not greater for older versus younger listeners. Results suggest that high-pass maskers may be used to reduce high-frequency sensitivity differences between younger and older listeners without introducing differential masking effects. [ABSTRACT FROM AUTHOR]

Objective: To examine the effects of aging and age-related hearing loss on the perception and neural representation of a time-varying speech cue.Methods: P1, N1 and P2 cortical responses were recorded from younger and older normal-hearing adults, as well as older adults with age-related hearing loss. Synthetic speech tokens representing 10 ms increments along a /ba/–/pa/ voice-onset-time (VOT) continuum were used to evoke the responses. Each participant''s ability to discriminate the speech tokens was also assessed.Results: Compared with younger participants, older adults with and without hearing loss had more difficulty discriminating 10 ms VOT contrasts. In addition, both older groups elicited abnormal neural response patterns. There were no significant age-related findings for P1 latency; however, N1 latencies were prolonged for both older groups in response to stimuli with increased VOT durations. Also, P2 latencies were delayed for both older groups. The presence of age-related hearing loss resulted in a significant increase in N1 amplitude in response to voiceless stimuli.Conclusions: Aging and age-related hearing loss alter temporal response properties in the central auditory system. Because both older groups had difficulty discriminating these same speech stimuli, we conclude that some of the perceptual difficulties described by older adults might be due to age-related changes regulating excitatory and inhibitory processes.Significance: Some of the speech understanding difficulties expressed by elderly adults may be related to impaired temporal precision in the aging auditory system. This might explain why older adults frequently complain that wearing a hearing aid makes speech louder, but does not necessarily improve their ability to understand speech. [Copyright &y& Elsevier]

Pre-attentive cortical evoked potentials reflect training-induced changes in neural activity associated with speech-sound training. Seven normal-hearing young adults were trained to identify two synthetic speech variants of the syllable /ba/. As subjects learned to correctly identify the two stimuli, changes in P1, N1, and P2 amplitudes were observed. Of particular interest is that P1, N1, and P2 components of the N1-P2 complex responded differently to listening training. That is, significant changes in P1 and N1 amplitude were recorded over the right but not the left hemisphere. In contrast, increases in P2 were observed bilaterally. These results indicate that training-related changes in neural activity are reflected in far-field aggregate neural responses and that distinct patterns of neural change, perhaps reflecting hemispheric specialization, likely represent different aspects of auditory function. [ABSTRACT FROM AUTHOR]

The frequency-following response with origin in the auditory brainstem represents the pitch contour of voice and can be recorded with electrodes from the scalp. MEG studies also revealed a cortical contribution to the high gamma oscillations at the fundamental frequency (f 0) of a vowel stimulus. Therefore, studying the cortical component of the frequency-following response could provide insights into how pitch information is encoded at the cortical level. Comparing how aging affects the different responses may help to uncover the neural mechanisms underlying speech understanding deficits in older age. We simultaneously recorded EEG and MEG responses to the syllable /ba/. MEG beamformer analysis localized sources in bilateral auditory cortices and the midbrain. Time-frequency analysis showed a faithful representation of the pitch contour between 106 Hz and 138 Hz in the cortical activity. A cross-correlation revealed a latency of 20 ms. Furthermore, stimulus onsets elicited cortical 40-Hz responses. Both the 40-Hz and the f 0 response amplitudes increased in older age and were larger in the right hemisphere. The effects of aging and laterality of the f 0 response were evident in the MEG only, suggesting that both effects were characteristics of the cortical response. After comparing f 0 and N1 responses in EEG and MEG, we estimated that approximately one-third of the scalp-recorded f 0 response could be cortical in origin. We attributed the significance of the cortical f 0 response to the precise timing of cortical neurons that serve as a time-sensitive code for pitch. Image 1 • MEG source activity reveals cortical gamma oscillations phase-locked to vocal pitch. • High-frequency oscillation control precise timing for a cortical neural code of pitch. • Vocal pitch and 40-Hz gamma responses are right lateralized and increase in older age. • Simultaneous EEG and MEG allow estimating subcortical and cortical contributions. [ABSTRACT FROM AUTHOR]

Background: The projected increase in the aging population raises concerns about how to manage the health-care needs in a cost-effective way. Within hearing health care, there are presently too few audiologists to meet the expected demand, and training more professionals may not be a feasible way of addressing this problem. For this reason, there is a need to develop different ways of assessing hearing sensitivity that can be conducted accurately and inexpensively when a certified audiologist and/or sound-attenuated booth is unavailable. More specifically, there is a need to determine if the Etymotic Home Hearing Test (HHT) can yield accurate and reliable data from older adults with varying degrees of hearing loss. Purpose: To compare audiometric thresholds obtained using the HHT, an automated pure-tone air-conduction test, to those obtained using manual audiometry (MA), among older adults with varying degrees of hearing loss. Study Sample: Participants were 112 English-speaking adults (58% Female), aged 60 yr and older. Participants were excluded from this study if otoscopy revealed cerumen impaction and/or suspected ear pathology. Intervention: All participants completed the HHT on tablet computers in a carpeted classroom and MA in a double-walled sound-attenuated booth using insert earphones for both measures. Both measures were completed in the same test session, and the order of testing (MA versus HHT) was counterbalanced. Data Collection and Analysis: Absolute differences in threshold measurements (in dB HL) were calculated across all ears (n = 224 ears) and for all frequencies (octave frequencies from 0.5 to 8 kHz). Correlation and multiple linear regression analyses were conducted to determine if thresholds obtained using the HHT significantly correlated with thresholds using MA. Mean thresholds for each method (HHT and MA) were compared using correlation analyses for each test frequency. Multiple linear regression analysis was used to examine the relationship between the four-frequency pure-tone average (PTA) (average threshold at 0.5, 1, 2, and 4 kHz) in the better-hearing ear measured using the HHT and a set of seven independent factors: four-frequency PTA in the better-hearing ear measured via MA, treatment group (HHT versus MA), age, gender, and degree of hearing loss (mild, moderate, and >moderate). Results: Correlation analyses revealed significant frequency-specific correlations, ranging from 0.91 to 0.97 (p < 0.001), for air-conduction thresholds obtained using the HHT and MA. Mean HHT thresholds were significantly correlated with mean MA thresholds in both ears across the frequency range. This relationship held true across different degrees of hearing loss. The regression model accounted for a significant amount of variance in the HHT better-ear PTA, with MA better-ear PTA being the only significant predictor in our final model, with no effect of degree of loss, age, or gender. Conclusions: The HHT is an accurate and cost-effective method of establishing pure-tone air-conduction thresholds, when compared with MA. Therefore, the HHT can be used as a tool to acquire accurate air-conduction hearing thresholds from older adults, in-group settings, without the use of a sound-attenuated booth or a certified audiologist. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including the challenges that can be faced when recording brain activity in people who wear hearing aids, various cognitive processes involved in making use of audible sound and the challenges faced by everyday users of hearing aids.

Background Auditory perceptual learning persistently modifies neural networks in the central nervous system. Central auditory processing comprises a hierarchy of sound analysis and integration, which transforms an acoustical signal into a meaningful object for perception. Based on latencies and source locations of auditory evoked responses, we investigated which stage of central processing undergoes neuroplastic changes when gaining auditory experience during passive listening and active perceptual training. Young healthy volunteers participated in a five-day training program to identify two pre-voiced versions of the stop-consonant syllable 'ba', which is an unusual speech sound to English listeners. Magnetoencephalographic (MEG) brain responses were recorded during two pre-training and one post-training sessions. Underlying cortical sources were localized, and the temporal dynamics of auditory evoked responses were analyzed. Results After both passive listening and active training, the amplitude of the P2m wave with latency of 200 ms increased considerably. By this latency, the integration of stimulus features into an auditory object for further conscious perception is considered to be complete. Therefore the P2m changes were discussed in the light of auditory object representation. Moreover, P2m sources were localized in anterior auditory association cortex, which is part of the anteroventral pathway for object identification. The amplitude of the earlier N1m wave, which is related to processing of sensory information, did not change over the time course of the study. Conclusion The P2m amplitude increase and its persistence over time constitute a neuroplastic change. The P2m gain likely reflects enhanced object representation after stimulus experience and training, which enables listeners to improve their ability for scrutinizing fine differences in pre-voicing time. Different trajectories of brain and behaviour changes suggest that the preceding effect of a P2m increase relates to brain processes, which are necessary precursors of perceptual learning. Cautious discussion is required when interpreting the finding of a P2 amplitude increase between recordings before and after training and learning. [ABSTRACT FROM AUTHOR]

Performance improvement during an hour of auditory perceptual training is accompanied by rapid physiological changes. These changes may reflect learning or simply task repetition independent of learning. We assessed the contribution of learning and task repetition to changes in auditory evoked potentials during a difficult speech identification task and an easy tone identification task. We posited that only task repetition effects would occur in the tone task but that task repetition and learning would interact in the speech task. Speech identification improved with practice (increased sensitivity d′ with a constant response bias β). This behavioral improvement coincided with a decrease in the amplitude of sensory evoked responses (N1, P2) and a decrease in the amplitude of a slow wave (peak=320 ms after onset) over the left frontal and parietal sites. Results show rapid physiological changes associated with learning, distinct from changes related to task repetition. [ABSTRACT FROM AUTHOR]

Sensory abilities decline with age. More than 5% of the world's population, approximately 360 million people, have disabling hearing loss. In adults, disabling hearing loss is defined by thresholds greater than 40 dBHL in the better hearing ear. Hearing disability is an important issue in geriatric medicine because it is associated with numerous health issues, including accelerated cognitive decline, depression, increased risk of dementia, poorer balance, falls, hospitalizations, and early mortality. There are also social implications, such as reduced communication function, social isolation, loss of autonomy, impaired driving ability, and financial decline. Furthermore, the onset of hearing loss is gradual and subtle, first affecting the detection of high-pitched sounds and with difficulty understanding speech in noisy but not in quiet environments. Consequently, delays in recognizing and seeking help for hearing difficulties are common. Age-related hearing loss has no known cure, and technologies (hearing aids, cochlear implants, and assistive devices) improve thresholds but do not restore hearing to normal. Therefore, health care for persons with hearing loss and people within their communication circles requires education and counseling (e.g., increasing knowledge, changing attitudes, and reducing stigma), behavior change (e.g., adapting communication strategies), and environmental modifications (e.g., reducing noise). In this article, we consider the causes, consequences, and magnitude of hearing loss from a life-course perspective. We examine the concept of “hearing health,” how to achieve it, and implications for policy and practice. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated (a) the effect of amplification on cortical auditory evoked potentials (CAEPs) at different signal levels when signal-to-noise ratios (SNRs) were equated between unaided and aided conditions, and (b) the effect of absolute signal level on aided CAEPs when SNR was held constant. Method: CAEPs were recorded from 13 young adults with normal hearing. A 1000-Hz pure tone was presented in unaided and aided conditions with a linear analog hearing aid. Direct audio input was used, allowing recorded hearing aid noise floor to be added to unaided conditions to equate SNRs between conditions. An additional stimulus was created through scaling the noise floor to study the effect of signal level. Results: Amplification resulted in delayed N1 and P2 peak latencies relative to the unaided condition. An effect of absolute signal level (when SNR was constant) was present for aided CAEP area measures, such that larger area measures were found at higher levels. Conclusion: Results of this study further demonstrate that factors in addition to SNR must also be considered before CAEPs can be used to clinically to measure aided thresholds. [ABSTRACT FROM AUTHOR]

Older adults often have difficulty understanding speech in a noisy environment or with multiple speakers. In such situations, binaural hearing improves the signal-to-noise ratio. How does this binaural advantage change with increasing age? Using magnetoencephalography, we recorded cortical activity evoked by changes in interaural phase differences of amplitude-modulated tones. These responses occurred for frequencies up to 1225 Hz in young subjects but only up to 940 Hz in middle-aged and 760 Hz in older adults. Behavioral thresholds also decreased with increasing age but were more variable, likely because some older adults make effective use of compensatory mechanisms. The reduced frequency range for binaural hearing became significant in middle age, before decline in hearing sensation and the morphology of cortical responses, which became apparent only in the older subjects. This study provides evidence from human physiological data for the early onset of biological aging in binaural hearing. [ABSTRACT FROM AUTHOR]