Cross-modal re-organization in adults with early stage hearing loss

Reduced Visual-Cortex Reorganization Before and After Cochlear Implantation Relates to Better Speech Recognition Ability

Although a cochlear implant (CI) can partially restore auditory function, CI recipients show alterations not only in auditory but also in visual cortical processing. Yet, it is not well understood how these visual changes relate to the CI outcome and to what extent these changes are induced by auditory deprivation and the limited CI input, respectively. Here, we present a prospective longitudinal electroencephalography study which examined the deprivation- and CI-induced alterations on cortical face processing by comparing visual evoked potentials (VEP) in CI users before and 6 months after implantation. A group of normal-hearing (NH) listeners served as a control. The participants performed a word-identification task and a face-categorization task to study the cortical processing of static and articulating faces in attended and unattended conditions. The CI candidates and CI users showed a reduced visual-cortex activation, a stronger functional connectivity between the visual and auditory cortex, and a reduced attention effect in the (extended) alpha frequency range (8-18 Hz) when compared to NH listeners. There was a positive correlation between the P1 VEP amplitude recorded before implantation and the speech recognition ability after implantation. Our results suggest that the CI users' alterations in cortical face processing are mainly induced by auditory deprivation and not by CI experience. Importantly, these deprivation-induced changes seem to be related to the CI outcome. Our results suggest that the visual P1 amplitude as recorded before implantation provides an objective index of cortical visual reorganization that may help predict the CI outcome.

Unimodal speech perception predicts stable individual differences in audiovisual benefit for phonemes, words and sentencesa)

There are substantial individual differences in the benefit that can be obtained from visual cues during speech perception. Here, 113 normally hearing participants between the ages of 18 and 60 years old completed a three-part experiment investigating the reliability and predictors of individual audiovisual benefit for acoustically degraded speech. Audiovisual benefit was calculated as the relative intelligibility (at the individual-level) of approximately matched (at the group-level) auditory-only and audiovisual speech for materials at three levels of linguistic structure: meaningful sentences, monosyllabic words, and consonants in minimal syllables. This measure of audiovisual benefit was stable across sessions and materials, suggesting that a shared mechanism of audiovisual integration operates across levels of linguistic structure. Information transmission analyses suggested that this may be related to simple phonetic cue extraction: sentence-level audiovisual benefit was reliably predicted by the relative ability to discriminate place of articulation at the consonant-level. Finally, whereas unimodal speech perception was related to cognitive measures (matrix reasoning and vocabulary) and demographics (age and gender), audiovisual benefit was predicted only by unimodal speech perceptual abilities: Better lipreading ability and subclinically poorer hearing (speech reception thresholds) independently predicted enhanced audiovisual benefit. This work has implications for practices in quantifying audiovisual benefit and research identifying strategies to enhance multimodal communication in hearing loss.

Visual Cortical Processing in Children with Early Bilateral Cochlear Implants: A VEP Analysis

BACKGROUND/OBJECTIVES

Cochlear implantation is the primary treatment for severe-to-profound hearing loss, yet outcomes vary significantly among recipients. While visual-auditory cross-modal reorganization has been identified as a contributing factor to this variability, its impact in early-implanted children remains unclear. To address this knowledge gap, we investigated visual processing and its relationship with auditory outcomes in children who received early bilateral cochlear implants.

METHODS

To examine potential cross-modal reorganization, we recorded visual evoked potentials (VEPs) in response to pattern-reversal stimuli in 25 children with cochlear implants (CIs) (mean implantation age: 1.44 years) and 28 age-matched normal-hearing (NH) controls. Analysis focused on both the occipital region of interest (ROI: O1, OZ, and O2 electrode sites) and right temporal ROI, examining VEP components and their correlation with speech perception outcomes.

RESULTS

Unlike previous studies in later-implanted children, the overall occipital ROI showed no significant differences between groups. However, the left occipital electrode (O1) revealed reduced P1 amplitudes and delayed N1 latencies in CI users. Importantly, O1 N1 latency negatively correlated with speech-in-noise performance (r = -0.318; p = 0.02). The right temporal region showed no significant differences in VEP N1 between groups and no correlation with speech performance in CI users.

CONCLUSIONS

Early bilateral cochlear implantation appears to preserve global visual processing, suggesting minimal maladaptive reorganization. However, subtle alterations in left occipital visual processing may influence auditory outcomes, highlighting the importance of early intervention and the complex nature of sensory integration in this population.

Speech outcomes in cochlear implant users depend on visual cross-modal cortical activity measured before or after implantation

Cochlear implants can partially restore hearing function in deaf individuals, but long-term speech listening outcomes vary widely across cochlear implant users. Visual cross-modal plasticity, where auditory cortical neurons upregulate visual inputs to assist visual processing, is one factor proposed to worsen cochlear implant users' speech outcomes because it may limit auditory processing capability. However, evidence for this view is conflicting, and the relationship of cross-modal activity to speech perception may depend on other variables such as the type of visual activity and when it is assessed. To clarify, we measured visual cross-modal activity during a silent lip reading task using EEG in a cross-sectional, observational study. The study tested visual brain activation in 14 individuals prior to receiving a cochlear implant, 15 individuals tested at least 1 year after receiving and using a cochlear implant and 13 typical hearing controls who did not use a cochlear implant or hearing aid. Cross-modal responses to the onset of a visual event were positively correlated to speech outcomes in cochlear implant users tested after surgery but were negatively correlated in those tested prior to cochlear implant surgery. In addition, cross-modal increases in neural oscillatory power in the alpha band (8-12 Hz) arising in the lip reading task were associated with worse speech outcomes in both cochlear implant user groups. Taken together, results redress claims that cross-modal plasticity is maladaptive for speech outcomes and instead suggest that this relationship depends on the time point of testing, stage of sensory processing and likely the relevance of the stimulus for speech. In addition, findings form the basis for new neural markers that are predictive of cochlear implant users' long-term speech ability.

Does experience with hearing aid amplification influence electrophysiological measures of speech comprehension?

OBJECTIVE

To explore if experience with hearing aid (HA) amplification affects speech-evoked cortical potentials reflecting comprehension abilities.

DESIGN

N400 and late positive complex (LPC) responses as well as behavioural response times to congruent and incongruent digit triplets were measured. The digits were presented against stationary speech-shaped noise 10 dB above individually measured speech recognition thresholds. Stimulus presentation was either acoustic (digits 1-3) or first visual (digits 1-2) and then acoustic (digit 3).

STUDY SAMPLE

Three groups of older participants (N = 3 × 15) with (1) pure-tone average hearing thresholds <25 dB HL from 500-4000 Hz, (2) mild-to-moderate sensorineural hearing loss (SNHL) but no prior HA experience, and (3) mild-to-moderate SNHL and >2 years of HA experience. Groups 2-3 were fitted with test devices in accordance with clinical gain targets.

RESULTS

No group differences were found in the electrophysiological data. N400 amplitudes were larger and LPC latencies shorter with acoustic presentation. For group 1, behavioural response times were shorter with visual-then-acoustic presentation.

CONCLUSION

When speech audibility is ensured, comprehension-related electrophysiological responses appear intact in individuals with mild-to-moderate SNHL, regardless of prior experience with amplified sound. Further research into the effects of audibility versus acclimatisation-related neurophysiological changes is warranted.

Cross-Modal Plasticity in Postlingual Hearing Loss Predicts Speech Perception Outcomes After Cochlear Implantation

Background: Sensory loss may lead to intra- and cross-modal cortical reorganization. Previous research showed a significant correlation between the cross-modal contribution of the right auditory cortex to visual evoked potentials (VEP) and speech perception in cochlear implant (CI) users with prelingual hearing loss (HL), but not in those with postlingual HL. The present study aimed to explore the cortical reorganization induced by postlingual HL, particularly in the right temporal region, and how it correlates with speech perception outcome with a CI. Material and Methods: A total of 53 adult participants were divided into two groups according to hearing ability: 35 had normal hearing (NH) (mean age = 62.10 years (±7.48)) and 18 had profound postlingual HL (mean age = 63.78 years (±8.44)). VEPs, using a 29-channel electroencephalogram (EEG) system, were recorded preoperatively in the 18 patients scheduled for cochlear implantation and in 35 NH adults who served as the control group. Amplitudes and latencies of the P100, N100, and P200 components were analyzed across frontal, temporal, and occipital areas and compared between NH and HL subjects using repeated measures ANOVA. For the HL group, speech perception in quiet was assessed at 6 and 12 months of CI use. Results: No difference was found in amplitudes or latencies of the P100, N100, and P200 VEP components between the NH and HL groups. Further analysis using Spearman correlations between preoperative amplitudes and latencies of the P100, N100, and P200 VEP components at the right temporal electrode position T8 and postoperative speech perception showed that the HL group had either significantly higher or significantly lower amplitudes of the P200 component at the right temporal electrode position T8 compared to the NH controls. The HL subgroup with higher amplitudes had better speech perception than the subgroup with lower amplitudes at 6 months and 12 months of CI use. Conclusions: Preoperative evaluation of cortical plasticity can reveal plasticity profiles, which might help to better predict postoperative speech outcomes and adapt the rehabilitation regimen after CI activation. Further research is needed to understand the susceptibility of each component to cross-modal reorganization and their specific contribution to outcome prediction.

Cortical region-specific recovery of auditory temporal processing following noise-induced hearing loss

Noise-induced hearing loss (NIHL) studies have focused on the lemniscal auditory pathway, but little is known about how NIHL impacts different cortical regions. Here we compared response recovery trajectories in the auditory and frontal cortices (AC, FC) of mice following NIHL. We recorded EEG responses from awake mice (male n = 15, female n = 14) before and following NIHL (longitudinal design) to quantify event related potentials and gap-in-noise temporal processing. Hearing loss was verified by measuring the auditory brainstem response (ABR) before and at 1-, 10-, 23-, and 45-days after noise-exposure. Resting EEG, event related potentials (ERP) and auditory steady state responses (ASSR) were recorded at the same time-points after NIHL. The inter-trial phase coherence (ITPC) of the ASSR was measured to quantify the ability of AC and FC to synchronize responses to short gaps embedded in noise. Despite the absence of click-evoked ABRs up to 90 dB SPL and up to 45-days post-exposure, ERPs from the AC and FC showed full recovery in ∼ 50 % of the mice to pre-NIHL levels in both AC and FC. The ASSR ITPC was reduced following NIHL in AC and FC in all the mice on day 1 after NIHL. The AC showed full recovery of ITPC over 45-days. Despite ERP amplitude recovery, the FC does not show recovery of ASSR ITPC. These results indicate post-NIHL plasticity with similar response amplitude recovery across AC and FC, but cortical region-specific trajectories in temporal processing recovery.

Neuroplasticity of Speech-in-Noise Processing in Older Adults Assessed by Functional Near-Infrared Spectroscopy (fNIRS)

Functional near-infrared spectroscopy (fNIRS), a non-invasive optical neuroimaging technique that is portable and acoustically silent, has become a promising tool for evaluating auditory brain functions in hearing-vulnerable individuals. This study, for the first time, used fNIRS to evaluate neuroplasticity of speech-in-noise processing in older adults. Ten older adults, most of whom had moderate-to-mild hearing loss, participated in a 4-week speech-in-noise training. Their speech-in-noise performances and fNIRS brain responses to speech (auditory sentences in noise), non-speech (spectrally-rotated speech in noise) and visual (flashing chequerboards) stimuli were evaluated pre- (T0) and post-training (immediately after training, T1; and after a 4-week retention, T2). Behaviourally, speech-in-noise performances were improved after retention (T2 vs. T0) but not immediately after training (T1 vs. T0). Neurally, we intriguingly found brain responses to speech vs. non-speech decreased significantly in the left auditory cortex after retention (T2 vs. T0 and T2 vs. T1) for which we interpret as suppressed processing of background noise during speech listening alongside the significant behavioural improvements. Meanwhile, functional connectivity within and between multiple regions of temporal, parietal and frontal lobes was significantly enhanced in the speech condition after retention (T2 vs. T0). We also found neural changes before the emergence of significant behavioural improvements. Compared to pre-training, responses to speech vs. non-speech in the left frontal/prefrontal cortex were decreased significantly both immediately after training (T1 vs. T0) and retention (T2 vs. T0), reflecting possible alleviation of listening efforts. Finally, connectivity was significantly decreased between auditory and higher-level non-auditory (parietal and frontal) cortices in response to visual stimuli immediately after training (T1 vs. T0), indicating decreased cross-modal takeover of speech-related regions during visual processing. The results thus showed that neuroplasticity can be observed not only at the same time with, but also before, behavioural changes in speech-in-noise perception. To our knowledge, this is the first fNIRS study to evaluate speech-based auditory neuroplasticity in older adults. It thus provides important implications for current research by illustrating the promises of detecting neuroplasticity using fNIRS in hearing-vulnerable individuals.

Investigation of Deficits in Auditory Emotional Content Recognition by Adult Cochlear Implant Users through the Study of Electroencephalographic Gamma and Alpha Asymmetry and Alexithymia Assessment

BACKGROUND/OBJECTIVES

Given the importance of emotion recognition for communication purposes, and the impairment for such skill in CI users despite impressive language performances, the aim of the present study was to investigate the neural correlates of emotion recognition skills, apart from language, in adult unilateral CI (UCI) users during a music in noise (happy/sad) recognition task. Furthermore, asymmetry was investigated through electroencephalographic (EEG) rhythm, given the traditional concept of hemispheric lateralization for emotional processing, and the intrinsic asymmetry due to the clinical UCI condition.

METHODS

Twenty adult UCI users and eight normal hearing (NH) controls were recruited. EEG gamma and alpha band power was assessed as there is evidence of a relationship between gamma and emotional response and between alpha asymmetry and tendency to approach or withdraw from stimuli. The TAS-20 questionnaire (alexithymia) was completed by the participants.

RESULTS

The results showed no effect of background noise, while supporting that gamma activity related to emotion processing shows alterations in the UCI group compared to the NH group, and that these alterations are also modulated by the etiology of deafness. In particular, relative higher gamma activity in the CI side corresponds to positive processes, correlated with higher emotion recognition abilities, whereas gamma activity in the non-CI side may be related to positive processes inversely correlated with alexithymia and also inversely correlated with age; a correlation between TAS-20 scores and age was found only in the NH group.

CONCLUSIONS

EEG gamma activity appears to be fundamental to the processing of the emotional aspect of music and also to the psychocognitive emotion-related component in adults with CI.

Neurocognitive outcomes in young adults with cochlear implants: The role of early language access and crossmodal plasticity

Many children with profound hearing loss have received cochlear implants (CI) to help restore some sense of hearing. There is, however, limited research on long-term neurocognitive outcomes in young adults who have grown up hearing through a CI. This study compared the cognitive outcomes of early-implanted (n = 20) and late-implanted (n = 21) young adult CI users, and typically hearing (TH) controls (n=56), all of whom were enrolled in college. Cognitive fluidity, nonverbal intelligence, and American Sign Language (ASL) comprehension were assessed, revealing no significant differences in cognition and nonverbal intelligence between the early and late-implanted groups. However, there was a difference in ASL comprehension, with the late-implanted group having significantly higher ASL comprehension. Although young adult CI users showed significantly lower scores in a working memory and processing speed task than TH age-matched controls, there were no significant differences in tasks involving executive function shifting, inhibitory control, and episodic memory between young adult CI and young adult TH participants. In an exploratory analysis of a subset of CI participants (n = 17) in whom we were able to examine crossmodal plasticity, we saw greater evidence of crossmodal recruitment from the visual system in late-implanted compared with early-implanted CI young adults. However, cortical visual evoked potential latency biomarkers of crossmodal plasticity were not correlated with cognitive measures or ASL comprehension. The results suggest that in the late-implanted CI users, early access to sign language may have served as a scaffold for appropriate cognitive development, while in the early-implanted group early access to oral language benefited cognitive development. Furthermore, our results suggest that the persistence of crossmodal neuroplasticity into adulthood does not necessarily impact cognitive development. In conclusion, early access to language - spoken or signed - may be important for cognitive development, with no observable effect of crossmodal plasticity on cognitive outcomes.

Layer-specific enhancement of visual-evoked activity in the audiovisual cortex following a mild degree of hearing loss in adult rats

Following adult-onset hearing impairment, crossmodal plasticity can occur within various sensory cortices, often characterized by increased neural responses to visual stimulation in not only the auditory cortex, but also in the visual and audiovisual cortices. In the present study, we used an established model of loud noise exposure in rats to examine, for the first time, whether the crossmodal plasticity in the audiovisual cortex that occurs following a relatively mild degree of hearing loss emerges solely from altered intracortical processing or if thalamocortical changes also contribute to the crossmodal effects. Using a combination of an established pharmacological 'cortical silencing' protocol and current source density analysis of the laminar activity recorded across the layers of the audiovisual cortex (i.e., the lateral extrastriate visual cortex, V2L), we observed layer-specific changes post-silencing in the strength of the residual visual, but not auditory, input in the noise exposed rats with mild hearing loss compared to rats with normal hearing. Furthermore, based on a comparison of the laminar profiles pre- versus post-silencing in both groups, we can conclude that noise exposure caused a re-allocation of the strength of visual inputs across the layers of the V2L cortex, including enhanced visual-evoked activity in the granular layer; findings consistent with thalamocortical plasticity. Finally, we confirmed that audiovisual integration within the V2L cortex depends on intact processing within intracortical circuits, and that this form of multisensory processing is vulnerable to disruption by noise-induced hearing loss. Ultimately, the present study furthers our understanding of the contribution of intracortical and thalamocortical processing to crossmodal plasticity as well as to audiovisual integration under both normal and mildly-impaired hearing conditions.

P1 and N1 Characteristics in Individuals with Normal Hearing and Hearing Loss, and Cochlear Implant Users: A Pilot Study

Background: It has been reported in many previous studies that the lack of auditory input due to hearing loss (HL) can induce changes in the brain. However, most of these studies have focused on individuals with pre-lingual HL and have predominantly compared the characteristics of those with normal hearing (NH) to cochlear implant (CI) users in children. This study examined the visual and auditory evoked potential characteristics in NH listeners, individuals with bilateral HL, and CI users, including those with single-sided deafness. Methods: A total of sixteen participants (seven NH listeners, four individuals with bilateral sensorineural HL, and five CI users) completed speech testing in quiet and noise and evoked potential testing. For speech testing, the Korean version of the Hearing in Noise Test was used to assess individuals' speech understanding ability in quiet and in noise (noise from the front, +90 degrees, and -90 degrees). For evoked potential testing, visual and auditory (1000 Hz, /ba/, and /da/) evoked potentials were measured. Results: The results showed that CI users understood speech better than those with HL in all conditions except for the noise from +90 and -90 degrees. In the CI group, a decrease in P1 amplitudes was noted across all channels after implantation. The NH group exhibited the highest amplitudes, followed by the HL group, with the CI group (post-CI) showing the lowest amplitudes. In terms of auditory evoked potentials, the smallest amplitude was observed in the pre-CI condition regardless of the type of stimulus. Conclusions: To the best of our knowledge, this is the first study that examined visual and auditory evoked potentials based on various hearing profiles. The characteristics of evoked potentials varied across participant groups, and further studies with CI users are necessary, as there are significant challenges in collecting and analyzing evoked potentials due to artifact issues on the CI side.

Alpha and theta oscillations on a visual strategic processing task in age-related hearing loss

Introduction

Emerging evidence suggests changes in several cognitive control processes in individuals with age-related hearing loss (ARHL). However, value-directed strategic processing, which involves selectively processing salient information based on high value, has been relatively unexplored in ARHL. Our previous work has shown behavioral changes in strategic processing in individuals with ARHL. The current study examined event-related alpha and theta oscillations linked to a visual, value-directed strategic processing task in 19 individuals with mild untreated ARHL and 17 normal hearing controls of comparable age and education.

Methods

Five unique word lists were presented where words were assigned high- or low-value based on the letter case, and electroencephalography (EEG) data was recorded during task performance.

Results

The main effect of the group was observed in early time periods. Specifically, greater theta synchronization was seen in the ARHL group relative to the control group. Interaction between group and value was observed at later time points, with greater theta synchronization for high- versus low-value information in those with ARHL.

Discussion

Our findings provide evidence for oscillatory changes tied to a visual task of value-directed strategic processing in individuals with mild untreated ARHL. This points towards modality-independent neurophysiological changes in cognitive control in individuals with mild degrees of ARHL and adds to the rapidly growing literature on the cognitive consequences of ARHL.

The effect of hearing loss on age-related differences in neural distinctiveness

Age differences in cognitive performance have been shown to be overestimated if age-related hearing loss is not taken into account. Here, we investigated the role of age-related hearing loss on age differences in functional brain organization by assessing its impact on previously reported age differences in neural differentiation. To this end, we analyzed the data of 36 younger adults, 21 older adults with clinically normal hearing, and 21 older adults with mild-to-moderate hearing loss who had taken part in a functional localizer task comprising visual (i.e., faces, scenes) and auditory stimuli (i.e., voices, music) while undergoing functional magnetic resonance imaging. Evidence for reduced neural distinctiveness in the auditory cortex was observed only in older adults with hearing loss relative to younger adults, whereas evidence for reduced neural distinctiveness in the visual cortex was observed both in older adults with normal hearing and in older adults with hearing loss relative to younger adults. These results indicate that age-related dedifferentiation in the auditory cortex is exacerbated by age-related hearing loss.

Design and Methods of the Early Age-Related Hearing Loss Investigation Randomized Controlled Trial

OBJECTIVE

Hearing loss has been identified as a major modifiable risk factor for cognitive decline. The Early Age-Related Hearing Loss Investigation (EARHLI) study will assess the mechanisms linking early age-related hearing loss (ARHL) and cognitive impairment.

STUDY DESIGN

Randomized, controlled, single-site, early phase II, superiority trial.

SETTING

Tertiary academic medical center.

PARTICIPANTS

One hundred fifty participants aged 55 to 75 years with early ARHL (severity defined as borderline to moderate) and amnestic mild cognitive impairment will be included.

INTERVENTIONS

Participants will be randomized 1:1 to a best practice hearing intervention or a health education control.

MAIN OUTCOME MEASURES

The primary study outcome is cognition measured by the Alzheimer Disease Cooperative Study-Preclinical Alzheimer Cognitive Composite. Secondary outcomes include additional measures of cognition, social engagement, and brain organization/connectivity.

RESULTS

Trial enrollment will begin in early 2024.

CONCLUSIONS

After its completion in 2028, the EARHLI trial should offer evidence on the effect of hearing treatment versus a health education control on cognitive performance, social engagement, and brain organization/connectivity in 55- to 75-year-old community-dwelling adults with early ARHL and amnestic mild cognitive impairment.

Early Detection of Hearing Loss among the Elderly

BACKGROUND

Age-related hearing loss (ARHL) is a complex communication disorder that affects the cochlea and central auditory pathway. The goal of this study is to characterize this type of hearing loss and to identify non-invasive, inexpensive, and quick tests to detect ARHL among elderly adults, seeking to preserve quality of life and reduce the burden on healthcare systems.

METHODS

An observational, prospective study is conducted with >55-year-old subjects divided into the following groups: normal range (Group A), detected but not treated (Group B), and detected and treated (Group C). During follow-up, Speech Spatial Qualities (SSQ12), and Hearing Handicap Inventory in the Elderly Screening test (HHIE-S) questionnaires were assessed, along with hearing levels (hearing thresholds at 4 kHz were studied in more depth), and a series of tests and questionnaires to assess balance, cognitive level, level of dependence, and depression.

RESULTS

A total of 710 patients were included in this study. The duration of hearing loss (11.8 yr. in Group B and 21.0 yr. in Group C) and average time-to-treatment for Group C (14.1 yr.) are both protracted. Both of the used questionnaires show statistically significant differences among the groups, revealing greater handicaps for Group C. Audiometry performed at 4 kHz shows how hearing loss progresses with age, finding differences between men and women. There is a correlation between time-to-treatment in Group C and the cognitive test DSST (-0.26; p = 0.003).

CONCLUSIONS

HHIE-S, SSQ12, and 4 kHz audiometry are sensitive and feasible tests to implement in screening programs.

An Interprofessional Approach to Aural Rehabilitation for Adults with Hearing Loss and Cognitive Concerns

Individuals with hearing loss are at risk for cognitive decline. The traditional approach to audiological care does not typically involve a team approach that addresses cognitive concerns. While cognitive screening is within the scope of practice in audiology, audiologists are not typically trained in interpreting screening results or providing rehabilitation that supports cognitive health. However, as growing evidence shows that hearing loss is tied to cognitive decline, a team approach is required to support whole-person care. Speech-language pathologists, who specialize in optimizing communication, are best situated to collaborate with audiologists to provide holistic aural rehabilitation. Audiologists and speech-language pathologists who partner to support a client's communication skills and social relationships play an important role in the life of an individual with hearing loss. In this perspective, we describe relevant background information about hearing loss and cognition and present an interprofessional approach to aural rehabilitation for adults with hearing loss who have cognitive concerns. We also discuss implications for future research.

Motor Processing in Children With Cochlear Implants as Assessed by Functional Near-Infrared Spectroscopy

Auditory-motor and visual-motor networks are often coupled in daily activities, such as when listening to music and dancing; but these networks are known to be highly malleable as a function of sensory input. Thus, congenital deafness may modify neural activities within the connections between the motor, auditory, and visual cortices. Here, we investigated whether the cortical responses of children with cochlear implants (CI) to a simple and repetitive motor task would differ from that of children with typical hearing (TH) and we sought to understand whether this response related to their language development. Participants were 75 school-aged children, including 50 with CI (with varying language abilities) and 25 controls with TH. We used functional near-infrared spectroscopy (fNIRS) to record cortical responses over the whole brain, as children squeezed the back triggers of a joystick that vibrated or not with the squeeze. Motor cortex activity was reflected by an increase in oxygenated hemoglobin concentration (HbO) and a decrease in deoxygenated hemoglobin concentration (HbR) in all children, irrespective of their hearing status. Unexpectedly, the visual cortex (supposedly an irrelevant region) was deactivated in this task, particularly for children with CI who had good language skills when compared to those with CI who had language delays. Presence or absence of vibrotactile feedback made no difference in cortical activation. These findings support the potential of fNIRS to examine cognitive functions related to language in children with CI.

Electroencephalogram-based objective assessment of cognitive function level associated with age-related hearing loss

Age-Related Hearing Loss (ARHL) is a common problem in aging. Numerous longitudinal cohort studies have revealed that ARHL is closely related to cognitive function, leading to a significant risk of cognitive decline and dementia. This risk gradually increases with the severity of hearing loss. We designed dual auditory Oddball and cognitive task paradigms for the ARHL subjects, then obtained the Montreal Cognitive Assessment (MoCA) scale evaluation results for all the subjects. Multi-dimensional EEG characteristics helped explore potential biomarkers to evaluate the cognitive level of the ARHL group, having a significantly lower P300 peak amplitude coupled with a prolonged latency. Moreover, visual memory, auditory memory, and logical calculation were investigated during the cognitive task paradigm. In the ARHL groups, the alpha-to-beta rhythm energy ratio in the visual and auditory memory retention period and the wavelet packet entropy value within the logical calculation period were significantly reduced. Correlation analysis between the above specificity indicators and the subjective scale results of the ARHL group revealed that the auditory P300 component characteristics could assess attention resources and information processing speed. The alpha and beta rhythm energy ratio and wavelet packet entropy can become potential indicators to determine working memory and logical cognitive computation-related cognitive ability.

The Development of Multisensory Integration at the Neuronal Level

Multisensory integration is a fundamental function of the brain. In the typical adult, multisensory neurons' response to paired multisensory (e.g., audiovisual) cues is significantly more robust than the corresponding best unisensory response in many brain regions. Synthesizing sensory signals from multiple modalities can speed up sensory processing and improve the salience of outside events or objects. Despite its significance, multisensory integration is testified to be not a neonatal feature of the brain. Neurons' ability to effectively combine multisensory information does not occur rapidly but develops gradually during early postnatal life (for cats, 4-12 weeks required). Multisensory experience is critical for this developing process. If animals were restricted from sensing normal visual scenes or sounds (deprived of the relevant multisensory experience), the development of the corresponding integrative ability could be blocked until the appropriate multisensory experience is obtained. This section summarizes the extant literature on the development of multisensory integration (mainly using cat superior colliculus as a model), sensory-deprivation-induced cross-modal plasticity, and how sensory experience (sensory exposure and perceptual learning) leads to the plastic change and modification of neural circuits in cortical and subcortical areas.

Temporal Ordering and Auditory Resolution in Individuals with Sensorineural Hearing Loss

Introduction  Peripheral hearing loss, besides causing inadequate auditory input, can lead to distortions in the tonotopic auditory map and reorganization of neural networks. Therefore, the processing of temporal aspects of a sound stimulus and, consequently, the effectiveness of human communication can be negatively impacted. Objective  To test the temporal ordering and auditory resolution of people with mild and moderate sensorineural hearing loss and to compare them with the those of people with normal hearing. Methods  A total of 19 right-handed individuals aged 16 to 59 years with mild to moderate postlingually acquired symmetric bilateral sensorineural hearing loss participated in the study. They were submitted to frequency and duration pattern tests and a random gap detection test. Results  The mean correct response rate in the frequency pattern test was of 66.3%, and, in the duration pattern test, 71.7%. The mean threshold in the random gap detection test was of 14.1 ms. A comparison with the criteria established for normal subjects without peripheral hearing loss revealed that more than half the subjects had abnormal results in the temporal ordering test, while a smaller fraction had reduced temporal resolution. Conclusions  The performance of the subjects with acquired sensorineural hearing loss was poorer than that of the participants without peripheral hearing loss. Their results on the temporal ordering test were also poorer than in the temporal resolution test, demonstrating the importance of analyzing both these auditory skills in people with peripheral hearing loss.

Compensation in neuro-system related to age-related hearing loss

BACKGROUND

Age-related hearing loss (ARHL) is a major cause of chronic disability among the elderly. Individuals with ARHL not only have trouble hearing sounds, but also with speech perception. As the perception of auditory information is reliant on integration between widespread brain networks to interpret auditory stimuli, both auditory and extra-auditory systems which mainly include visual, motor and attention systems, play an important role in compensating for ARHL.

OBJECTIVES

To better understand the compensatory mechanism of ARHL and inspire better interventions that may alleviate ARHL.

METHODS

We mainly focus on the existing information on ARHL-related central compensation. The compensatory effects of hearing aids (HAs) and cochlear implants (CIs) on ARHL were also discussed.

RESULTS

Studies have shown that ARHL can induce cochlear hair cell damage or loss and cochlear synaptopathy, which could induce central compensation including compensation of auditory and extra-auditory neural networks. The use of HAs and CIs can improve bottom-up processing by enabling 'better' input to the auditory pathways and then to the cortex by enhancing the diminished auditory signal.

CONCLUSIONS

The central compensation of ARHL and its possible correlation with HAs and CIs are current hotspots in the field and should be given focus in future research.

Age-related hearing loss associated with differences in the neural correlates of feature binding in visual working memory

The underlying neural mechanisms underpinning the association between age-related hearing loss (ARHL) and dementia remain unclear. A limitation has been the lack of functional neuroimaging studies in ARHL cohorts to help clarify this relationship. In the present study, we investigated the neural correlates of feature binding in visual working memory with ARHL (controls = 14, mild HL = 21, and moderate or greater HL = 23). Participants completed a visual change detection task assessing feature binding while their neural activity was synchronously recorded via high-density electroencephalography. There was no difference in accuracy scores for ARHL groups compared to controls. There was increased electrophysiological activity in those with ARHL, particularly in components indexing the earlier stages of visual cognitive processing. This activity was more pronounced with more severe ARHL and was associated with maintained feature binding. Source space (sLORETA) analyses indicated greater activity in networks modulated by frontoparietal and temporal regions. Our results demonstrate there may be increased involvement of neurocognitive control networks to maintain lower-order neurocognitive processing disrupted by ARHL.

[Intervention effects of bone conduction hearing aids in patients with single-sided deafness and asymmetric hearing loss]

The incidence of single-sided deafness（SSD） is increasing year by year. Due to the hearing defects of one ear, the ability of sound localization, speech recognition in noise, and quality of life of patients with single-sided deafness will be affected to varying degrees. This article reviews the intervention effects of different types of bone conduction hearing aids in patients with single-sided deafness and asymmetric hearing loss, and the differences of intervention effects between bone conduction hearing aids, contralateral routing of signal（CROS） aids, and cochlea implant（CI）, to provide a reference for the auditory intervention and clinical treatment of single-sided deafness and asymmetric hearing loss.

Potential role of Bcl2 in lipid metabolism and synaptic dysfunction of age-related hearing loss

Age-related hearing loss (ARHL) is a prevalent condition affecting millions of individuals globally. This study investigated the role of the cell survival regulator Bcl2 in ARHL through in vitro and in vivo experiments and metabolomics analysis. The results showed that the lack of Bcl2 in the auditory cortex affects lipid metabolism, resulting in reduced synaptic function and neurodegeneration. Immunohistochemical analysis demonstrated enrichment of Bcl2 in specific areas of the auditory cortex, including the secondary auditory cortex, dorsal and ventral areas, and primary somatosensory cortex. In ARHL rats, a significant decrease in Bcl2 expression was observed in these areas. RNAseq analysis showed that the downregulation of Bcl2 altered lipid metabolism pathways within the auditory pathway, which was further confirmed by metabolomics analysis. These results suggest that Bcl2 plays a crucial role in regulating lipid metabolism, synaptic function, and neurodegeneration in ARHL; thereby, it could be a potential therapeutic target. We also revealed that Bcl2 probably has a close connection with lipid peroxidation and reactive oxygen species (ROS) production occurring in cochlear hair cells and cortical neurons in ARHL. The study also identified changes in hair cells, spiral ganglion cells, and nerve fiber density as consequences of Bcl2 deficiency, which could potentially contribute to the inner ear nerve blockage and subsequent hearing loss. Therefore, targeting Bcl2 may be a promising potential therapeutic intervention for ARHL. These findings provide valuable insights into the molecular mechanisms underlying ARHL and may pave the way for novel treatment approaches for this prevalent age-related disorder.

Crossmodal plasticity in hearing loss

Crossmodal plasticity is a textbook example of the ability of the brain to reorganize based on use. We review evidence from the auditory system showing that such reorganization has significant limits, is dependent on pre-existing circuitry and top-down interactions, and that extensive reorganization is often absent. We argue that the evidence does not support the hypothesis that crossmodal reorganization is responsible for closing critical periods in deafness, and crossmodal plasticity instead represents a neuronal process that is dynamically adaptable. We evaluate the evidence for crossmodal changes in both developmental and adult-onset deafness, which start as early as mild-moderate hearing loss and show reversibility when hearing is restored. Finally, crossmodal plasticity does not appear to affect the neuronal preconditions for successful hearing restoration. Given its dynamic and versatile nature, we describe how this plasticity can be exploited for improving clinical outcomes after neurosensory restoration.

Cochlear implants: Visual evoked potentials study

Cochlear implants (CIs) are a successful alternative in cases with severe-to-profound HL. In these individuals, visual cross-modal re-organization can occur because of hearing loss where the visual cortex will recruit auditory cortical areas for visual processing.

OBJECTIVES

This work is designed to study visual evoked potentials (VEPs) in children fitted with CIs in comparison to normal hearing children.

METHOD

This work included 2 groups of children: Group I included 20 normal hearing children and study group included 25 children fitted with unilateral CIs. All cases were subjected to Thorough otological history. Check up on CIs performance using physical check and Aided sound field examination, ophthalmic examination and Pattern Visual Evoked Potentials (pVEPs).

RESULTS

Both groups showed no significant difference as regard age or sex. And both had normal ophthalmic examinations. Children of the study groups showed satisfactory aided response. As regard pVEPs, the study group showed significant higher P100 amplitude in comparison to the control group.

CONCLUSION

This study showed that deafness could induced cortical organization in the visual cortex and not limited to the auditory cortex only.

Afferent Loss, GABA, and Central Gain in Older Adults: Associations with Speech Recognition in Noise

Deficits in auditory nerve (AN) function for older adults reduce afferent input to the cortex. The extent to which the cortex in older adults adapts to this loss of afferent input and the mechanisms underlying this adaptation are not well understood. We took a neural systems approach measuring AN and cortical evoked responses within 50 older and 27 younger human adults (59 female) to estimate central gain or increased cortical activity despite reduced AN activity. Relative to younger adults, older adults' AN response amplitudes were smaller, but cortical responses were not. We used the relationship between AN and cortical response amplitudes in younger adults to predict cortical response amplitudes for older adults from their AN responses. Central gain in older adults was thus defined as the difference between their observed cortical responses and those predicted from the parameter estimates of younger adults. In older adults, decreased afferent input contributed to lower cortical GABA levels, greater central gain, and poorer speech recognition in noise (SIN). These effects on SIN occur in addition to, and independent from, effects attributed to elevated hearing thresholds. Our results are consistent with animal models of central gain and suggest that reduced AN afferent input in some older adults may result in changes in cortical encoding and inhibitory neurotransmission, which contribute to reduced SIN. An advancement in our understanding of the changes that occur throughout the auditory system in response to the gradual loss of input with increasing age may provide potential therapeutic targets for intervention.SIGNIFICANCE STATEMENT Age-related hearing loss is one of the most common chronic conditions of aging, yet little is known about how the cortex adapts to this loss of sensory input. We measured AN and cortical responses to the same stimulus in younger and older adults. In older adults we found hyperexcitability in cortical activity relative to concomitant declines in afferent input that are consistent with central gain. Lower levels of cortical GABA, an inhibitory neurotransmitter, were associated with greater central gain, which predicted poorer SIN. The results suggest that the cortex in older adults may adapt to attenuated sensory input by reducing inhibition to amplify the cortical response, but this amplification may lead to poorer SIN.

Understanding the Relationship Between Age-Related Hearing Loss and Alzheimer’s Disease: A Narrative Review

Evidence suggests that hearing loss (HL), even at mild levels, increases the long-term risk of cognitive decline and incident dementia. Hearing loss is one of the modifiable risk factors for dementia, with approximately 4 million of the 50 million cases of dementia worldwide possibly attributed to untreated HL. This paper describes four possible mechanisms that have been suggested for the relationship between age-related hearing loss (ARHL) and Alzheimer’s disease (AD), which is the most common form of dementia. The first mechanism suggests mitochondrial dysfunction and altered signal pathways due to aging as a possible link between ARHL and AD. The second mechanism proposes that sensory degradation in hearing impaired people could explain the relationship between ARHL and AD. The occupation of cognitive resource (third) mechanism indicates that the association between ARHL and AD is a result of increased cognitive processing that is required to compensate for the degraded sensory input. The fourth mechanism is an expansion of the third mechanism, i.e., the function and structure interaction involves both cognitive resource occupation (neural activity) and AD pathology as the link between ARHL and AD. Exploring the specific mechanisms that provide the link between ARHL and AD has the potential to lead to innovative ideas for the diagnosis, prevention, and/or treatment of AD. This paper also provides insight into the current evidence for the use of hearing treatments as a possible treatment/prevention for AD, and if auditory assessments could provide an avenue for early detection of cognitive impairment associated with AD.

Considering hearing loss as a modifiable risk factor for dementia

INTRODUCTION

Accumulating evidence links hearing loss to impaired cognitive performance and increased risk for dementia. Hearing loss can lead to deafferentation-induced atrophy of frontotemporal brain regions and dysregulation of cognitive control networks from increased listening effort. Hearing loss is also associated with reduced social engagement, loneliness, and depression, which are independently associated with poor cognitive function.

AREAS COVERED

We summarize the evidence and postulated mechanisms linking hearing loss to dementia in older adults and synthesize the available literature demonstrating beneficial effects of hearing remediation on brain structure and function.

EXPERT OPINION

: Further research is needed to evaluate whether treatment of hearing loss may reduce risk of cognitive decline and improve neural consequences of hearing loss. Studies may investigate the pathologic mechanisms linking these late-life disorders and identify individuals vulnerable to dementia, and future clinical trials may evaluate whether hearing treatment may reduce the risk for dementia.

Cross-Modal Reorganization From Both Visual and Somatosensory Modalities in Cochlear Implanted Children and Its Relationship to Speech Perception

HYPOTHESIS

We hypothesized that children with cochlear implants (CIs) who demonstrate cross-modal reorganization by vision also demonstrate cross-modal reorganization by somatosensation and that these processes are interrelated and impact speech perception.

BACKGROUND

Cross-modal reorganization, which occurs when a deprived sensory modality's cortical resources are recruited by other intact modalities, has been proposed as a source of variability underlying speech perception in deaf children with CIs. Visual and somatosensory cross-modal reorganization of auditory cortex have been documented separately in CI children, but reorganization in these modalities has not been documented within the same subjects. Our goal was to examine the relationship between cross-modal reorganization from both visual and somatosensory modalities within a single group of CI children.

METHODS

We analyzed high-density electroencephalogram responses to visual and somatosensory stimuli and current density reconstruction of brain activity sources. Speech perception in noise testing was performed. Current density reconstruction patterns were analyzed within the entire subject group and across groups of CI children exhibiting good versus poor speech perception.

RESULTS

Positive correlations between visual and somatosensory cross-modal reorganization suggested that neuroplasticity in different sensory systems may be interrelated. Furthermore, CI children with good speech perception did not show recruitment of frontal or auditory cortices during visual processing, unlike CI children with poor speech perception.

CONCLUSION

Our results reflect changes in cortical resource allocation in pediatric CI users. Cross-modal recruitment of auditory and frontal cortices by vision, and cross-modal reorganization of auditory cortex by somatosensation, may underlie variability in speech and language outcomes in CI children.

Brain Morphological Modifications in Congenital and Acquired Auditory Deprivation: A Systematic Review and Coordinate-Based Meta-Analysis

Neuroplasticity following deafness has been widely demonstrated in both humans and animals, but the anatomical substrate of these changes is not yet clear in human brain. However, it is of high importance since hearing loss is a growing problem due to aging population. Moreover, knowing these brain changes could help to understand some disappointing results with cochlear implant, and therefore could improve hearing rehabilitation. A systematic review and a coordinate-based meta-analysis were realized about the morphological brain changes highlighted by MRI in severe to profound hearing loss, congenital and acquired before or after language onset. 25 papers were included in our review, concerning more than 400 deaf subjects, most of them presenting prelingual deafness. The most consistent finding is a volumetric decrease in gray matter around bilateral auditory cortex. This change was confirmed by the coordinate-based meta-analysis which shows three converging clusters in this region. The visual areas of deaf children is also significantly impacted, with a decrease of the volume of both gray and white matters. Finally, deafness is responsible of a gray matter increase within the cerebellum, especially at the right side. These results are largely discussed and compared with those from deaf animal models and blind humans, which demonstrate for example a much more consistent gray matter decrease along their respective primary sensory pathway. In human deafness, a lot of other factors than deafness could interact on the brain plasticity. One of the most important is the use of sign language and its age of acquisition, which induce among others changes within the hand motor region and the visual cortex. But other confounding factors exist which have been too little considered in the current literature, such as the etiology of the hearing impairment, the speech-reading ability, the hearing aid use, the frequent associated vestibular dysfunction or neurocognitive impairment. Another important weakness highlighted by this review concern the lack of papers about postlingual deafness, whereas it represents most of the deaf population. Further studies are needed to better understand these issues, and finally try to improve deafness rehabilitation.

Hearing Loss and Cognition: What We Know and Where We Need to Go

Although a causal association remains to be determined, epidemiologic evidence suggests an association between hearing loss and increased risk of dementia. If we determine the association is causal, opportunity for targeted intervention for hearing loss may play a fundamental role in dementia prevention. In this discussion, we summarize current research on the association between hearing loss and dementia and review potential casual mechanisms behind the association (e.g., sensory-deprivation hypothesis, information-degradation hypothesis, common cause). We emphasize key areas of research which might best inform our investigation of this potential casual association. These selected research priorities include examination of the causal mechanism, measurement of co-existing hearing loss and cognitive impairment and determination of any bias in testing, potential for managing hearing loss for prevention of dementia and cognitive decline, or the potential to reduce dementia-related symptoms through the management of hearing loss. Addressing these research gaps and how results are then translated for clinical use may prove paramount for dementia prevention, management, and overall health of older adults.

Study of extravisual resting-state networks in pituitary adenoma patients with vision restoration

Background

Pituitary adenoma (PA) may compress the optic apparatus, resulting in impaired vision. Some patients can experience improved vision rapidly after surgery. During the early period after surgery, however, the change in neurofunction in the extravisual cortex and higher cognitive cortex has yet to be explored.

Objective

Our study focused on the changes in the extravisual resting-state networks in patients with PA after vision restoration.

Methods

We recruited 14 patients with PA who experienced visual improvement after surgery. The functional connectivity (FC) of 6 seeds [auditory cortex (A1), Broca’s area, posterior cingulate cortex (PCC) for the default mode network (DMN), right caudal anterior cingulate cortex for the salience network (SN) and left dorsolateral prefrontal cortex for the executive control network (ECN)] were evaluated. A paired t test was conducted to identify the differences between two groups of patients.

Results

Compared with their preoperative counterparts, patients with PA with improved vision exhibited decreased FC with the right A1 in the left insula lobule, right middle temporal gyrus and left postcentral gyrus and increased FC in the right paracentral lobule; decreased FC with the Broca in the left middle temporal gyrus and increased FC in the left insula lobule and right thalamus; decreased FC with the DMN in the right declive and right precuneus; increased FC in right Brodmann area 17, the left cuneus and the right posterior cingulate; decreased FC with the ECN in the right posterior cingulate, right angular and right precuneus; decreased FC with the SN in the right middle temporal gyrus, right hippocampus, and right precuneus; and increased FC in the right fusiform gyrus, the left lingual gyrus and right Brodmann area 19.

Conclusions

Vision restoration may cause a response of cross-modal plasticity and multisensory systems related to A1 and the Broca. The DMN and SN may be involved in top-down control of the subareas within the visual cortex. The precuneus may be involved in the DMN, ECN and SN simultaneously.

Resting-state EEG reveals global network deficiency in prelingually deaf children with late cochlear implantation

There are individual differences in rehabilitation after cochlear implantation that can be explained by brain plasticity. However, from the perspective of brain networks, the effect of implantation age on brain plasticity is unclear. The present study investigated electroencephalography functional networks in the resting state, including eyes-closed and eyes-open conditions, in 31 children with early cochlear implantation, 24 children with late cochlear implantation, and 29 children with normal hearing. Resting-state functional connectivity was measured with phase lag index, and we investigated the connectivity between the sensory regions for each frequency band. Network topology was examined using minimum spanning tree to obtain the network backbone characteristics. The results showed stronger connectivity between auditory and visual regions but reduced global network efficiency in children with late cochlear implantation in the theta and alpha bands. Significant correlations were observed between functional backbone characteristics and speech perception scores in children with cochlear implantation. Collectively, these results reveal an important effect of implantation age on the extent of brain plasticity from a network perspective and indicate that characteristics of the brain network can reflect the extent of rehabilitation of children with cochlear implantation.

Dual-Task Performance in Hearing-Impaired Older Adults-Study Protocol for a Cross-Sectional Mobile Brain/Body Imaging Study

Background: Hearing impairments are associated with reduced walking performance under Dual-task (DT) conditions. Little is known about the neural representation of DT performance while walking in this target group compared to healthy controls or younger adults. Therefore, utilizing the Mobile Brain/Body Imaging approach (MoBI), we aim at gaining deeper insights into the brain dynamics underlying the interaction of cognitive and motor processes during different DT conditions (visual and auditory) controlling for age and the potential performance decrements of older adults with hearing impairments.

Methods: The cross-sectional study integrates a multifactorial mixed-measure design. Between-subject factors grouping the sample will be age (younger vs. older adults) and hearing impairment (mild vs. not hearing impaired). The within-subject factors will be the task complexity (single- vs. DT) and cognitive task modality (visual vs. auditory). Stimuli of the cognitive task will vary according to the stimulus modality (visual vs. auditory), presentation side (left vs. right), and presentation-response compatibility (ipsilateral vs. contralateral). Analyses of DT costs and underlying neuronal correlates focus either on gait or cognitive performance. Based on an a priori sample size calculation 96 (48 healthy and 48 mildly hearing impaired) community-dwelling older adults (50–70 years) and 48 younger adults (20–30 years) will be recruited. Gait parameters of speed and rhythm will be captured. EEG activity will be recorded using 64 active electrodes.

Discussion: The study evaluates cognitive-motor interference (CMI) in groups of young and older adults as well as older adults with hearing impairment. The underlying processes of the interaction between motor and cognitive tasks will be identified at a behavioral and neurophysiological level comparing an auditory or a visual secondary task. We assume that performance differences are linked to different cognitive-motor processes, i.e., stimulus input, resource allocation, and movement execution. Moreover, for the different DT conditions (auditory vs. visual) we assume performance decrements within the auditory condition, especially for older, hearing-impaired adults. Findings will provide evidence of general mechanisms of CMI (ST vs. DT walking) as well as task-specific effects in dual-task performance while over ground walking.

Treatment of Age-Related Hearing Loss Alters Audiovisual Integration and Resting-State Functional Connectivity: A Randomized Controlled Pilot Trial

Untreated age-related hearing loss increases audiovisual integration and impacts resting state functional brain connectivity. Further, there is a relation between crossmodal plasticity and audiovisual integration strength in cochlear implant patients. However, it is currently unclear whether amplification of the auditory input by hearing aids influences audiovisual integration and resting state functional brain connectivity. We conducted a randomized controlled pilot study to investigate how the McGurk illusion, a common measure for audiovisual integration, and resting state functional brain connectivity of the auditory cortex are altered by six-month hearing aid use. Thirty-two older participants with slight-to-moderate, symmetric, age-related hearing loss were allocated to a treatment or waiting control group and measured one week before and six months after hearing aid fitting with functional magnetic resonance imaging. Our results showed a statistical trend for an increased McGurk illusion after six months of hearing aid use. We further demonstrated that an increase in McGurk susceptibility is related to a decreased hearing aid benefit for auditory speech intelligibility in noise. No significant interaction between group and time point was obtained in the whole-brain resting state analysis. However, a region of interest (ROI)-to-ROI analysis indicated that hearing aid use of six months was associated with a decrease in resting state functional connectivity between the auditory cortex and the fusiform gyrus and that this decrease was related to an increase of perceived McGurk illusions. Our study, therefore, suggests that even short-term hearing aid use alters audiovisual integration and functional brain connectivity between auditory and visual cortices.

[How the brain perceives the world in old age with all senses]

BACKGROUND

Aging is a multidimensional process that may lead to physical, psychological and social changes. This is predominantly due to a decline of sensory functions and their central processing.

MATERIAL AND METHODS

Selective literature search in Medline and the Cochrane Library.

RESULTS

In addition to specific disorders of the sensory organs, unspecific age-related degenerative processes are responsible for the high prevalence of sensory limitations in older people. This can lead to a significant reduction in the quality of life. Balance impairment, decreasing function of hearing, vision, smell and the somatosensory system are associated with an increased risk of falling and an increased mortality in older people. Furthermore, there is evidence for a link between hearing loss and cognitive decline. In addition to the functional ability of every sense on its own, the integration of multiple sensory perceptions plays an increasing role in age-related sensory limitations.

CONCLUSION

Sensory impairments have to be considered when working with older people. Early detection and an interdisciplinary therapeutic approach can reduce the negative consequences. Multimodal stimulation appears to stimulate brain plasticity which helps to compensate age-related changes.

Neural links between facial emotion recognition and cognitive impairment in presbycusis

OBJECTIVES

Facial emotion recognition (FER) is impaired in people with dementia and with severe to profound hearing loss, probably reflecting common neural changes. Here, we aim to study the association between brain structures and FER impairment in mild to moderate age-related hearing loss participants.

METHODS

We evaluated FER in a cross-sectional cohort of 111 Chilean nondemented elderly participants. They were assessed for FER in seven different categories using 35 facial stimuli. We collected pure-tone average (PTA) audiometric thresholds, cognitive and neuropsychiatric assessments, and morphometric brain imaging using a 3-Tesla MRI.

RESULTS

According to PTA threshold levels, participants were classified as controls (≤25 dB, n = 56) or presbycusis (>25 dB, n = 55), with an average PTA of 17.08 ± 4.8 dB HL and 36.27 ± 9.5 dB HL respectively. Poorer total FER score was correlated with worse hearing thresholds (r = -0.23, p < 0.05) in participants with presbycusis. Multiple regression models explained 57 % of the variability of FER in presbycusis and 10% in controls. In both groups, the main determinant of FER was cognitive performance. In the brain structure of presbycusis participants, FER was correlated with the atrophy of the right insula, right hippocampus, bilateral cingulate cortex and multiple areas of the temporal cortex. In controls, FER was only associated with bilateral middle temporal cortex volume.

CONCLUSIONS

FER impairment in presbycusis is distinctively associated with atrophy of neural structures engaged in the perceptual and conceptual level of face emotion processing.

Screening Tools and Assessment Methods of Cognitive Decline Associated With Age-Related Hearing Loss: A Review

Strong links between hearing and cognitive function have been confirmed by a growing number of cross-sectional and longitudinal studies. Seniors with age-related hearing loss (ARHL) have a significantly higher cognitive impairment incidence than those with normal hearing. The correlation mechanism between ARHL and cognitive decline is not fully elucidated to date. However, auditory intervention for patients with ARHL may reduce the risk of cognitive decline, as early cognitive screening may improve related treatment strategies. Currently, clinical audiology examinations rarely include cognitive screening tests, partly due to the lack of objective quantitative indicators with high sensitivity and specificity. Questionnaires are currently widely used as a cognitive screening tool, but the subject's performance may be negatively affected by hearing loss. Numerous electroencephalogram (EEG) and magnetic resonance imaging (MRI) studies analyzed brain structure and function changes in patients with ARHL. These objective electrophysiological tools can be employed to reveal the association mechanism between auditory and cognitive functions, which may also find biological markers to be more extensively applied in assessing the progression towards cognitive decline and observing the effects of rehabilitation training for patients with ARHL. In this study, we reviewed clinical manifestations, pathological changes, and causes of ARHL and discussed their cognitive function effects. Specifically, we focused on current cognitive screening tools and assessment methods and analyzed their limitations and potential integration.

Neural correlates of visual stimulus encoding and verbal working memory differ between cochlear implant users and normal-hearing controls

A common concern for individuals with severe‐to‐profound hearing loss fitted with cochlear implants (CIs) is difficulty following conversations in noisy environments. Recent work has suggested that these difficulties are related to individual differences in brain function, including verbal working memory and the degree of cross‐modal reorganization of auditory areas for visual processing. However, the neural basis for these relationships is not fully understood. Here, we investigated neural correlates of visual verbal working memory and sensory plasticity in 14 CI users and age‐matched normal‐hearing (NH) controls. While we recorded the high‐density electroencephalogram (EEG), participants completed a modified Sternberg visual working memory task where sets of letters and numbers were presented visually and then recalled at a later time. Results suggested that CI users had comparable behavioural working memory performance compared with NH. However, CI users had more pronounced neural activity during visual stimulus encoding, including stronger visual‐evoked activity in auditory and visual cortices, larger modulations of neural oscillations and increased frontotemporal connectivity. In contrast, during memory retention of the characters, CI users had descriptively weaker neural oscillations and significantly lower frontotemporal connectivity. We interpret the differences in neural correlates of visual stimulus processing in CI users through the lens of cross‐modal and intramodal plasticity.

[The efficacy of modified mini-mental state examination in patients with severe to profound hearing loss]

Objective:To evaluate the efficacy of modified mini-mental state examination（MMSE） in elderly patients with severe to profound hearing loss. Methods:A total of 24 elderly patients with severe to profound hearing loss from April to June 2019 were involved. Severe to profound hearing loss was defined by a pure-tone average of hearing thresholds at 0.5, 1, 2, and 4 kHz in the better-hearing ear. Modified and original MMSE was completed for the patients at first visit. Two weeks later, they all return hospital and MMSE were carried out by the other method. The aggregate score and subitem score of MMSE by modified and original instrument were analyzed. The degree of cognitive impairment evaluated by two methods were compared. Results:Among the 24 patients, the mean MMSE score by routine method and improved method were 10.88±9.70 and 25.29±3.70（P<0.01）. The average score of sub-items of MMSE with routine method and improved method are as follows: orientation 3.21±4.03 vs 8.71±1.92（P<0.01）, registration 1.04±1.33 vs 2.79±0.51（P<0.01）, attention and calculation 1.63±2.02 vs 4.00±1.41（P<0.01）, recall 0.79±1.14 vs 2.50±0.72（P<0.01）, language 4.21±2.11 vs 7.29±1.33（P<0.01）. Compared with the routine method, the degree of cognitive impairment getting better in 83.3% patients with improved method, meanwhile, 16.7% of the patients remain the same and no deterioration. Conclusion:The routine method of MMSE should be improved to seek the real cognitive state of the patients with severe to profound hearing loss.

Hearing Impairment and Cognition in an Aging World

With the increasing number of older adults around the world, the overall number of dementia cases is expected to rise dramatically in the next 40 years. In 2020, nearly 6 million individuals in the USA were living with Alzheimer's disease, the most common type of dementia, with anticipated growth to nearly 14 million by year 2050. This increasing prevalence, coupled with high societal burden, makes prevention and intervention of dementia a medical and public health priority. As clinicians and researchers, we will continue to see more individuals with hearing loss with other comorbidities including dementia. Epidemiologic evidence suggests an association between hearing loss and increased risk of dementia, presenting opportunity for targeted intervention for hearing loss to play a fundamental role in dementia prevention. In this discussion, we summarize current research on the association between hearing loss and dementia and review potential casual mechanisms behind the association (e.g., sensory-deprivation hypothesis, information-degradation hypothesis, common cause). We emphasize key areas of research which might best inform our investigation of this potential casual association. These selected research priorities include examination of the causal mechanism, measurement of co-existing hearing loss and cognitive impairment, and potential of aural rehabilitation. Addressing these research gaps and how results are then translated for clinical use is paramount for dementia prevention and overall health of older adults.

Changes of the Brain Causal Connectivity Networks in Patients With Long-Term Bilateral Hearing Loss

It remains poorly understood how brain causal connectivity networks change following hearing loss and their effects on cognition. In the current study, we investigated this issue. Twelve patients with long-term bilateral sensorineural hearing loss [mean age, 55.7 ± 2.0; range, 39–63 years; threshold of hearing level (HL): left ear, 49.0 ± 4.1 dB HL, range, 31.25–76.25 dB HL; right ear, 55.1 ± 7.1 dB HL, range, 35–115 dB HL; the duration of hearing loss, 16.67 ± 4.5, range, 3–55 years] and 12 matched normally hearing controls (mean age, 52.3 ± 1.8; range, 42–63 years; threshold of hearing level: left ear, 17.6 ± 1.3 dB HL, range, 11.25–26.25 dB HL; right ear, 19.7 ± 1.3 dB HL, range, 8.75–26.25 dB HL) participated in this experiment. We constructed and analyzed the causal connectivity networks based on functional magnetic resonance imaging data of these participants. Two-sample t-tests revealed significant changes of causal connections and nodal degrees in the right secondary visual cortex, associative visual cortex, right dorsolateral prefrontal cortex, left subgenual cortex, and the left cingulate cortex, as well as the shortest causal connectivity paths from the right secondary visual cortex to Broca’s area in hearing loss patients. Neuropsychological tests indicated that hearing loss patients presented significant cognitive decline. Pearson’s correlation analysis indicated that changes of nodal degrees and the shortest causal connectivity paths were significantly related with poor cognitive performances. We also found a cross-modal reorganization between associative visual cortex and auditory cortex in patients with hearing loss. Additionally, we noted that visual and auditory signals had different effects on neural activities of Broca’s area, respectively. These results suggest that changes in brain causal connectivity network are an important neuroimaging mark of cognitive decline. Our findings provide some implications for rehabilitation of hearing loss patients.

Neural circuits and behavioral pathways linking hearing loss to affective dysregulation in older adults

Substantial evidence now links age-related hearing loss to incident major depressive disorder in older adults. However, research examining the neural circuits and behavioral mechanisms by which age-related hearing loss leads to depression is at an early phase. It is known that hearing loss has adverse structural and functional brain consequences, is associated with reduced social engagement and loneliness, and often results in tinnitus, which can independently affect cognitive control and emotion processing circuits. While pathways leading from these sequelae of hearing loss to affective dysregulation and depression are intuitive to hypothesize, few studies have yet been designed to provide conclusive evidence for specific pathophysiological mechanisms. Here we review the neurobiological and behavioral consequences of age-related hearing loss, present a model linking them to increased risk for major depressive disorder and suggest how future studies may facilitate the development of rationally designed therapeutic interventions for older adults with impaired hearing to reduce risk for depression and/or ameliorate depressive symptoms.

Social factors may mediate the relationship between subjective age-related hearing loss and episodic memory

Objectives: To investigate whether the relationship between subjective age-related hearing loss (SARHL) and episodic memory functioning is mediated by measures of social functioning.Methods: Using data from 8,163 adults over 50 that participated in the Irish Longitudinal Study of Ageing (three waves, each two years apart), we used a multiple mediation model within a Structural Equation Modelling framework to explore potential social mediators of the relationship between SARHL and episodic memory functioning, controlling for demographic and health covariates.Results: Neither the direct effect of self-reported hearing difficulties on memory functioning (β = -.03), nor the total effect (β = .01), were significant. A small inconsistent indirect effect of self-reported hearing difficulties on episodic memory via weekly social activity engagement (β = -.002) was found.Conclusions: Self-reported hearing difficulties may exert an indirect effect on episodic memory via weekly social activity engagement. The findings may have implications for identification of individuals at risk of memory decline in later life.

When Hearing Does Not Mean Understanding: On the Neural Processing of Syntactically Complex Sentences by Listeners With Hearing Loss

Purpose Adults with mild-to-moderate age-related hearing loss typically exhibit issues with speech understanding, but their processing of syntactically complex sentences is not well understood. We test the hypothesis that listeners with hearing loss' difficulties with comprehension and processing of syntactically complex sentences are due to the processing of degraded input interfering with the successful processing of complex sentences. Method We performed a neuroimaging study with a sentence comprehension task, varying sentence complexity (through subject-object order and verb-arguments order) and cognitive demands (presence or absence of a secondary task) within subjects. Groups of older subjects with hearing loss (n = 20) and age-matched normal-hearing controls (n = 20) were tested. Results The comprehension data show effects of syntactic complexity and hearing ability, with normal-hearing controls outperforming listeners with hearing loss, seemingly more so on syntactically complex sentences. The secondary task did not influence off-line comprehension. The imaging data show effects of group, sentence complexity, and task, with listeners with hearing loss showing decreased activation in typical speech processing areas, such as the inferior frontal gyrus and superior temporal gyrus. No interactions between group, sentence complexity, and task were found in the neuroimaging data. Conclusions The results suggest that listeners with hearing loss process speech differently from their normal-hearing peers, possibly due to the increased demands of processing degraded auditory input. Increased cognitive demands by means of a secondary visual shape processing task influence neural sentence processing, but no evidence was found that it does so in a different way for listeners with hearing loss and normal-hearing listeners.

Reduced resting state functional connectivity with increasing age-related hearing loss and McGurk susceptibility

Age-related hearing loss has been related to a compensatory increase in audio-visual integration and neural reorganization including alterations in functional resting state connectivity. How these two changes are linked in elderly listeners is unclear. The current study explored modulatory effects of hearing thresholds and audio-visual integration on resting state functional connectivity. We analysed a large set of resting state data of 65 elderly participants with a widely varying degree of untreated hearing loss. Audio-visual integration, as gauged with the McGurk effect, increased with progressing hearing thresholds. On the neural level, McGurk illusions were negatively related to functional coupling between motor and auditory regions. Similarly, connectivity of the dorsal attention network to sensorimotor and primary motor cortices was reduced with increasing hearing loss. The same effect was obtained for connectivity between the salience network and visual cortex. Our findings suggest that with progressing untreated age-related hearing loss, functional coupling at rest declines, affecting connectivity of brain networks and areas associated with attentional, visual, sensorimotor and motor processes. Especially connectivity reductions between auditory and motor areas were related to stronger audio-visual integration found with increasing hearing loss.