Viewpoint on the Benefit of Hearing Care on Cognitive Health.

PURPOSE: The purpose of this article is to provide a viewpoint on the recently published results showing the positive effect hearing intervention can have on mitigating the risk of cognitive decline in elderly individuals with hearing impairment. We intend to trigger a broader discussion on the implications of these results from an implementation science perspective. METHODS: Recently published results were reviewed and contextualized. RESULTS: In our view, these recent findings provide a great opportunity for hearing care professionals to change the perspective on hearing care being an essential service that contributes not only to managing challenges with audibility but to enabling healthy living and aging. CONCLUSION: As exciting as these findings are, from our perspective, they are also a call to action for the audiology field in terms of clinical implementation science. The findings guide us toward a more interprofessional approach in order to develop and test new, more holistic models of hearing care.

Guidelines for Best Practice in the Audiological Management of Adults with Severe and Profound Hearing Loss.

Individuals with severe to profound hearing loss are likely to present with complex listening needs that require evidence-based solutions. This document is intended to inform the practice of hearing care professionals who are involved in the audiological management of adults with a severe to profound degree of hearing loss and will highlight the special considerations and practices required to optimize outcomes for these individuals.

Auditory Training Supports Auditory Rehabilitation: A State-of-the-Art Review.

OBJECTIVES: Auditory training (AT), which is active listening to various auditory stimuli, aims to improve auditory skills. There is evidence that AT can be used as a tool in auditory rehabilitation to improve speech perception and other auditory cognitive skills in individuals with hearing impairment. The present state-of-the-art review examines the effect of AT on communication abilities in individuals with hearing impairment. In particular, transfer of AT effects on performance in untrained speech perception tasks was evaluated. DESIGN: PubMed, Medline, and Web of Science databases were searched using combinations of key words with restriction to the publication date from December 2012 until December 2018. The participant, intervention, control, outcome, and study design criteria were used for the inclusion of articles. Only studies comparing effects in an intervention group to a control group were considered. The target group included individuals with a mild to moderately severe hearing impairment, with and without hearing-aid experience. Out of 265 article abstracts reviewed, 16 met the predefined criteria and were taken for review. RESULTS: The majority of studies that were included in this state of- the-art review report at least one outcome measure that shows an improvement in non-trained tasks after a period of intense AT. However, observed shortcomings are that a comparison between studies remains difficult as training benefits were assessed with various outcome measures. Also, the sustainability of training benefits was not investigated sufficiently. CONCLUSIONS: Recent evidence suggests that intensive auditory (-cognitive) training protocols are a valid tool to improve auditory communication skills. Individuals with hearing impairment seem to benefit the most using a combination of sensory rehabilitation with hearing aids and AT to enhance auditory rehabilitation. Long term benefits of AT are still not consistently observed and should be in the focus of future research.

Hearing-impaired listeners show increased audiovisual benefit when listening to speech in noise.

Recent studies provide evidence for changes in audiovisual perception as well as for adaptive cross-modal auditory cortex plasticity in older individuals with high-frequency hearing impairments (presbycusis). We here investigated whether these changes facilitate the use of visual information, leading to an increased audiovisual benefit of hearing-impaired individuals when listening to speech in noise. We used a naturalistic design in which older participants with a varying degree of high-frequency hearing loss attended to running auditory or audiovisual speech in noise and detected rare target words. Passages containing only visual speech served as a control condition. Simultaneously acquired scalp electroencephalography (EEG) data were used to study cortical speech tracking. Target word detection accuracy was significantly increased in the audiovisual as compared to the auditory listening condition. The degree of this audiovisual enhancement was positively related to individual high-frequency hearing loss and subjectively reported listening effort in challenging daily life situations, which served as a subjective marker of hearing problems. On the neural level, the early cortical tracking of the speech envelope was enhanced in the audiovisual condition. Similar to the behavioral findings, individual differences in the magnitude of the enhancement were positively associated with listening effort ratings. Our results therefore suggest that hearing-impaired older individuals make increased use of congruent visual information to compensate for the degraded auditory input.

Source-Modeling Auditory Processes of EEG Data Using EEGLAB and Brainstorm.

Electroencephalography (EEG) source localization approaches are often used to disentangle the spatial patterns mixed up in scalp EEG recordings. However, approaches differ substantially between experiments, may be strongly parameter-dependent, and results are not necessarily meaningful. In this paper we provide a pipeline for EEG source estimation, from raw EEG data pre-processing using EEGLAB functions up to source-level analysis as implemented in Brainstorm. The pipeline is tested using a data set of 10 individuals performing an auditory attention task. The analysis approach estimates sources of 64-channel EEG data without the prerequisite of individual anatomies or individually digitized sensor positions. First, we show advanced EEG pre-processing using EEGLAB, which includes artifact attenuation using independent component analysis (ICA). ICA is a linear decomposition technique that aims to reveal the underlying statistical sources of mixed signals and is further a powerful tool to attenuate stereotypical artifacts (e.g., eye movements or heartbeat). Data submitted to ICA are pre-processed to facilitate good-quality decompositions. Aiming toward an objective approach on component identification, the semi-automatic CORRMAP algorithm is applied for the identification of components representing prominent and stereotypic artifacts. Second, we present a step-wise approach to estimate active sources of auditory cortex event-related processing, on a single subject level. The presented approach assumes that no individual anatomy is available and therefore the default anatomy ICBM152, as implemented in Brainstorm, is used for all individuals. Individual noise modeling in this dataset is based on the pre-stimulus baseline period. For EEG source modeling we use the OpenMEEG algorithm as the underlying forward model based on the symmetric Boundary Element Method (BEM). We then apply the method of dynamical statistical parametric mapping (dSPM) to obtain physiologically plausible EEG source estimates. Finally, we show how to perform group level analysis in the time domain on anatomically defined regions of interest (auditory scout). The proposed pipeline needs to be tailored to the specific datasets and paradigms. However, the straightforward combination of EEGLAB and Brainstorm analysis tools may be of interest to others performing EEG source localization.

Comorbidities of hearing loss and the implications of multimorbidity for audiological care.

With increasing age, the risk of developing chronic health conditions also increases, and many older people suffer from multiple co-existing health conditions, i.e., multimorbidity. One common health condition at older age is hearing loss (HL). The current article reflects on the implications for audiological care, when HL is one of several health conditions in a multimorbidity. An overview of health conditions often co-existing with HL, so called comorbidities, is provided, including indications for the strength of the associations. The overview is based on a literature study examining cohort studies that were published in the years 2010-2018 and examined associations of hearing loss with other health conditions, namely Visual impairment, Mobility restrictions, Cognitive impairment, Psychosocial health problems, Diabetes, Cardiovascular diseases, Stroke, Arthritis, and Cancer. This selection was based on previous publications on common chronic health conditions at older age and comorbidities of hearing loss. For all of these health conditions, it was found that prevalence is larger in people with a HL and several longitudinal studies also found increased incident rates in people with a HL. The examined publications provide little information on how hearing loss should be managed in the clinical care of its comorbidities and vice versa. The current article discusses several options for adaptations of current care. Nonetheless, solutions for an integrated audiology care model targeting HL in a multimorbidity are still lacking and should be subject to future research.

Auditory cross-modal reorganization in cochlear implant users indicates audio-visual integration.

There is clear evidence for cross-modal cortical reorganization in the auditory system of post-lingually deafened cochlear implant (CI) users. A recent report suggests that moderate sensori-neural hearing loss is already sufficient to initiate corresponding cortical changes. To what extend these changes are deprivation-induced or related to sensory recovery is still debated. Moreover, the influence of cross-modal reorganization on CI benefit is also still unclear. While reorganization during deafness may impede speech recovery, reorganization also has beneficial influences on face recognition and lip-reading. As CI users were observed to show differences in multisensory integration, the question arises if cross-modal reorganization is related to audio-visual integration skills. The current electroencephalography study investigated cortical reorganization in experienced post-lingually deafened CI users (n = 18), untreated mild to moderately hearing impaired individuals (n = 18) and normal hearing controls (n = 17). Cross-modal activation of the auditory cortex by means of EEG source localization in response to human faces and audio-visual integration, quantified with the McGurk illusion, were measured. CI users revealed stronger cross-modal activations compared to age-matched normal hearing individuals. Furthermore, CI users showed a relationship between cross-modal activation and audio-visual integration strength. This may further support a beneficial relationship between cross-modal activation and daily-life communication skills that may not be fully captured by laboratory-based speech perception tests. Interestingly, hearing impaired individuals showed behavioral and neurophysiological results that were numerically between the other two groups, and they showed a moderate relationship between cross-modal activation and the degree of hearing loss. This further supports the notion that auditory deprivation evokes a reorganization of the auditory system even at early stages of hearing loss.

Enhanced visual adaptation in cochlear implant users revealed by concurrent EEG-fNIRS.

Previous studies have observed lower visual cortex activation for visual processing in cochlear implant (CI) users compared to normal hearing controls, while others reported enhanced visual speechreading abilities in CI users. The present work investigated whether lower visual cortical activation for visual processing can be explained by a more efficient visual sensory encoding in CI users. Specifically, we investigated whether CI users show enhanced stimulus-specific adaptation for visual stimuli compared to controls. Auditory sensory adaptation was also investigated to explore the sensory specificity of the predicted effect. Twenty post-lingually deafened adult CI users and twenty age-matched controls were presented with repeated visual and auditory stimuli during simultaneous acquisition of electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS). By integrating EEG and fNIRS signals we found significantly enhanced visual adaptation and lower visual cortex activation in CI users compared to controls. That is, responses to repeated visual stimuli decreased more prominently in CI users than in controls. The results suggest that CI users process visual stimuli more efficiently than controls.

McGurk stimuli for the investigation of multisensory integration in cochlear implant users: The Oldenburg Audio Visual Speech Stimuli (OLAVS).

The concurrent presentation of different auditory and visual syllables may result in the perception of a third syllable, reflecting an illusory fusion of visual and auditory information. This well-known McGurk effect is frequently used for the study of audio-visual integration. Recently, it was shown that the McGurk effect is strongly stimulus-dependent, which complicates comparisons across perceivers and inferences across studies. To overcome this limitation, we developed the freely available Oldenburg audio-visual speech stimuli (OLAVS), consisting of 8 different talkers and 12 different syllable combinations. The quality of the OLAVS set was evaluated with 24 normal-hearing subjects. All 96 stimuli were characterized based on their stimulus disparity, which was obtained from a probabilistic model (cf. Magnotti & Beauchamp, 2015). Moreover, the McGurk effect was studied in eight adult cochlear implant (CI) users. By applying the individual, stimulus-independent parameters of the probabilistic model, the predicted effect of stronger audio-visual integration in CI users could be confirmed, demonstrating the validity of the new stimulus material.

Cortical reorganization in postlingually deaf cochlear implant users: Intra-modal and cross-modal considerations.

With the advances of cochlear implant (CI) technology, many deaf individuals can partially regain their hearing ability. However, there is a large variation in the level of recovery. Cortical changes induced by hearing deprivation and restoration with CIs have been thought to contribute to this variation. The current review aims to identify these cortical changes in postlingually deaf CI users and discusses their maladaptive or adaptive relationship to the CI outcome. Overall, intra-modal and cross-modal reorganization patterns have been identified in postlingually deaf CI users in visual and in auditory cortex. Even though cross-modal activation in auditory cortex is considered as maladaptive for speech recovery in CI users, a similar activation relates positively to lip reading skills. Furthermore, cross-modal activation of the visual cortex seems to be adaptive for speech recognition. Currently available evidence points to an involvement of further brain areas and suggests that a focus on the reversal of visual take-over of the auditory cortex may be too limited. Future investigations should consider expanded cortical as well as multi-sensory processing and capture different hierarchical processing steps. Furthermore, prospective longitudinal designs are needed to track the dynamics of cortical plasticity that takes place before and after implantation.

Cross-modal reorganization in cochlear implant users: Auditory cortex contributes to visual face processing.

There is converging evidence that the auditory cortex takes over visual functions during a period of auditory deprivation. A residual pattern of cross-modal take-over may prevent the auditory cortex to adapt to restored sensory input as delivered by a cochlear implant (CI) and limit speech intelligibility with a CI. The aim of the present study was to investigate whether visual face processing in CI users activates auditory cortex and whether this has adaptive or maladaptive consequences. High-density electroencephalogram data were recorded from CI users (n=21) and age-matched normal hearing controls (n=21) performing a face versus house discrimination task. Lip reading and face recognition abilities were measured as well as speech intelligibility. Evaluation of event-related potential (ERP) topographies revealed significant group differences over occipito-temporal scalp regions. Distributed source analysis identified significantly higher activation in the right auditory cortex for CI users compared to NH controls, confirming visual take-over. Lip reading skills were significantly enhanced in the CI group and appeared to be particularly better after a longer duration of deafness, while face recognition was not significantly different between groups. However, auditory cortex activation in CI users was positively related to face recognition abilities. Our results confirm a cross-modal reorganization for ecologically valid visual stimuli in CI users. Furthermore, they suggest that residual takeover, which can persist even after adaptation to a CI is not necessarily maladaptive.