Electrophysiologic Assessment of Auditory Training Benefits in Older Adults

Exploring neurocognitive factors and brain activation in adult cochlear implant recipients associated with speech perception outcomes-A scoping review

Background

Cochlear implants (CIs) are considered an effective treatment for severe-to-profound sensorineural hearing loss. However, speech perception outcomes are highly variable among adult CI recipients. Top-down neurocognitive factors have been hypothesized to contribute to this variation that is currently only partly explained by biological and audiological factors. Studies investigating this, use varying methods and observe varying outcomes, and their relevance has yet to be evaluated in a review. Gathering and structuring this evidence in this scoping review provides a clear overview of where this research line currently stands, with the aim of guiding future research.

Objective

To understand to which extent different neurocognitive factors influence speech perception in adult CI users with a postlingual onset of hearing loss, by systematically reviewing the literature.

Methods

A systematic scoping review was performed according to the PRISMA guidelines. Studies investigating the influence of one or more neurocognitive factors on speech perception post-implantation were included. Word and sentence perception in quiet and noise were included as speech perception outcome metrics and six key neurocognitive domains, as defined by the DSM-5, were covered during the literature search (Protocol in open science registries: 10.17605/OSF.IO/Z3G7W of searches in June 2020, April 2022).

Results

From 5,668 retrieved articles, 54 articles were included and grouped into three categories using different measures to relate to speech perception outcomes: (1) Nineteen studies investigating brain activation, (2) Thirty-one investigating performance on cognitive tests, and (3) Eighteen investigating linguistic skills.

Conclusion

The use of cognitive functions, recruiting the frontal cortex, the use of visual cues, recruiting the occipital cortex, and the temporal cortex still available for language processing, are beneficial for adult CI users. Cognitive assessments indicate that performance on non-verbal intelligence tasks positively correlated with speech perception outcomes. Performance on auditory or visual working memory, learning, memory and vocabulary tasks were unrelated to speech perception outcomes and performance on the Stroop task not to word perception in quiet. However, there are still many uncertainties regarding the explanation of inconsistent results between papers and more comprehensive studies are needed e.g., including different assessment times, or combining neuroimaging and behavioral measures.

Systematic review registration

https://doi.org/10.17605/OSF.IO/Z3G7W.

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.

Case Report: Cognitive Impairment without Clinical Spinal Disease May Be the First Sign of HTLV-1 Neurological Alteration

Human t-cell lymphotropic virus type 1 (HTLV-1)-associated myelopathy (HAM) is a progressive neurological disease whose diagnosis is defined by clinical manifestations and seropositivity for HTLV-1 infection. Cognitive impairment (CI) is considered to occur after spinal impairment. A 51-year-old HTLV-1-infected man classified as an asymptomatic carrier presented difficulties in listening comprehension and executive memory. He was assessed for central auditory processing (CAP), cognition (event-related auditory evoked potential [P300]), and otoneurological functions (galvanic vestibular-evoked myogenic potential [gVEMP]). Altered responses were found in CAP, P300, and gVEMP, but the neurological examination and cognitive screening were normal. After a 2-year follow-up, we disclosed a positive Babinski sign, a mild CI, worsened P300, and gVEMP latencies, and the patient reported progressive lumbar pain and difficulty running. He was, then, reclassified as HAM. The first examination, in 2016, had already shown abnormal results in P300 and gVEMP despite the HTLV-1-asymptomatic carrier status. Therefore, tests that provide subclinical measures of neurological disease progression can be useful tools for an early diagnosis and intervention in HTLV-1 patients. Electrophysiological results had worsened as well as the clinical status and the cognitive function and the progression from asymptomatic status to an HTLV-1-associated neurological disease occurred within 2 years. Thus, HTLV-1-infected individuals with complaints of CI, hearing, or otoneurological manifestations should be submitted to neuropsychological and electrophysiological tests, allowing them to be properly cared in case of HAM progression.

Reversal of Age-Related Changes in Cortical Sound-Azimuth Selectivity with Training

The compromised abilities to understand speech and localize sounds are two hallmark deficits in aged individuals. Earlier studies have shown that age-related deficits in cortical neural timing, which is clearly associated with speech perception, can be partially reversed with auditory training. However, whether training can reverse aged-related cortical changes in the domain of spatial processing has never been studied. In this study, we examined cortical spatial processing in ~21-month-old rats that were trained on a sound-azimuth discrimination task. We found that animals that experienced 1 month of training displayed sharper cortical sound-azimuth tuning when compared to the age-matched untrained controls. This training-induced remodeling in spatial tuning was paralleled by increases of cortical parvalbumin-labeled inhibitory interneurons. However, no measurable changes in cortical spatial processing were recorded in age-matched animals that were passively exposed to training sounds with no task demands. These results that demonstrate the effects of training on cortical spatial domain processing in the rodent model further support the notion that age-related changes in central neural process are, due to their plastic nature, reversible. Moreover, the results offer the encouraging possibility that behavioral training might be used to attenuate declines in auditory perception, which are commonly observed in older individuals.

Enhanced auditory evoked potentials in musicians: A review of recent findings

Auditory evoked potentials serve as an objective mode for assessment to check the functioning of the auditory system and neuroplasticity. Literature has reported enhanced electrophysiological responses in musicians, which shows neuroplasticity in musicians. Various databases including PubMed, Google, Google Scholar and Medline were searched for references related to auditory evoked potentials in musicians from 1994 till date. Different auditory evoked potentials in musicians have been summarized in the present article. The findings of various studies may support as evidences for music-induced neuroplasticity which can be used for the treatment of various clinical disorders. The search results showed enhanced auditory evoked potentials in musicians compared to non-musicians from brainstem to cortical levels. Also, the present review showed enhanced attentive and pre-attentive skills in musicians compared to non-musicians.