Amount of Hearing Aid Use Impacts Neural Oscillatory Dynamics Underlying Verbal Working Memory Processing for Children With Hearing Loss

Better with age: Developmental changes in oscillatory activity during verbal working memory encoding and maintenance

Numerous investigations have characterized the oscillatory dynamics serving working memory in adults, but few have probed its relationship with chronological age in developing youth. We recorded magnetoencephalography during a modified Sternberg verbal working memory task in 82 youth participants aged 6-14 years old. Significant oscillatory responses were identified and imaged using a beamforming approach and the resulting whole-brain maps were probed for developmental effects during the encoding and maintenance phases. Our results indicated robust oscillatory responses in the theta (4-7 Hz) and alpha (8-14 Hz) range, with older participants exhibiting stronger alpha oscillations in left-hemispheric language regions. Older participants also had greater occipital theta power during encoding. Interestingly, there were sex-by-age interaction effects in cerebellar cortices during encoding and in the right superior temporal region during maintenance. These results extend the existing literature on working memory development by showing strong associations between age and oscillatory dynamics across a distributed network. To our knowledge, these findings are the first to link chronological age to alpha and theta oscillatory responses serving working memory encoding and maintenance, both across and between male and female youth; they reveal robust developmental effects in crucial brain regions serving higher order functions.

Somatosensory gating is related to behavioral and verbal outcomes in children with mild-to-severe hearing loss

Sensory gating is a process by which the brain filters out redundant information to preserve neural resources for behaviorally relevant stimuli. Although studies have shown alterations in auditory and visual processing in children who are hard-of-hearing (CHH) relative to children with normal hearing (CNH), it is unclear whether these alterations extend to the somatosensory domain, and how aberrations in sensory processing affect sensory gating. In this study, CHH and CNH were presented with a paired-pulse median nerve stimulation during magnetoencephalography. Stimulus-related gamma neural activity was imaged and virtual time series from peak somatosensory responses were extracted. We found significant effects of both stimulus and group, as well as a significant group-by-stimulus interaction. CHH showed a larger response to stimulation overall, as well as greater differences in gamma power from the first to the second stimulus. However, when looking at the ratio rather than the absolute difference in power, CHH showed comparable gating to CNH. In addition, smaller gating ratios were correlated with better classroom behavior and verbal ability in CHH, but not CNH. Taken together, these data underscore the importance of considering how CHH experience their multisensory environment when interpreting outcomes and designing interventions.

Gamma-Band Modulation in Parietal Area as the Electroencephalographic Signature for Performance in Auditory-Verbal Working Memory: An Exploratory Pilot Study in Hearing and Unilateral Cochlear Implant Children

This pilot study investigates the neurophysiological patterns of visual and auditory verbal working memory (VWM) in unilateral cochlear implant users (UCIs). We compared the task-related electroencephalogram (EEG) power spectral density of 7- to 13-year-old UCIs (n = 7) with a hearing control group (HC, n = 10) during the execution of a three-level n-back task with auditory and visual verbal (letters) stimuli. Performances improved as memory load decreased regardless of sensory modality (SM) and group factors. Theta EEG activation over the frontal area was proportionally influenced by task level; the left hemisphere (LH) showed greater activation in the gamma band, suggesting lateralization of VWM function regardless of SM. However, HCs showed stronger activation patterns in the LH than UCIs regardless of SM and in the parietal area (PA) during the most challenging audio condition. Linear regressions for gamma activation in the PA suggest the presence of a pattern-supporting auditory VWM only in HCs. Our findings seem to recognize gamma activation in the PA as the signature of effective auditory VWM. These results, although preliminary, highlight this EEG pattern as a possible cause of the variability found in VWM outcomes in deaf children, opening up new possibilities for interdisciplinary research and rehabilitation intervention.

Auditory Experience, Speech Sound Production Growth, and Early Literacy in Children Who Are Hard of Hearing

PURPOSE

Children who are hard of hearing (CHH) are at risk for literacy difficulties. Speech sound production is related to literacy skills in typically hearing children. Speech sound production abilities can also be markedly weak in CHH due to inconsistent access to the speech signal. We longitudinally examined relations between auditory experience, speech sound production abilities, and literacy (i.e., nonword reading and spelling in second grade) in CHH.

METHOD

Participants included 166 CHH. All participants used hearing aids (HAs). Auditory experience is a weighted measure of the number of hours of daily HA use and the amount of audibility with and without their HAs. Children's speech sound production was tested 2-3 times between the ages of 3 and 9 years. At age 5 years and again in second grade, children were tested on a battery of language and literacy measures.

RESULTS

Auditory experience was significantly correlated with speech sound production abilities, but age at HA fitting was not. Speech sound production abilities at age 5 years did not predict nonword reading in second grade but did predict spelling skills in second grade.

CONCLUSIONS

Our results support the importance of auditory experience and speech sound production for later literacy abilities. Specifically, we found that speech sound production abilities and print knowledge at age 5 years are related to second grade spelling outcomes. Interestingly, we found that morphological knowledge at age 5 years was more predictive of decoding in second grade than was speech sound production. Although there are multiple factors that contribute to literacy success, our results underscore the unique contributions of speech sound production abilities in CHH.

Auditory experience modulates frontoparietal theta activity serving fluid intelligence

Children who are hard of hearing are at risk for developmental language and academic delays compared with children with normal hearing. Some work suggests that high-order cognitive function, including fluid intelligence, may relate to language and academic outcomes in children with hearing loss, but findings in these studies have been mixed and to date, there have been no studies of the whole-brain neural dynamics serving fluid intelligence in the context of hearing loss. To this end, this study sought to identify the impact of hearing loss and subsequent hearing aid use on the neural dynamics serving abstract reasoning in children who are hard of hearing relative to children with normal hearing using magnetoencephalography. We found significant elevations in occipital and parietal theta activity during early stimulus evaluation in children who are hard of hearing relative to normal-hearing peers. In addition, we found that greater hearing aid use was significantly related to reduced activity throughout the fronto-parietal network. Notably, there were no differences in alpha dynamics between groups during later-stage processing nor did alpha activity correlate with hearing aid use. These cross-sectional data suggest that differences in auditory experience lead to widespread alterations in the neural dynamics serving initial stimulus processing in fluid intelligence in children.