How brain dynamics vary in children with hearing loss

Thanks to several successful large-scale studies of children who are hard of hearing, we know a lot about the impact of hearing loss on development.

But we still have important questions about variability in outcomes in these children.

Factors such as age of intervention, amount of hearing aid use, quality of hearing aid fit, and cognitive skills explain differences between children. However, how these different factors interact, as well as the physiological basis of these processes, remains an unanswered question.

Our team at Boys Town National Research Hospital recently conducted a study^1,2 to look at whether there are differences in brain dynamics between children. We used neuroimaging to explore:

1. Whether children with hearing loss show changes in brain activity during working memory compared to hearing children, and;
   
2. Whether individual differences in hearing aid use relate to brain dynamics involved in working memory.
   

How neuroimaging works

Neuroimaging identifies when and where cognitive or language processes occur in the brain.  

Magnetoencephalography (MEG), a type of neuroimaging, can quantify the location and amount of neural activity in the cortex every millisecond. This allows us to see how brain activity changes over time. For example, during a working memory task, a person encodes information into temporary memory, and maintains that information until it needs to be retrieved.

Encoding, maintenance, retrieval are crucial to working memory, and each process uses different areas of the brain at different times. MEG imaging allows us to measure these working memory processes.  

Impact of hearing loss and hearing aid use on the brain dynamics in working memory processing

Children performed a working memory task during MEG. We then used MEG data to examine neural activity during working memory encoding and maintenance separately.

First we compared the brain activity of children who are hard of hearing and their same-age hearing peers. We found:

• Children who are hard of hearing and children with typical hearing performed the same on the working memory task, with no differences in accuracy or reaction time.

• Children who are hard of hearing had significantly increased brain activity during each phase of working memory. This suggests that the brains of children with hearing loss “work harder” during working memory tasks compared to their hearing peers.

In a laboratory setting, children with and without hearing loss may not show differences in behavior, but there may be significantly different brain mechanisms driving working memory performance.

Within the children who are hard of hearing, we found:

• Greater hearing aid use was significantly related to a more “typical” pattern of brain activity during working memory, even after controlling for degree of hearing loss.

Clinical implications

Neuroimaging may explain why we see differences in outcomes in children with hearing loss. Going forward, we hope that neuroimaging can inform individualized therapies for children who are hard of hearing.

Every brain is different, and by measuring the brain’s response to therapy, we may be able to improve outcomes in every child.

To learn more on this topic, I invite you to read recent publications in NeuroImage: Clinical  and Ear and Hearing.

---

References

1. Heinrichs-Graham, E., Walker, E.A., Eastman, J.A., Frenzel, M.R., Joe, T.R., McCreery, R.W.  (2021). The impact of mild-to-severe hearing loss on the neural dynamics serving verbal working memory processing in children. Neuroimage Clin; 30:102647.
   
2. Heinrichs-Graham, E., Walker, E.A., Eastman, J.A., Frenzel, M.R., McCreery, R.W. (2021). Amount of hearing aid use impacts neural oscillatory dynamics underlying verbal working memory processing in children with hearing loss. Ear Hear; 20.