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Sunday, October 6, 2019

Mild-to-Moderate Hearing Loss Leads to Lasting Changes in Central Auditory System Function

Hearing loss in early childhood is known to change how sounds are processed in the brain, but new research shows that even mild to moderate levels of deafness can result in these changes. (eLife. Oct. 1, 2019; Researchers at the MRC Cognition and Brain Sciences Unit at the University of Cambridge in the United Kingdom conducted a longitudinal study to examine late auditory evoked responses and mismatch responses to nonspeech and speech sounds for 46 children with mild to moderate hearing loss (MMHL). They found that younger children (8 to 12 years old) with hearing loss showed relatively typical brain responses, similar to those of children with normal hearing. The brain responses of older children (12 to 16 years old) with hearing loss, however, were smaller than those of their hearing peers. A subset of the younger children was retested six years later, and the researchers confirmed that as the children with hearing loss grew older, their brain responses changed—responses that were present when the children were younger had either disappeared or grown smaller by the time the children were older. There was no evidence that the children's hearing loss had worsened over that period, suggesting that a functional reorganization was occurring.

Axelle Calcus, PhD, the lead author of this paper, said children's brains develop in response to exposure to sounds, so it should not be too surprising that even mild-to-moderate levels of hearing loss can lead to changes in the brain. "However, this does suggest that we need to identify these problems at an earlier stage than is currently the case."