Summary: Brain responses to sound in older children with mild-to-moderate hearing loss are reduced compared with their peers who have normal hearing.
Source: University of Cambridge
Overview: Deafness in early childhood is known to cause lasting changes in how the brain processes sound. New research published in eLife shows that even mild-to-moderate sensorineural hearing loss (MMHL) in childhood can produce measurable changes in auditory brain activity. The study suggests that earlier detection and management of mild hearing loss could reduce long-term changes in neural sound processing and support better language and learning outcomes.
The auditory system—the network of brain regions that detects and interprets sound—develops throughout childhood in response to auditory experience. In cases of profound deafness, this system often reorganises and may become more responsive to visual input. Until now, much less was known about whether smaller degrees of hearing loss during development could cause similar functional changes.
Researchers led by Dr Lorna Halliday (now at the MRC Cognition and Brain Sciences Unit, University of Cambridge) used electroencephalography (EEG) to measure late auditory evoked responses and mismatch responses in children with permanent MMHL while they listened to a range of sounds. The research examined 46 children who had been diagnosed with MMHL, dividing them into younger (8–12 years) and older (12–16 years) groups to compare patterns of brain activity across age.
The team found that younger children with MMHL showed auditory responses broadly similar to those seen in children with normal hearing. In contrast, older children with the same degree of hearing loss had noticeably smaller brain responses to sound than their normally hearing peers. To validate this developmental pattern, the researchers re-evaluated a subset of the original younger group six years later. Those children, who initially displayed typical mismatch responses, showed reduced or absent responses at follow-up despite no evidence of worsening peripheral hearing. The findings point to a functional reorganisation of auditory processing over time rather than progressive deterioration of hearing sensitivity.
Dr Axelle Calcus, lead author from PSL University, Paris, commented that children’s auditory systems adapt to the sounds they experience, so even mild-to-moderate reductions in auditory input can lead to developmental changes in the brain. The pattern observed by the researchers indicates that these changes may emerge over several years, highlighting a window in which earlier detection and support might help preserve typical auditory processing.
Dr Lorna Halliday from the University of Cambridge noted that current newborn hearing screening programmes are effective at identifying moderate-to-profound loss but are less sensitive to mild hearing impairment. As a result, children with mild hearing loss may remain undetected until school age or later. Because children with hearing difficulties often face greater challenges in language acquisition and academic progress, identifying milder forms of impairment earlier could enable timely interventions—such as hearing support, classroom accommodations and speech-language therapy—that reduce the risk of altered brain development and its downstream effects on learning.
Implications for practice and policy: The study strengthens the case for improved screening and monitoring of hearing in early childhood, including attention to mild-to-moderate loss. Longitudinal EEG measures of auditory processing, alongside behavioural assessments, can reveal changes that are not apparent from peripheral hearing tests alone. Clinicians and educators may consider closer follow-up for children with even small degrees of hearing loss, since neural changes may emerge over time and affect language and academic outcomes.
Funding: This research was funded by the Economic and Social Research Council and the European Union Horizon 2020 Programme and was carried out at University College London (UCL).
Source:
University of Cambridge
Media Contacts:
Lorna Halliday – University of Cambridge
Image Source:
Image credited to Kind, Hinter-Ohr-Gerät-Anpassung.
Original Research: Closed access. Title: “Functional brain alterations following mild-to-moderate sensorineural hearing loss in children.” Authors: Axelle Calcus, Outi Tuomainen, Ana Campos, Stuart Rosen, Lorna F Halliday. Published in eLife. DOI: 10.7554/eLife.46965.
Abstract summary: Using a longitudinal design, the study examined late auditory evoked responses and mismatch responses to speech and non-speech sounds in children with MMHL. Younger children (8–12 years) initially showed typical mismatch negativities (MMNs), while older children (12–16 years) did not. Six years later, a subset of those younger children showed reduced or absent MMNs despite stable audiometric thresholds, indicating that even mild-to-moderate hearing loss during childhood can alter neural processing of sound by late childhood and adolescence.