Hearing beyond convention
Insights from diverse animal models on the impact of mild hearing loss on social and cognitive development
Mild or hidden hearing loss in children can affect learning, memory, and social behaviour, but how these changes are linked to the brain remains unclear. Joëlle Jagersma used animal models to investigate how changes in hearing during development affect behaviour and the brain.
Experimentally induced mild hearing loss impaired memory, particularly long-term memory, while short-term memory and social behaviour were often preserved or even enhanced. This suggests that early hearing loss may particularly affect processes needed for long-term memory rather than causing a general decline in learning, memory or social abilities. The behavioural changes were accompanied by only subtle brain alterations, including changes related to myelin, the insulating material surrounding nerve fibres.
A model with naturally poor hearing showed signs that the brain might adapt to reduced auditory input, with changes in brainstem activity and communication between nerve cells. Another experiment showed that altering serotonin signalling during development alone could not explain the myelin-related changes linked to hearing loss, indicating that other biological mechanisms are involved. A broader literature review of animal studies further showed that the effects of hearing loss on learning, memory and social behaviour vary considerably and that this variance cannot reliably be explained by differences in experimental design.
Together, these findings show that early hearing loss has selective rather than uniform effects on investigated behaviours and the brain, while the brain may also adapt to reduced auditory input. Understanding this variability may ultimately help develop interventions addressing the broader developmental consequences of hearing loss.