Colloquium: Central auditory system maturation continues throughout childhood: evidence from event-related potentials

For many years it was thought that the auditory system reached maturity in the first few years of life. Although auditory detection and discrimination are not always adult-like in children, this seemed attributable to problems in dealing with task demands, rather than genuine immaturity. More recent imaging and neuropathological studies, however, suggest that brain development continues into adolescence. I will discuss two studies with typically-developing children that demonstrate that electrophysiological responses to auditory stimuli show developmental change from 7 years through to adulthood. The first study was part of Project Kids, based at the University of Western Australia, and investigated auditory event-related potentials (ERPs) elicited by tones in 105 children on two occasions two years apart. Just over half of the children were 7 years initially and 9 years at follow-up, whereas the remainder were 9 years initially and 11 years at follow-up. Significant changes were found at each age level at fronto-central sites, whereas a flat developmental function was seen for temporal sites. We suggest that this may relate to earlier maturation of primary vs. secondary auditory cortex.

The second study was conducted in Oxford and looked at two indices of brain response to sound changes, the mismatch negativity (MMN) and late discriminative negativity (LDN) in children, teenagers and adults. These components showed complementary patterns: MMN was larger in adults than children and larger for large than small sound changes, whereas LDN showed the reverse pattern. Time-frequency analysis revealed that the MMN resulted from phase-synchronisation of oscillations in the theta (4-7 Hz) range, with greater synchronisation in adults than children. These results show that neurophysiological processes underlying auditory discrimination continue to develop through childhood and adolescence.