Continued maturation of auditory brainstem function during adolescence: A longitudinal approach

Abstract

Objective Considerable attention has been devoted to understanding development of the auditory system during the first few years of life, yet comparatively little is known about maturation during adolescence. Moreover, the few studies investigating auditory system maturation in late childhood have employed a cross-sectional approach. Methods To better understand auditory development in adolescence, we used a longitudinal design to measure the subcortical encoding of speech syllables in 74 adolescents at four time points from ages 14 through 17. Results We find a developmental decrease in the spectral representation of the evoking syllable, trial-by-trial response consistency, and tracking of the amplitude envelope, while timing of the evoked response appears to be stable over this age range. Conclusions These longitudinal data provide further evidence that subcortical auditory development is a protracted process that continues throughout the first two decades of life. Specifically, our data suggest that adolescence represents a transitional point between the enhanced response during childhood and the mature, though smaller, response of adults. Significance That the auditory brainstem has not fully matured by the end of adolescence suggests that auditory enrichment begun later in childhood could lead to enhancements in auditory brainstem function and alter developmental profiles.

Music training alters the course of adolescent auditory development

“…Response consistency peaks in childhood (∼8-11 y of age), declining steadily until young adulthood (24,25); we show that this adolescent decline is mitigated by in-school music lessons. What mechanisms underlie this developmental trend and, perhaps, training effect?…”

“…We investigated the effects of music training versus JROTC training on adolescent auditory development by testing auditory neural encoding and language skills in adolescents before, and 3 years after, they entered high school. Although adolescents undergoing JROTC training exhibited the typical waning of the consistency of the subcortical response to speech (24,25), music training maintained high response consistency throughout high school. An increase in the N1/P1 amplitude ratio from year 1 to year 4, known to emerge in adolescence (21)(22)(23), was observed in the music group but had not yet emerged in the JROTC group.…”

“…For example, training group accounts for 16% of the variance in the year-to-year change in N1/P1 ratio, suggesting that there are other factors at play. Socioeconomic status, sex, and maturational progress could account for some of this variance because all three of these variables have been shown to affect auditory processing (25,90,91).…”

“…The JROTC group exhibited the waning of response consistency characteristically observed between adolescence and young adulthood (24,25). The music group, however, maintained high response consistency throughout high school.…”

“…Cortically, the P1, which is a positive deflection at around 50 ms generated within lateral Heschl's gyrus (17), declines whereas the N1, a negative deflection at around 100 ms generated within primary and secondary auditory cortices (18)(19)(20), increases (21-23). Subcortically, the trial-by-trial consistency of the response declines (24,25). An open question is how experience interacts with this developmental plasticity during adolescence.…”