Infant’s Motor System Responses to Temporal Structure in Music Beats

Abstract

Beat perception reflects the brain’s ability to extract a regular pulse in auditory rhythms, an ability crucial for early language, social, and cognitive development. Studies in newborns and infants suggest an innate sensitivity to rhythmic structure, but the brain regions involved in infant beat-perception remain unknown. In adults, motor regions¬¬—including the supplementary motor area (SMA) and preSMA— are involved in beat perception. My study aimed to localize the brain regions involved in beat perception in infants. Particularly, I am interested in the motor system responses to rhythmic (Beat) and non-rhythmic stimuli (NonBeat). Using functional near-infrared spectroscopy, I measured localized changes in cortical brain activity in 53 infants aged 203.7– 456-days while they listened to Beat and NonBeat stimuli. A post-hoc median split on age was implemented, dividing participants into Younger (203.7-273.6 days) and Older (273.6-456 days) age groups. A paired t-test revealed a significantly greater motor region activation in response to Beat compared to NonBeat condition in the Younger group. In the Older group, a non-significant reduction in motor activity was observed in response to Beat stimuli compared to NonBeat stimuli, suggesting a trend towards suppression. By manipulating the stimuli loudness, the specificity of the motor system responses to beat stimuli was measured. No difference in motor system response to stimuli loudness was observed, showing the specificity of motor responses to beat processing. These results reveal notable differences in the motor system responses to rhythmic and non-rhythmic stimuli in Younger (203.7-273.6 days) and older (273.6-456 days) infants, suggesting developmental changes in motor system engagement with rhythmic stimuli across infancy.