Motor skill learning differentially modulates functional connectivity in cortical and corticospinal networks in children, adolescents, and adults

Learning a new motor skill relies on functional reorganization of the human central nervous system (CNS). Plasticity may shape the transmission and communication between cortical regions and between cortical and spinal networks involved in sensorimotor control, but little is known about the influence of age on these adaptations. In a series of experiments, we investigated whether changes in cortical and corticospinal functional connectivity following motor practice differ among individuals at different stages of development (age range 8-30 years old). One hundred and one individuals practiced a visuomotor tracking task in a single experimental session. Functional cortico-cortical and cortico-muscular connectivity were quantified before and after motor training using non-zero lagged coherence estimated from source-reconstructed electroencephalographic (EEG) and electromyographic (EMG) time series. For cortico-cortical coherence, the focus was on sources in a pre-specified cortical network consistently implicated in motor learning. For cortico-muscular coherence, analyses were restricted to the contralateral primary motor cortex. The results showed that upregulation of connectivity in cortical and corticospinal networks, and improvements in motor performance following practice were more pronounced in adults compared to children. Control experiments demonstrated that these changes were dependent on motor practice rather than extended use and on changes in motor performance rather than absolute performance levels. We propose that the reported age-related differences reflect that the mature CNS is tuned to engage in adaptive processes, leading to increased sensorimotor connectivity and improvements in skilled performance during early motor learning. Our results contribute to a better understanding of age-related differences in the network adaptations underlying successful skill learning during human development.