Motor Sequence Learning in Children and Adults: Age Differences in the Time Course of Brain Activation and Representational Stability

Humans possess an astounding ability to acquire complex movement sequences with limited practice. Motor sequence learning engages a distributed network of brain regions that show distinct learning-related changes, often characterized by predominant involvement of the prefrontal cortex (PFC) early in learning and increasing engagement of the primary motor cortex (M1) later in learning. Because motor regions mature relatively earlier than the PFC during development, we examined how children and adults differ in the time course of neural changes underlying motor sequence learning. Using functional magnetic resonance imaging (fMRI), we compared brain activation in children (7--10 years, N = 39, 17 female) and adults (20--32 years, N = 39, 19 female) during an associative visuomotor learning task. In both age groups, response times decreased with sequence repetition, with greater reductions in adults than in children. Across age groups, early learning was associated with heightened PFC activation, whereas later learning was characterized by increased activation in left M1 and bilateral supplementary motor area. Children and adults showed comparable decreases in PFC activation and PFC--M1 connectivity with sequence repetition. In contrast, adults exhibited larger learning-related increases in activation and stability of multivariate patterns in left M1. Together, these findings indicate that although both age groups engaged the PFC similarly to support increased control demands in early learning, children showed less pronounced modulation of M1 activation and representational similarity, suggesting that M1's capacity to form stable, sequence-related representations may still be developing in middle childhood.