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: the prefrontal cortex (PFC) is predominantly involved early in learning, whereas the primary motor cortex (M1) becomes increasingly engaged 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 engage the PFC similarly to support increased control demands in early learning, children show less pronounced modulation of M1 activation and representational similarity, suggesting that M1s capacity to form stable, sequence-related representations may still be developing in middle childhood. Significance StatementAlthough motor sequence learning has been widely studied in adults, less is known about how brain activation changes as learning progresses during childhood. This question is particularly relevant because prefrontal cortex (PFC) and primary motor cortex (M1) both support motor learning, but mature at different rates, with PFC developing relatively later than M1. Here, we used functional MRI to compare children (7-10 years) and adults performing a motor sequence learning task. We found no age-related differences in PFC engagement early in learning; instead children showed less refinement of M1 activation and neural representations over the course of learning than adults. These findings provide new insight into how the brain supports motor learning throughout development.