Developmental changes in motor cortex activity as infants develop functional motor skills.

Despite extensive research examining overt behavioral changes of motor skills in infants, the neural basis underlying the emergence of functional motor control has yet to be determined. We used functional near-infrared spectroscopy (fNIRS) to record hemodynamic activity of the primary motor cortex (M1) from 22 infants (11 six month-olds, 11 twelve month-olds) as they reached for an object, and stepped while supported over a treadmill. Based on the developmental systems framework, we hypothesized that as infants increased goal-directed experience, neural activity shifts from a diffused to focal pattern. Results showed that for reaching, younger infants showed diffuse areas of M1 activity that became focused by 12 months. For elicited stepping, younger infants produced much less M1 activity which shifted to diffuse activity by 12 months. Thus, the data suggest that as infants gain goal-directed experience, M1 activity emerges, initially showing a diffuse area of activity, becoming refined as the behavior stabilizes. Our data begin to document the cortical activity underlying early functional skill acquisition.