Age-related Difference in Kinematics and Cerebral Cortical Processes during Discrete Drawing Movements in Children and Adults

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Research has shown developmental improvements in drawing movements during childhood. These changes may be related to protracted structural development and myelination of cortical brain structures underlying motor planning and control. However, no study to our knowledge has examined the relationship between cortical development and the emergence of accurate visuomotor behavior. This thesis characterized age-related differences in kinematics and cerebral cortical processes during the performance of discrete drawing movements in children, as compared to adults. Three groups were included in the study: young girls (6- to 7-year-olds), older girls (9- to 11-year-olds), and adult females (n=15, each). Participants performed 5cm center-out drawing movements with the dominant hand (right hand), while electroencephalography (EEG) was recorded. All participants exhibited similar task-related cortical communication (coherence) and activation (relative spectral power) in several frequency bands. Activation of motor neural resources (motor cortical potentials) in the midline pre-motor and motor regions was also similar across age groups. The similarity of the brain activation patterns for these measures may contribute to the comparable behavioral performance among all groups for root mean squared error (straightness) and movement length. However, other features of the young children's brain activation patterns and motor control were different than the older children and/or adults. Specifically, the young children showed increased activation of frontal (executive process) areas, whereas the older children and adults exhibit increased relative activation in task-relevant sensorimotor areas (as measured by spectral power) in frequencies related to sensorimotor processes and attention. Similarly, increased coherence in the lower beta and gamma bands, indicative of local networking, was found in the adults between the frontal and central regions, and the frontal and parietal areas. Moreover, the adults show increased activation of the contralateral sensorimotor areas time-locked to the onset of movement, compared with the young children. The increased activation of the motor areas and visuomotor networks during movement planning may contribute to faster, smoother, and more consistent behavioral performance for the older children and adults, not evident in the young children.