The acquisition of skilled motor abilities is an important milestone of human development, with many motor and cognitive abilities emerging during early childhood. Difficulties in acquiring motor skills often first appear during preschool age and may persist throughout adulthood if not resolved within the first decade of life (Piek, Hands, & Licari, 2012; Smith, 2006) and may be co-morbid with pervasive developmental disorders of language and cognition (McCleery, Elliott, Sampanis, & Stefanidou, 2013). Surprisingly, little is known about the relationship between brain development and the acquisition of motor abilities in early childhood, even though human neuroimaging studies have demonstrated rapid changes in brain structure and function during this period (Brown & Jernigan,

In a previous MEG study of movement-related brain activity in preschool age children, we reported that pre-movement fields and sensorimotor cortex oscillations differed from those typically observed in adults, suggesting that maturation of cortical motor networks is still incomplete by late preschool age (Cheyne et al., 2014). Here we describe the same measurements in an older group of school-aged children (6 to 8 years old) and an adult control group, in addition to repeated recordings in seven children from the original study approximately two years later. Differences were observed both longitudinally within children and between age groups. Pre-movement (readiness) fields were still not present in the oldest children, however both frequency and magnitude of movement-related mu (8-12Hz) and beta (15-30Hz) oscillations demonstrated linear increases with age. In contrast, movement-evoked gamma synchronization demonstrated a step-like transition from low to high (70-90 Hz) narrow-band oscillations, and this occurred at different ages in different children.These data provide novel evidence of linear and non-linear changes in motor cortex oscillations and delayed development of the readiness field throughout early childhood. Individual children showed large differences in maturation of movement-related brain activity, possibly reflecting differing rates of motor development.