Age-related changes in motor imagery from early childhood to adulthood: probing the internal representation of speed-accuracy trade-offs.

The purpose of this study was to chart the development of motor imagery ability between 5 and 29 years of age and its relationship to fine-motor skill. 237 participants performed a computerized Virtual Radial Fitts Task (VRFT) as a measure of Motor Imagery (MI) ability. Participants aimed at five targets, positioned along radial axes from a central target circle. The targets differed in width over trials (2.5, 5, 10, 20 or 40 mm). Performance was indexed by the relationship between the movement time (MT) in executed and imagined movements. A subset of participants (11-19 years old, n=22) also performed the task with their non-preferred hand. We also examined if manual skill (measured by peg board task and posting coins) was related to the executed and imagined MT on the VRFT. Our results showed that the accuracy of the imagined movement improved steadily over childhood, reaching an asymptote during adolescence and into early adulthood. The correlation between the real and virtual MT using the preferred hand did not differ appreciably from that using the non-preferred hand. If the children could perform the tasks with their non-preferred hand (11 years and older), they also scaled performance in relatively precise terms using the less dextrous non-preferred hand. The correlation between real MT on the VRFT and fine-motor performance ranged between .53 and .42, while that for virtual movement was between .37 and .34. MI ability predicts manual skill to a moderate degree.