تغییرات وابسته به سن در تصویرسازی حرکتی از دوران کودکی برای بزرگسالی: کاوش نمایش داخلی سرعت-دقت مبادلات

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.

When making reaching movements to targets of different sizes healthy performers show remarkably similar movement profiles. These profiles are adapted to task constraints like required accuracy and are scaled in a manner that minimizes energy costs and endpoint variability. The very clear trade-off between speed and accuracy, also known as Fitts’ Law (Fitts, 1954), has been described in many tasks and movement contexts, is already present in young children (Caeyenberghs et al., 2009 and Smits-Engelsman et al., 2006), and evident even in patient groups with brain damage (Caeyenberghs et al., 2009 and Smits-Engelsman et al., 2007).

Using the VRFT we confirmed that making an intended but uninitiated movement preserved the same timing parameters as those observed for real movements. This relationship was shown to increase over childhood, reaching an asymptote during adolescence. We argue that MI ability and its development captures aspects of motor prediction. In computational terms, the ability to use predictive models provides an important means of error correction during and after motor performance. In real time, for example, the predictive model provides a template against which the accuracy of the (overt) movement can be compared as it unfolds. Immaturity in this control system would necessitate that action be more reliant on slow re-afferent motor signals, adding time and error to movements performed under changing conditions. The developmental changes we observed suggest that with age, children become less reliant on feedback, and more attuned to feedforward control, a process that continues into adolescence.