Development of Force Adaptation During Childhood

Abstract

Humans learn to make reaching movements in novel dynamic environments by acquiring an internal motor model of their limb dynamics. Here, the authors investigated how 4- to 11-year-old children (N = 39) and adults (N = 7) adapted to changes in arm dynamics, and they examined whether those data support the view that the human brain acquires inverse dynamics models (IDM) during development. While external damping forces were applied, the children learned to perform goal-directed forearm flexion movements. After changes in damping, all children showed kinematic aftereffects indicative of a neural controller that still attempted to compensate the no longer existing damping force. With increasing age, the number of trials toward complete adaptation decreased. When damping was present, forearm paths were most perturbed and most variable in the youngest children but were improved in the older children. The findings indicate that the neural representations of limb dynamics are less precise in children and less stable in time than those of adults. Such controller instability might be a primary cause of the high kinematic variability observed in many motor tasks during childhood. Finally, the young children were not able to update those models at the same rate as the older children, who, in turn, adapted more slowly than adults. In conclusion, the ability to adapt to unknown forces is a developmental achievement. The present results are consistent with the view that the acquisition and modification of internal models of the limb dynamics form the basis of that adaptive process.

Motor learning in childhood reveals distinct mechanisms for memory retention and re-learning

“…The rate of motor adaptation in children differs notably from that seen in adults for both reaching (Jansen-Osmann et al 2002;Konczak et al 2003) and walking adaptation (Musselman et al 2011;Vasudevan et al 2011). Adaptation in children tends to be slower and its time course more linear compared with adults.…”

“…Compared with adults, children acquire adapted motor patterns more slowly over a single training session, but can achieve a similar magnitude of learning (Jansen-Osmann et al 2002;Konczak et al 2003;Musselman et al 2011;Vasudevan et al 2011;Patrick et al 2014). This difference likely reflects the immaturity of the nervous system, especially the cerebellum (Morton and Bastian 2006;Vasudevan et al 2011), which continues to develop for at least the first decade of life (Caviness et al 1996;Saksena et al 2008;Tiemeier et al 2010).…”

Short-term plasticity in children's speech motor systems

“…In addition, the present results confirm earlier reports of age-related differences between school aged children's and adults' speech motor performance (Goffman & Smith, 1999;Green et al, 2000Green et al, , 2002Sharkey & Folkins, 1985;Smith & Goffman, 1998;Smith & McLean-Muse, 1986;Smith & Zelaznik, 2004;Walsh & Smith, 2002). We can view these results within the context of the two hypothetical sources of variability in children's motor performance from the limb motor control literature, neuromotor noise (Fitts, 1954;Schmidt et al, 1979;Smits-Engelsman & Van Galen, 1997;Yan et al, 2000) and short-term changes related to practice (Deutsch & Newell, 2002, 2004Engelhorn, 1988;FerrelChapus et al, 2002;Konczak et al, 2003;Lazarus et al, 1995;Manoel & Connolly, 1995;Takahashi et al, 2003;Thomas et al, 2000).…”

“…Less refined timing, greater variability, and decreased accuracy of children's movements are also characteristic of limb motor behaviors, including simultaneous clapping and stepping (Getchall & Whitall, 2003), goal-directed reaching (Konczak, Jansen-Osmann, & Kalveram, 2003;Takahashi, Nemet, Rose-Gottron, Larson, & Cooper, 2003;, bimanual circle-drawing tasks (Robertson, 2001), repetitive finger tapping (Greene & Williams, 1993;Inui & Katsura, 2002), and pointing (Bourgeois & Hay, 2003). In the developmental limb motor control literature, investigators have proposed that different sources contribute to the variability in children's performance.…”

“…They argued that practice and the utilization of feedback allow children to reduce variability and adapt to task requirements. Although children may be more variable initially than adults on motor tasks, they are able to adapt their motor performance and become more accurate and faster within a short period of time (i.e., within an experimental session) on goal directed arm and hand movements (Engelhorn, 1988;Manoel & Connolly, 1995;, on an isometric force tracking task (Lazarus, Whitall, & Franks, 1995), when required to adapt to an externally applied limb perturbation (Konczak et al, 2003;Takahashi et al, 2003), and to visual perturbation during a drawing task (Ferrel-Chapus, Hay, Olivier, Bard, & Fleury, 2002). These changes in movement proficiency that occur in the short-term cannot be accounted for by decrements in system noise due to physiological constraints, as these would be expected to change gradually over the course of development (Takahashi et al, 2003).…”