Development of motor learning in children with autism
When a robotic manipulandum, such as the PHANTOM device, is programmed to create a novel, movement-contingent force field, a subject’s first attempt to transport its handle to a target is deviated from the baseline path but with practice the subject regains accuracy. Adults who adapt to a dynamic force field produced by a robotic manipulandum later show aftereffects when manipulating the deactivated robot but move accurately with their free arm, indicating that self-calibration of limb dynamics and learning of robot dynamics can be acquired and recruited separately.
We have performed a cross-sectional study of context-specific self/object motor adaptation in children 3 to 14 years old. All children adapted to an orthogonal (counterclockwise), velocity-dependent field and later showed after effects when reaching while gripping the deactivated robot. However, only subjects younger than about 7 years showed aftereffects when reaching with the free hand. This shows that the ability to separately modify control of one’s own body and of external objects in a context-specific manner is a developmental achievement.
In a second experiment with children of the same age range, the robot applied a more familiar anti-parallel (damping-like) velocity-dependent force field, which initially retarded movement trajectories. After adaptation, reaches made while grasping the inactivated manipulandum showed negative aftereffects and free reaches showed no aftereffects, independent of age. This implicates a role of experience in the development of context-specific self/object motor adaptation.
We have also used the robotic adaptation paradigm to compare context-specific, self/object motor adaptation to an orthogonal, velocity-dependent force field in children 3 to 14 years old with high-functioning autism and a new group additional typically developing children. Performance of the new typically developing group replicated the earlier study. Every child with high-functioning autism showed the pattern exhibited by typical children younger than 7, of aftereffects with both free hand reaches and of reaches made while gripping the deactivated robot. These results indicate a delay of self/object motor learning discrimination in individuals with HFA.
Ongoing experiments are studying the factors regulating the typical development of context-specific motor learning, possible means for mitigating the delay in children with autism and possible therapeutic applications of overcoming the delay.