Functional reorganization of upper-body movements for wheelchair control

In general, survivors of neuromotor disorders and injuries need to reorganize their body movements in order to achieve goals that used to be easy and natural. Often, disabled people are offered the option to control assistive devices that will facilitate the recovery of independence and capability in their daily lives. The knowledge acquired during the last few years in the motor control field can be used to study and enhance this learning process. Furthermore, this knowledge may aid in finding methods for optimizing the use of residual voluntary muscular control in disabled users and searching for an easily learnable map between body motor space and devices control space. To investigate movement reorganization we asked healthy subjects to control a cursor performing a reaching task using shoulders and upper arm movements. These movements were mapped to a lower dimensional space by principal components analysis and were used to control the cursor. We found that all subjects were able to learn to control the cursor with ease and precision while reducing the proportion of ineffective body movement components in favor of the components that mapped directly into the control space. Moreover, with practice the movements of the controlled device - the cursor - became faster, smother, more precise and with a nearly symmetric speed profile.