Neuromuscular Mechanisms of MovementVariability: Implications forRehabilitation and Augmentation

[摘要] Although speed-accuracy trade-offs and planning and execution of rapid goaldirectedmovements have garnered significant research interest, far fewer studies havereported results on the lower end of the movement speed spectrum. Not only do veryinteresting observations exist that are unique to slow movements, but an explanationof these observations is highly relevant to motor function recovery and motor skilllearning, where movements are typically slow at the initiation of therapy or learning,and movement speed increases through practice, exercise or therapy.In the first part of this thesis, based on data from nine stroke patients who underwenta month-long hybrid traditional and robotic therapy protocol, a correlationanalysis shows that measures of movement quality based on minimum jerk theoryfor movement planning correlates significantly and strongly with clinical measures ofmotor impairment. In contrast, measures of movement speed lack statistical significanceand show only weak to moderate correlations with clinical measures. Theseresults constitute an important step towards establishing a much-needed bridge betweenclinical and robotic rehabilitation research communities.In the second part, the origins of movement intermittency or variability in slowmovements are explored. A study with five healthy subjects who completed a manualcircular tracking task shows that movement intermittency increases in distal directionalong the arm during multi-joint movements. This result suggests that a neuromuscularnoise option is favored against a submovement-based central planning alternative,as the source of variability in slow movements. An additional experimental study witheight healthy subjects who completed slow elbow flexion movements at a constant slowspeed target under varying resistive torque levels demonstrates that resistive torquescan significantly decrease movement speed variability. The relationship between resistivetorque levels and speed variability, however, is not monotonic. This findingmay constitute a basis for proper design of novel human skill augmentation methodsfor delicate tasks and improve motor rehabilitation and learning protocols. Finally,a neuro-musculoskeletal model of the elbow suggests that movement speed variabilityin slow movements cannot be solely attributed to variability in the mechanics ofmuscle force generation.Together, these analyses, simulations, and experiments shed light on variabilityin slow movements, and will inform the development of novel paradigms for roboticrehabilitation, motor skill learning and augmentation.

[发布机构] Rice University

[效力级别] engineering