Identification and Retraining of Sensorimotor Deficits to Reduce Intention Tremor in Multiple Sclerosis

IDENTIFICATION AND RETRAINING OF SENSORIMOTOR DEFICITS TO REDUCE INTENTION TREMOR IN MULTIPLE SCLEROSIS Megan Heenan Marquette University, 2015 Multiple sclerosis (MS) affects approximately 1 in 1000 Americans and is a significant cause of disability in the United States. One significant contributor to disability in MS is intention tremor, which manifests as an oscillation about the endpoint of a goal-directed movement. A major challenge of treating intention tremor is that the underlying causes of tremor in MS are unknown. In this study, we describe a systemslevel computational model and an experimental technique that parameterizes subjectspecific deficits in sensory feedback control during goal-directed movements. We used this approach to characterize sensorimotor control and examine how sensory and motor processes are differentially impacted by age and MS. The specific aims of this study were to: 1) characterize age-related changes in sensorimotor control during goal-directed movements; 2) characterize deficits in sensorimotor control in individuals with multiple sclerosis; and 3) determine whether sensorimotor control deficits can be modified and intention tremor reduced using robot-assisted therapy. We show that age-related changes in movement control can be ascribed to increases in sensory noise, leading to slower and less accurate movements. In persons with MS, changes in movement control associated with intention tremor can be attributed to increases in visual response delay that are unaccounted for by predictive neuromotor control mechanisms. Finally, we show that training of goal-directed movements using carefully selected feedback delays can enable subjects to adapt to their increased visual delay, thereby reducing system instability and tremor. The results demonstrate that systems identification techniques provide an informative framework for investigating how neuromotor disease affects motor control and for developing individually targeted rehabilitation strategies to reduce motor disability.