Planning of unconstrained reach actions after unilateral sensorimotor stroke

UnrestrictedThis dissertation was designed to determine the effects of unilateral sensorimotor stroke on the ability to use initial planning and compensatory adjustments for unconstrained reach actions. Three studies were organized to answer this question. First, because of the novel nature of the immersive virtual environment (VE), the measurement validity of the experimental paradigm was investigated. Second, to validate the VE for the study of unconstrained reach actions, task performance was compared between the VE and a real-world environment (RWE) in young, non-disabled adults. The final and most important study investigated the planning and adjustments of reach actions in individuals with sensorimotor stroke when moving with the ipsilesional and contralesional arm. To glean information about the perceived confidence of the performer, the relationship between reach performance and task-specific self-efficacy was examined.; After determination of the measurement validity of the VE, six young, non-disabled adults, 12 individuals with sensorimotor stroke (six with right brain damage and six with left brain damage), and six age-matched, non-disabled older adults were recruited. Participants performed goal-directed reach actions to six virtual targets that were presented in two directions (+45° and -45° from center) and three distances (8, 16, and 24 cm) in a single data collection session. Younger, non-disabled participants reached with the right arm only but did so in two environments: the VE and an analogous RWE. Participants with mild to moderate motor impairment after stroke and the age-matched older, non-disabled adults reached separately with the right and left arms in the VE. Individuals rated their level of self-efficacy for reach accuracy and reach speed prior to each block of trials. Reach movement kinematics were used to characterize performance and to quantify the use of initial planning and compensatory adjustments in all studies and participants.; Comparison of reach movements between the immersive VE and the RWE performed by younger, non-disabled participants revealed no significant difference in the control of these actions thereby validating the VE condition for future studies. Individuals relied on a control pattern that combined both anticipatory planning and compensatory adjustments to achieve the actual movement distance. A similar pattern of control was observed for goal-directed reaches performed with the right and left arm in the older, non-disabled participants in the VE. Goal-directed reaches performed with the ipsilesional arm resembled those of the control group in the use of initial planning and compensatory adjustments. However, reach actions performed with the contralesional arm tended to rely less on an initial plan and more on feedback based compensatory adjustments compared to the matched arm in non-disabled controls. This trend was evident in both stroke groups (right brain damage, left brain damage) but only statistically significant for the right brain damage group for reach actions across midline. Additionally, individuals with right brain damage demonstrated changes in reach kinematics with both arms that suggested they were slowing down the speed of movement to improve endpoint accuracy, a finding unique to the right brain damage group. As expected, self-efficacy for reach accuracy and reach speed was lower for the contralesional arm than for the ipsilesional arm in both the right brain damage and left brain damage groups.; Overall, the use of initial planning and compensatory adjustments in the ipsilesional arm after sensorimotor stroke did not differ from non-disabled controls. The contralesional arm demonstrated a decreased utilization of initial planning that was more significant in the right brain damage group than the left brain damage group. This change in control of goal-directed reach actions was reflected by a decrease in reach self-efficacy suggesting a perceptual awareness of paretic limb movement capability. Together, the findings of this dissertation provide a foundation for future research into the mechanisms of the control of goal-directed reach actions after stroke, the impact of training and practice conditions on that control, and the role of self-efficacy on the control and learning of these actions