Kinesiology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2784
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Item Closed Loop System Identification of Postural Control with Bilateral Vestibular Loss(2009) Amenabar, Katharine Elizabeth; Jeka, John J; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Human upright stance can be characterized as a combination of feedback and plant. Feedback consists of integrated sensory signals, producing estimates of position and velocity of the body segments while plant includes both musculotendon dynamics and body dynamics. Separating plant and feedback is possible mathematically through closed loop system identification. By studying bilateral vestibular loss (BVL) patients it is hoped knowledge regarding human posture and the role of the vestibular system will be gained. Two BVL patients and two age, height and gender matched controls had visual and mechanical perturbations applied simultaneously to determine these properties. Both leg and trunk kinematics and EMG data were collected. Using frequency response functions plant and feedback properties were calculated. Plant and feedback dynamics differ. BVL patients show more variable weighted hip EMG data, supporting the idea that this population can not properly use hip movement with their lack of vestibular system.Item Retention of a novel visuomotor gain in patients with Parkinson's disease is context-specific(2009) Venkatakrishnan, Anusha; Contreras-Vidal, José L; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hypometria or reduced movement amplitude is a major concern in Parkinson's disease (PD) since it impairs multiple functional activities of daily living, including fine motor control tasks, such as handwriting. Recent research using virtual or computer-based environments, wherein visual information about hand movement is altered and dissociated from perception (e.g., position sense or kinesthesia) of hand movement itself, has shown increases in handwriting size in patients with PD. In fact, preliminary findings in our laboratory have shown that gradual alterations in visual feedback of movement facilitate adaptation of handwriting size in patients with PD, plausibly by recruiting neural networks other than the basal ganglia, such as those in cerebellum. The purpose of this study was to determine whether these adaptive effects persist after a week following visuomotor training in patients with PD and can favorably transfer to other functional writing and drawing tasks. Thirteen patients with Parkinson's disease and twelve healthy, age-matched subjects practiced handwriting either under gradually manipulated (intervention) or intact (placebo) visual display of handwriting size. The results from this study show for the first time, that these adaptive effects may persist for at least up to a week in PD; however, a single training session seemed inadequate to transfer these acquired changes to paper-pen writing and drawing. Additionally, experimental manipulation of task demands during training also helped maintain movement quality in patients with PD as against the placebo group. These findings have important implications in designing rehabilitative interventions to enhance functional sensorimotor performance in patients with PD.Item The Dynamics of Multi-sensory Re-weighting in Healthy and Fall-prone Older Adults(2006-08-04) Allison, Leslie K.; Jeka, John J.; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Multi-sensory re-weighting (MSR) is an adaptive process that prioritizes the visual, vestibular and somatosensory inputs that provide the most reliable information when environmental conditions change. This process is thought to degrade with increasing age, and to be particularly deficient in fall-prone versus healthy older adults. This dissertation presents three studies designed to investigate age- and fall-related changes in MSR. The first study examined the assumption of impaired MSR in healthy and fall-prone older adults using a two-frequency touch/vision experimental design with stimuli at varying amplitudes. Both healthy and fall-prone older adults demonstrated the same pattern of adaptive gain changes as healthy young adults. No group differences in the overall levels of vision and touch gain were found. These results suggest that, for small amplitude vision and touch stimuli, the central sensory re-weighting adaptation process remains intact in healthy and fall-prone older adults. In the second study the effects of a sensory-challenge balance exercise program on laboratory measures of MSR and clinical measures of balance were investigated. Following the intervention the normal adaptive pattern of gain change was unaltered, while declines in overall vision and touch gains that reflect down-weighting of the sensory stimuli were seen. Improvements in four clinical balance measures were observed. These findings indicate that MSR processes in fall-prone older adults are modifiable, that sensory challenge balance exercises may facilitate the ability to down-weight unstable sensory inputs, and that these effects may generalize to other components of balance. A third study explored the dynamics of sensory re-weighting in healthy and fall-prone older adults. Absolute levels of gain, and the rate of adaptive gain change, were examined before and after large changes in visual motion stimulus amplitude. Compared to young adults, gains in both older adult groups were higher when the stimulus amplitude was high, and gains in the fall-prone elderly were higher than both other groups when the stimulus amplitude was low. Both older groups demonstrated slowed sensory re-weighting over prolonged time periods when the stimulus amplitude was high. These results reflect age- and fall-related changes in the extent and rate of down-weighting unstable visual inputs.