UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

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Subject: search.filters.subject.Motor Control

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Now showing 1 - 5 of 5
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    Human-Human Sensorimotor Interaction
    (2019) Honarvar, Sara; Shim, Dr. Jae Kun; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    We investigated the role of sensory feedback in inter-personal interactions when two co-workers are working together. Twenty-five co-workers completed two isometric finger force production experiments. In Experiment 1, co-workers isometrically produced finger forces such that combined force will match a target force and/or torque under different visual and haptic conditions. In Experiment 2, without participants’ knowledge, each performed the same task with the playback of his/her partner’s force trajectory previously recorded from Experiment 1. Results from both experiments indicated that co-workers performed the task worse in the presence of haptic and visual feedback. Since, in latter as opposed to the former condition, they adopted a compensatory strategy to accomplish the task accurately. Further analysis showed that co-workers achieved the same level of motor performance with similar control strategies, suggesting that they did not work synergistically to achieve better performance, but one co-worker processed another as disturbance when they worked together.
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    Lower-Body Mechanical Perturbation of Gait to Identify Neural Control
    (2017) Rafiee, Shakiba; Kiemel, Tim; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Neural feedback plays a key role in maintaining locomotor stability in face of perturbations. In this study, we systematically identified properties of neural feedback that contribute to stabilizing human walking by examining how the nervous system responds to small kinematic deviations away from the desired gait pattern. We applied small continuous mechanical perturbation, forces at the ankles, as well as small continuous sensory perturbation, movement of a virtual visual scene, in order to compare how neural feedback responds to actual and illusory kinematic deviations. Computing phase-dependent impulse response functions (φIRFs) that describe kinematic and muscular responses to small brief perturbations (impulses), enabled us to identify critical phases of the gait cycle when the nervous system modulates muscle activity. In particular, our results suggest that an early-stance modulation of anterior leg-muscles is a general control mechanism that serves multiple functions, including controlling walking speed and compensating for errors in foot placement.
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    THE ORGANIZATION OF MOTOR SYNERGIES IN ONE-PERSON AND TWO-PERSON MULTI-FINGER FORCE PRODUCTION TASKS
    (2017) Christensen, Kelsey Ann; Shim, Jae K; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Humans perform motor tasks every day, both individually and with others. Performing motor tasks involves the organization of motor synergies, task-specific groupings of individual motor effectors that are temporarily constrained to act as a single unit and whose total combined output ensures stability of the overall task performance. Both intra- and inter-personal motor synergies have been found to exist in one-person and two-person motor tasks, respectively. Not as clear, however, is whether separate synergies can exist simultaneously on multiple levels of control within a given task. The purpose of the current study is to investigate the organization of force-stabilizing motor synergies during one-person and two-person finger-force production tasks using the Uncontrolled Manifold Analysis. We expect to find both intra- and inter-personal motor synergies, an increase in synergy strength as tasks require more motor effectors, but the lack of simultaneously-occurring motor synergies on multiple levels of control within the given tasks.
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    Neural Modulation of Leg Stiffness in Response to Neuromuscular Fatigue
    (2016) Chu, Edward; Shim, Jae Kun; Miller, Ross H; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The spring-mass model is able to accurately represent hopping spring-like behavior (leg and joint stiffness), and leg and joint stiffness changes can reveal overall motor control responses to neural and muscular contributors of neuromuscular fatigue. By understanding leg stiffness modulation, we can determine which variables the nervous system targets to maintain motor performance and stability. The purpose of this study was to determine how neuromuscular fatigue affects hopping behavior by examining leg and joint stiffness before and after a single-leg calf raise fatiguing protocol. Post-fatigue, leg stiffness decreased for the exercised leg, but not for the non-exercised leg. Ankle and knee joint stiffness did not significantly change for either leg. This indicates that leg stiffness decreases primarily from muscular fatigue, but was not explained by ankle and knee joint stiffness. The decrease in leg stiffness may be an attempt to soften landing impact, while at the same time maintaining performance.
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    Handwriting Kinetics: A Search for Synergies
    (2008) Hooke, Alexander W.; Shim, Jae Kun; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The purpose of this study was to investigate central nervous system strategies for controlling multi-finger forces in three-dimensional (3-D) space during a circle drawing task. In order to do this the Kinetic Pen, a pen capable of measuring the six-component force and moment of force that each of four individual contacts applies to the pen during writing, was developed. The synergistic actions of the contact forces, defined as kinetic synergy, were investigated in three orthogonal spaces: radial, tangential, and vertical to the circle edge during a circle drawing task. We employed varying directional (clockwise vs. counterclockwise) and pacing (self-paced vs. external-paced) conditions. Results showed that synergies between pen-hand contact forces existed in all components. Radial and tangential component synergies were greater than in the vertical component. Synergies in the clockwise direction were stronger than the counter-clockwise direction in the radial and vertical components. Pace was found to be insignificant in all conditions.