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.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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Subject: search.filters.subject.Human Performance

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    HACKING THE NERVOUS SYSTEM: PROMOTION OF PSYCHOMOTOR EFFICIENCY THROUGH VAGUS NEUROMODULATION
    (2021) Lu, Calvin; Hatfield, Bradley D; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Research in performance optimization aims to improve cognitive-motor performance under arduous conditions. From a kinesiology perspective, effectiveness in performance optimization can be quantified through the neurophysiological economy of goal-directed motor behavior. Derived from the psychomotor efficiency hypothesis, the cognitive-affective-motor (CAM) model discusses the brain's complex intersections of cognitive-motor and cognitive-affective processes. The CAM model subscribes to the principle that superior performance is achieved by minimizing nonessential motoric processes, such as mental stress management. When stress response becomes unmanageable, there will be an elevation in nonessential motoric processes and negatively impact motor preparation. The resulting disfluency within the central nervous system will ultimately manifest in the motor and autonomic sections of the peripheral nervous system. To combat the disruptive effects of mental stress, employing autonomic regulation techniques such as Vagus nerve neuromodulation can remedy the inefficiencies of the nervous systems and promote an adaptive state for performance. This dissertation aimed to assess the CAM model empirically by investigating the integrative model of the cortical, autonomic, and motor nervous systems during a precision motor task (i.e., dart-throwing). A thorough examination was conducted on preserving the nervous system’s efficiency and positive impacts on the quality of motor performance through Vagus nerve neuromodulations. Specifically, the study focused on varying levels of mental stress to determine inoculation capabilities. Twenty-three participants were enrolled in a repeated-measures within-subjects design. Neurophysiological measures of nervous system activity were captured before motor execution to determine the amalgamated influence of Vagus nerve neuromodulation and mental stress. The observed results revealed an elevation in psychomotor efficiency through the Vagus nerve neuromodulations. Participants exhibited improved performance, as seen through a reduction of accuracy variability. This was accompanied by nervous system alterations of increased left temporal alpha power, reduced motor unit engagements, and reduced mental workload during the preparation of motor execution. In summary, the observed effects of Vagus nerve neuromodulation techniques successfully promoted nervous system efficiency and an adaptive state for goal-directed motor behavior. The dissertation outcomes provide evidence on the benefits of ergonomic aids such as Vagus nerve neuromodulation on facilitating an adaptive nervous system to enhance cognitive-motor performance.
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    Integrating Human Performance Models into Early Design Stages to Support Accessibility
    (2021) Knisely, Benjamin Martin; Vaughn-Cooke, Monifa; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Humans have heterogeneous physical and cognitive capabilities. Engineers must cater to this heterogeneity to minimize opportunities for user error and system failure. Human factors considerations are typically evaluated late in the design process, risking expensive redesign when new human concerns become apparent. Evaluating user capability earlier could mitigate this risk. One critical early-stage design decision is function allocation – assigning system functions to humans and machines. Automating functions can eliminate the need for users to perform risky tasks but increases resource requirements. Engineers require guidance to evaluate and optimize function allocation that acknowledges the trade-offs between user accommodation and system complexity. In this dissertation, a multi-stage design methodology is proposed to facilitate the efficient allocation of system functions to humans and machines in heterogeneous user populations. The first stage of the methodology introduces a process to model population user groups to guide product customization. User characteristics that drive performance of generalized product interaction tasks are identified and corresponding variables from a national population database are clustered. In stage two, expert elicitation is proposed as a cost-effective means to quantify risk of user error for the user group models. Probabilistic estimates of user group performance are elicited from internal medicine physicians for generalized product interaction tasks. In the final stage, the data (user groups, performance estimations) are integrated into a multi-objective optimization model to allocate functions in a product family when considering user accommodation and system complexity. The methodology was demonstrated on a design case study involving self-management technology use by diabetes patients, a heterogeneous population in a safety-critical domain. The population modeling approach produced quantitatively and qualitatively validated clusters. For the expert elicitation, experts provided internally validated, distinct estimates for each user group-task pair. To validate the utility of the proposed method (acquired data, optimization model), engineering students (n=16) performed the function allocation task manually. Results indicated that participants were unable to allocate functions as efficiently as the model despite indicating user capability and cost were priorities. This research demonstrated that the proposed methodology can provide engineers valuable information regarding user capability and system functionality to drive accessible early-stage design decisions.
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    Examination of the Brain Processes Underlying Emotion Regulation within a Stress Resilient Population
    (2011) Costanzo, Michelle Elizabeth; Hatfield, Bradley D.; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Emotion robustly affects the quality of cognitive-motor performance under conditions of mental stress. As such, the regulation of emotion is critical to successful execution of motor skills during emotional challenge. Previous investigations of the stress-performance relationship have typically focused on behavioral outcomes, however, few have adopted a cognitive neuroscience approach to examine the involved mechanisms underlying this relationship. Furthermore, it is unclear if individuals who have a history of superior performance under stress (stress resilient population) exhibit brain responses characterized by an efficiency of neural processing and an adaptive emotion regulatory strategy. Using functional magnetic resonance imaging (fMRI), the present study examined activation in critical brain regions during affective challenge (i.e., presentation of International Affective Picture System negative images and Sport-Specific negative images) in 13 elite athletes (intercollegiate football players who have demonstrated successful execution of cognitive-motor skills under mental stress) relative to an age-matched control group (n=12). The present dissertation is organized into three main sections. The first report, entitled Brain Processes during Motor Performance under Psychological Stress, an Independent Component Analysis of EEG, is an examination of brain processes during competitive stress. This study revealed non-essential neuromotor cerebral cortical noise with a quantified increase in complexity during a cognitive-motor task. The second report is entitled Efficiency of Affective Brain Processes in Expert Cognitive-Motor Performers during Emotional Challenge. This fMRI examination of elite athletes revealed processing economy in brain regions critical to self regulation, management of emotional impulses and social cognition. The third report, entitled The Specificity of Neural Regulatory Processes during Emotional Challenge in a Stress Resilient Population, examined with fMRI if elite athletes spontaneously engage in cognitive reappraisal during the presentation of arousing sport-specific images. Results suggest that elite athletes process sports-relevant affective information in an automatic manner, congruent with a cognitive reappraisal strategy, which neutralized the negative impact of the scenes. In conclusion, the results suggest that elite performers are important models of stress resilience and respond not only in an efficient manner to stressful events, but demonstrate an adaptive regulatory response when challenged within their domain of experience.