School of Public Health

Permanent URI for this communityhttp://hdl.handle.net/1903/1633

The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

Note: Prior to July 1, 2007, the School of Public Health was named the College of Health & Human Performance.

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Subject: search.filters.subject.Neurosciences

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Now showing 1 - 10 of 24
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    HIPPOCAMPAL GLUCOSE TRANSPORT AND OXIDATION IN RESPONSE TO DISRUPTED BLOOD FLOW IN AN AGING RAT MODEL OF HEART FAILURE
    (2023) Pena, Gabriel Santiago; Smith, J. Carson; Kuzmiak-Glancy, Sarah; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The primary objective of this dissertation was to investigate, in a rodent model of cardiovascular disease promoted by transverse aortic constriction (TAC), whether cerebral hypoperfusion stemming from chronic high pulsatile blood flow, and cerebral hypoperfusion stemming from low cerebral blood flow differentially affected hippocampal glucose transport and hippocampal mitochondrial function. We first, characterized the changes in right and left carotid hemodynamics and diameter in response to TAC and in a SHAM control group at three different time points (20-, 30-, and 40 weeks) post-surgery. Then, right, and left hippocampal mitochondrial content and substrate oxidation were investigated, and protein expression of glucose transporters and mitochondrial quality control markers were quantified. In this study, both the SHAM and TAC conditions included male and female rats to address possible sex differences. We report that all time points within TAC, right carotid blood flow velocities and pulsatility were greater than the left, but did not worsen over time. No differences in mitochondrial content were found within TAC nor between TAC and SHAM, but within TAC animals there were impairments in right hippocampal coupled and uncoupled respiration when compared to the left. When compared to the SHAM controls, right and left hippocampi of TAC animals had higher protein expression of mitochondrial quality control markers, but no differences in glucose transporter expression were found. Thus, while both high blood flow and/or pulsatility as well as low cerebral blood flow may lead to brain hypoperfusion, the metabolic consequences of the two may not be the same. The results from this dissertation contribute to the expanding literature characterizing the intersection between cardiovascular disease and neurodegeneration.
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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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    CARDIORESPIRATORY FITNESS AND BASAL FOREBRAIN CHOLINERGIC NETWORKS IN OLDER ADULTS
    (2021) Won, Junyeon; Smith, J. Carson; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    BACKGROUND: Age-related cholinergic dysfunction within the basal forebrain (BF) is associated with cognitive decline and Alzheimer’s disease (AD) in older adults. Accumulating evidence suggests that higher cardiorespiratory fitness (CRF) is linked to neuroprotective effects. However, we have yet to understand the associations between CRF, BF cholinergic function, and cognitive function in older adults. In humans, resting state functional connectivity (rsFC) using functional MRI (fMRI) is useful to characterize the functional aspect of the BF cholinergic connectivity. PURPOSE: 1) To investigate the relationships between CRF-BF rsFC, CRF-cognitive performance, and BF rsFC-cognitive performance in older adults; 2) To investigate the moderating effects of CRF in the relationship between BF rsFC and cognitive function; 3) To investigate the possibility of BF rsFC as a neurophysiological mechanism underpinning the association between CRF and cognitive function in older adults. METHODS: We utilized a publicly available dataset from the Nathan Kline Institute Rockland Sample in which CRF, cognitive test scores (e.g., Rey Auditory Verbal Learning Test, Delis-Kaplan color-word Interference test, and D Delis-Kaplan trail making test), and fMRI data are available in a large sample of older adults. Resting-state fMRI were preprocessed using a rigorous method and valid image processing software. Linear regression models were used to assess the associations between CRF, BF rsFC, and cognitive performance in Specific Aim 1. Sex-dependent differences in the BF rsFC were also investigated as a post-hoc analysis. The interaction between CRF and BF rsFC on cognitive performance was tested using linear regression and analysis of covariance (ANCOVA) for Specific Aim 2. Mediation analysis was administered to examine the possible mediating role of BF rsFC in the relationship between CRF and cognitive function (Specific Aim 3). RESULTS: There was an association between higher CRF and greater NBM rsFC in older adults. There were significant correlations between CRF, CRF-related NBM rsFC, and trail making test performance only in women. Importantly, higher CRF was associated with better Trail Making performance through greater NBM rsFC in females. Lastly, higher CRF was associated with a greater positive association between NBM rsFC and Color-Word Interference performance in older women. CONCLUSION: Higher CRF is associated with greater NBM rsFC in older adults. The association between higher CRF and better executive function performance, however, was evident only in females. Our results further provide evidence that the NBM rsFC may be an underlying neural mechanism in the relationship between CRF and executive function specifically in older women. Hence, sex differences may exist within the CRF-related neuroprotective effects on the NBM functional network and executive function.
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    Cerebral Cortical Networking for Mental Workload Assessment during Practice of a Novel Motor Skill
    (2021) Galway, William; Gentili, Rodolphe; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Although many studies have investigated mental workload during performance, its examination through functional connectivity during motor practice/learning is limited thus requiring further investigations. Therefore, this work aims to examine performance and functional connectivity dynamics underlying mental workload during motor practice by combining a robust computational method to derive connectivity and a human-machine interface which mitigates the use of participants’ prior motor experience since it can bias the acquisition process. Participants practiced reaching with a robotic arm through a head-controlled interface while kinematics and EEG were collected. The robotic end-effector kinematics quantified the performance and the Weighted Phase Lag Index indexed the connectivity during movement planning. Although performance improved during practice, the functional connectivity dynamics suggest that the recruitment of cognitive- motor resources decreased to a certain extent but that further training is likely needed to attenuate the mental workload. The work can also inform the training and design of assistive devices.
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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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    Muscular Fatigue Influences Motor Synergies During Push-ups
    (2018) Bell, Elizabeth M; Shim, Jae Kun; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This research used the push-up as an experimental paradigm for the study of adaptations in motor synergies throughout the challenge of muscular fatigue. Fatigue was expected to lead to greater synchronization of power production (greater motor synergy) by the Central Nervous System (CNS). Greater between and within-limb synergies would be necessary to overcome the reduced force production of fatigued muscles. Different changes in joint power synergies were expected for eccentric and concentric phases due to muscle properties and direction of gravity. Eleven subjects performed push-ups repetitions to self-selected failure. Subjects initially performed push-ups using positive between and within-limb joint power synergies, however synergies reduced throughout reps. Congruent with hypotheses, between and within-limb synergy reduced at a lesser rate throughout eccentric movements. The strategy used relied on bilateral elbow and shoulder joint production. The CNS was not able to adapt control strategies, but instead the dominant strategy was affected throughout fatigue.
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    INVESTIGATIONS TO UNDERSTAND THE UNDERLYING BRAIN PROCESSES WHICH ENHANCE COGNITIVE-MOTOR LEARNING AND PERFORMANCE
    (2018) Jaquess, Kyle James; Hatfield, Bradley D; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The ability to effectively and efficiently process task-relevant information is a critical element to a wide range of cognitive-motor activities. Indeed, various studies have illustrated that elite performers exhibit more refined neuro-cognitive processes than novices. However, it is unclear how these neuro-cognitive information processing abilities develop as skill is acquired. In this dissertation, I provide some evidence to address this gap in the literature. Study 1, entitled “Empirical evidence for the relationship between cognitive workload and attentional reserve” (Jaquess et al., 2017), provided evidence illustrating the relationship between mental workload and attentional reserve. Study 2, entitled “Changes in mental workload and motor performance throughout multiple practice sessions under various levels of task difficulty”, builds from the knowledge gained from Study 1 and extends it to a cognitive-motor learning/practice context over the course of four days. Finally, Study 3, entitled “How engaged are you? An investigation of the neurocognitive mechanisms of self-controlled practice during cognitive-motor learning”, was built upon the knowledge gained from Study 2 to further investigate how aspects of the practice environment, specifically the aspect of control, impact cognitive load and learning outcomes. Broadly, these studies illustrate how some of the neuro-cognitive processes related to information processing in cognitive-motor skills, specifically elements of the electroencephalogram (EEG), change with learning and the acquisition of skill.
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    A NEW APPROACH TO ASSESS HIGH LEVEL PLANNING UNDERLYING COGNITIVE-MOTOR PERFORMANCE DURING COMPLEX ACTION SEQUENCES
    (2018) Hauge, Theresa Christine; Gentili, Rodolphe J; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    While much work has examined low-level sensorimotor planning, only limited efforts have studied high-level motor planning processes underlying the cognitive-motor performance of complex action sequences. Such sequences can generally be successfully executed in a flexible manner and typically involve few constraints. In particular, no past study has examined the concurrent changes of high-level motor plans along with those of mental workload and confidence during practice of a novel complex action sequence. To address this gap, first a computational approach providing markers capturing performance dynamics of action sequences during practice had to be developed since past relevant works only employed fairly rough metrics. Such an approach should provide concise performance markers (e.g., distances, scalar) while still capturing accurately the changes of structure of high-level motor plans during the acquisition of novel complex action sequences. Thus, by adapting the Levenshtein distance (LD) and its operators to the motor domain, a computational approach was first proposed to assess in detail action sequences during an imitation practice task executed by various performers (humans, a humanoid robot) and with flexible success criteria. The results revealed that this approach i) could support accurately comparing the high-level plans generated between performers; ii) provides performance markers (LD, insertion operator) able to differentiate optimal (using a minimum of actions) from suboptimal (using more than a minimum of actions but still reaching the task goal) sequences; and iii) gives evidenced that the deletion operator is a marker of action sequence failure. This computational approach was then deployed to examine during practice the concurrent changes in high-level motor plans underlying action sequence execution with modulation of mental workload and an individual’s confidence in performing the task. The results revealed that as individuals practiced, performance improved (reduction of LD, insertion/substitution and movement time) while the level of mental workload and confidence decreased and increased, respectively. Also, by late practice the sequences were still suboptimal while being executed faster, possibly suggesting different dynamics between the generation of high-level motor plans and their execution. Overall, this work complements prior efforts to assess complex action sequences executed by humans and humanoid robots in the context of cognitive-motor practice, and it has the potential to inform not only human cognitive-motor mechanisms, but also human-robots interactions.
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    The Impact of Acute Aerobic Exercise on Semantic Memory Activation in Healthy Older Adults
    (2018) Won, Junyeon; Smith, Jerome C; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Background: A growing body of exercise literature use functional magnetic resonance imaging (fMRI) technique to measure the effects of exercise on the brain. Findings suggest that regular participation of long-term exercise is associated with enhanced cognitive function. However, fundamental questions regarding the beneficial effects of acute exercise on semantic memory have been ignored. Purpose: This study investigated the effects of a single session of exercise on brain activation during recognition of Famous names and Non-Famous names compared to seated-rest in healthy older adults (age 65-85) using fMRI. We also aimed to measure whether there are differences in brain activation during retrieval of Famous names from three distinct time epochs (Remote, Enduring, and Recent) following acute exercise. Methods: Using a within-subjects counterbalanced design, 30 participants (ages 55-85) will undergo two experimental visits on separate days. During each visit, participants will engage in 30-minutes of rest or stationary cycling exercise immediately followed by the famous name discrimination task (FNT). Neuroimaging and behavioral data will be processed using AFNI (version 17.1.06) and SPSS (version 23), respectively. Results: HR and RPE were significantly higher during exercise. Acute exercise was associated with significantly greater semantic memory activation (Famous > Non-Famous) in five out of nine regions (p-value ranged 0.027 to 0.046). In an exploratory epoch analysis, five out of 14 brain regions activated ruing the semantic memory task showed significantly greater activation intensity following the exercise intervention (Enduringly Famous > Non-Famous). Conclusions: Enhanced semantic memory processing is observed following acute exercise, characterized by greater fMRI response to Famous than Non-Famous names. Enduringly Famous names exhibited significantly greater activation after exercise compared to Non-Famous names. These findings suggest that exercise may improve semantic memory retrieval in healthy older adults, and may lead to enhancement of cognitive function.
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    NEURAL CONTROL OF SPEED IN HUMAN WALKING
    (2018) Ehtemam, Farzad; Kiemel, Tim; Hatfield, Bradley D; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The central nervous system in humans continuously controls the speed of walking by modulating muscle activities. The underlying mechanisms of this control process are not well understood. Recent studies have probed the neural control of walking using sensory and mechanical perturbations. It has been suggested that transient responses to perturbations show patterns in the modulation of muscle activations not previously observed. This dissertation aims to systematically investigate differences in modulations of muscle activations between transient responses and steady-state walking. Three studies were designed to explore these modulations using visual and mechanical perturbations. The first study compared the qualitative patterns from transient responses to visual perturbations to those observed during steady-state walking. Small changes in the average muscle activations between two steady-state speeds were compared to small transient changes due to perturbations. We demonstrated that the decrease in the plantarflexor activity during transient responses that potentially contributed to an increase in speed was unique to these responses and not reproducible in steady-state walking conditions. The second study quantified the effects of average walking speed on transient responses to visual perturbations and compared these effects to steady-state walking conditions. A scaling effect on the amplitude of responses was shown across different treadmill speeds. Finally, in the last study, we explored characteristics of transient responses to mechanical perturbations of the treadmill. We examined the effects of perturbations at two different amplitudes on both kinematics and muscle activations. The responses of the neurofeedback to kinematic deviations were quantified and it was shown that the local limit cycle approximation was reasonable to describe the system. Together these studies shed light on how modulations of muscle activity are utilized by the nervous system to regulate the key variable of walking speed, as well as other aspects of human locomotion.