Browsing by Author "Riley, Zachary"

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    Application of Transcranial Direct Current Stimulation During Motor Skill Acquisition
    (2024-03) Meek, Anthony Wilhite; Riley, Zachary; Munk, Niki; Naugle, Kelly; Streepey, Jake
    Transcranial direct current stimulation has been used to influence the acquisition of motor skills; however, most studies investigate relatively simple laboratory based motor skills tasks. Since the regions where structural and functional changes support motor learning are dependent on the qualities of the task, translation of the findings to real-world skills has been limited. In general, anodal current stimulation is associated with functional facilitation and cathodal current is associated with functional inhibition. The purpose of this dissertation is to explore the effect of transcranial direct current stimulation of the primary motor cortex and the cerebellum upon the acquisition of novel motor skills that possess varied demands comparable to everyday tasks. In order to study motor skill learning, we investigated 4 unilateral tasks made novel by using the non-dominant hand, ensuring a discernible fast phase of learning in which to observe skill acquisition. In study one, anodal stimulation applied over the primary motor cortex during a 20 minute practice session skill acquisition in a complex dart throwing task compared to cathodal motor cortex stimulation or SHAM. In study two, 20 minutes of anodal motor cortical stimulation while practicing a dexterous tweezer task significantly reduced postpractice pin-placing time compared to SHAM. In study three, anodal motor cortical stimulation during 20 minutes practicing a dexterous rhythmic-timing video game led to significantly higher performance scores compared to SHAM. In study four, in the same videogame task, concurrently stimulating the primary motor cortex with 2 milliamp anodal current while stimulating the cerebellum with 2 milliamp cathodal current during 20 minutes of practice led to significantly higher performance scores compared to SHAM, whereas 2 milliamp anodal primary motor cortex, anodal cerebellar, and cathodal cerebellar stimulation alone was not different than SHAM. These data altogether show that motor cortical transcranial direct current stimulation can facilitate skill acquisition in everyday tasks with a range of gross, fine, and visuomotor demands. They also provide the first evidence of a synergistic effect on motor learning from concurrent primary motor cortex and cerebellar stimulation, which may contribute to the development of novel stimulation protocols.
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    The Effect of Anterior Cruciate Ligament Reconstruction on Leg-Spring Stiffness During Hopping
    (2020-12) Wolfe, David K.; Bahamonde, Rafael; Streepey, Jefferson; Riley, Zachary; Naugle, Kelly; Beekley, Matthew
    Leg-Spring Stiffness (LSS) is the measure of the musculoskeletal, neuromuscular, and biomechanical functions of the human body, and an appropriate evaluation metric for changes brought on by Anterior Cruciate Ligament Reconstruction (ACLr). ACLr can lead to flexion and extension loss, resulting in increased stiffness of the musculotendinous units of the ACLr leg and thus changes in LSS. LSS can be measured using Kleg, but little is known about the validity and reliability of the different methods of LSS and Kleg calculations. The purpose of this study was to determine if ACLr leads to a change in LSS (as measured by Kleg) during hopping, and to compare results of the Spring-Mass calculation and knee Joint Torsional stiffness methods in the computation of the overall Kleg. Video data synchronize with GRF were used to compute the kinematic and kinetic variables. Mann-Whitney U tests were used to determine significant differences between the control and experimental group for the Spring-Mass method of calculation (p = 0.004), Joint Torsional method (p =0.44), Kknee (p = 0.29), and Kankle (p = 0.17). Cohen’s effect calculations showed small to medium effects for the KKnee, (d = 0.383) but moderate effect size for the KAnkle, (d = 0.541). Wilcoxon Signed Rank comparison for all the legs and (N=42) between computational methods were significant differences between computational methods (Z = 5.65, p = 0.000), and with a large effect size (Cohen’s d = 3.14). Similar results were found when comparing only the ACLr leg values (p = 0.005, Cohen’s d = 4.88). The comparison between ACL Leg vs Non-ACL leg for experimental group subjects was not significant in either calculation method (Spring-Mass p = 0.20, Z = -1.27; torque calculation p = 0.96, Z = -0.05). The spring-mass method was more stable and able to detect differences between the control and ACLr group. The lack of statistical differences in the joint torsion calculation method, as well as in comparing the unaffected leg to the ACLr leg in the experimental group, suggests that LSS may not be a precise enough measurement to determine the effects of an ACLr.
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    Greater functional aerobic capacity predicts more effective pain modulation in older adults
    (Office of the Vice Chancellor for Research, 2016-04-08) Ohlman, Tom; Naugle, Keith; Keith, NiCole; Riley, Zachary; Naugle, Kelly M.
    Endogenous pain inhibitory and facilitory function deteriorates with age, potentially placing older adults at greater risk for chronic pain. Prior research shows that self-reported physical activity predicts endogenous pain inhibitory capacity and facilitation of pain on quantitative sensory tests (QST) in healthy adults. Purpose: To investigate whether functional aerobic capacity and lower extremity strength in older adults cross-sectionally predicts pain sensitivity, pain inhibition following isometric exercise, and facilitation of pain during heat pain temporal summation (TS) tests. Methods: 42 subjects (10 male, 32 female, age=67.5±5.1) completed the 6-minute walk test (6MWT), 30-second chair stand test, and several QSTs. QSTs included: 1) Pain ratings (0-100 scale) during the submersion of the hand in a cold water bath (CWB), 2) heat pain threshold tests, 3) the amount of pain reduction following submaximal isometric exercise, and 4) degree of pain facilitation during temporal summation tests conducted at 44, 46, and 48°C. Responses on the QSTs were analyzed using hierarchical linear regression with meters on 6MWT and number of chair stands as final predictors. Results: After controlling for demographic and psychological factors, aerobic capacity on 6MWT significantly predicted CWB pain ratings (R2 change= 22.5%, Beta= -0.491), pain facilitation during TS trials at 44°C (R2 change= 16.7%, Beta= -0.446), and the amount of pain reduction following isometric exercise (R2 change= 20.7%, Beta= 0.393). All other analyses were not significant (P>0.05). Conclusions: Older adults exhibiting greater functional aerobic capacity displayed reduced cold pain sensitivity, reduced pain facilitory function, and increased pain inhibition following exercise. These findings suggest that increased aerobic fitness in older adults may be associated with more effective endogenous modulation of pain. This study was funded by the IUPUI School of PETM Faculty Research Opportunity Grant.
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    Multifocal Transcranial Direct Current Stimulation to Modulate Motor Learning
    (2025-03) Greenwell, Davin Ross; Riley, Zachary; Kaleth, Anthony; Naugle, Kelly; Streepey, Jake; Metzler-Wilson, Kristen
    Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that modulates neural excitability in targeted brain regions, influencing processes such as motor learning. While tDCS has been previously shown to benefit motor skill acquisition, much of this research has focused on relatively simple, unimanual tasks. Conversely, the effects of tDCS on more complex, bimanual motor tasks remain understudied, with existing findings often yielding mixed results. This inconsistency poses challenges for translating laboratory findings to functional, real-world motor skills, which frequently involve coordinated, two-handed movements and heightened cognitive demands. Emerging evidence suggests that multifocal tDCS paradigms, which simultaneously target multiple brain regions, may provide enhanced learning effects, particularly for complex motor tasks. Unlike traditional monofocal stimulation protocols that focus on the primary motor cortex (M1) or cerebellum individually, multifocal approaches may better address the neural dynamics underlying bimanual coordination and interhemispheric interactions. The purpose of this dissertation was to investigate the potential of multifocal tDCS to enhance motor learning in complex tasks, examining both unimanual and bimanual skill acquisition. This research involved a series of studies beginning with monofocal tDCS applied to M1 and the cerebellum during a non-dominant unimanual rhythm-timing task and culminating in a multifocal “tri-focal” stimulation protocol during a bimanual motor learning task. In Study One, we compared the effects of excitatory M1 stimulation against excitatory and inhibitory cerebellar and sham stimulation. While none of the monofocal tDCS conditions significantly enhanced learning compared to sham, small, non-significant trends were observed which informed the design of Study Two. Here, we observed that combining excitatory M1 stimulation with inhibitory cerebellar stimulation resulted in significant and robust improvements in motor learning. In Study Three, we found that bilateral M1 stimulation significantly enhanced the early stages of bimanual skill learning at lower intensities. However, Study Four revealed that increasing stimulation intensity or adding inhibitory cerebellar stimulation impaired bimanual learning. Together, these findings contribute to a growing understanding of how multifocal stimulation paradigms can be tailored to enhance motor learning in real-world tasks while underscoring the importance of carefully optimizing stimulation parameters to task-specific demands.
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    The Validity and Reliability of the PAVS and IPAQ-SF as Physical Activity Assessment Tools in Patients with Obstructive Sleep Apnea
    (2020-01) Adolphs, Max W.; Kaleth, Anthony; Keith, NiCole; Riley, Zachary; Warden, Stuart
    Efforts to encourage the medical community to prescribe exercise for disease prevention and management have increased significantly in recent years. In patients with obstructive sleep apnea (OSA), it is encouraging that exercise has been shown to improve sleep efficiency, daytime sleepiness, and disease severity. However, in order to better understand the dose-response relationship between exercise and OSA-related outcomes, accurate and reliable methods for assessing physical activity habits are needed. Purpose: To determine the test-retest reliability and validity of two self-report physical activity questionnaires [Physical Activity Vital Sign (PAVS); International Physical Activity Questionnaire-Short Form (IPAQ-SF)] in an OSA population. Methods: 39 adults with moderate-to-severe OSA wore an accelerometer for seven consecutive days and completed the PAVS and IPAQ-SF (twice within 10 d), along with questionnaires on quality of life, sleepiness, and treatment adherence. Test-retest reliability was determined using intraclass correlation coefficients (ICC). Criterion and construct validity were determined using Pearson (r) and Spearman correlation coefficients (ρ), respectively. Results: PAVS and IPAQ-SF scores were reported as total min/wk of moderate-vigorous physical activity (MVPA). Test-retest reliability for MVPA was excellent for PAVS (ICC = 0.982) and good for IPAQ-SF (ICC = 0.766). MVPA assessed via accelerometry was strongly correlated with PAVS (r = 0.802) and moderately with IPAQ-SF (r = 0.569). Both PAVS and IPAQ-SF were significantly correlated with body mass index (BMI) (ρ = -0.273 and -0.268, respectively), but no other variables. Conclusions: The PAVS and IPAQ-SF are reliable and valid PA questionnaires and may be utilized as a tool for accurately assessing physical activity levels in OSA patients.