Matching Items (6)
Description
Transcranial electrical stimulation (tES) is a non-invasive brain stimulation therapy that has shown potential in improving motor, physiological and cognitive functions in healthy and diseased population. Typical tES procedures involve application of weak current (< 2 mA) to the brain via a pair of large electrodes placed on the scalp. While the therapeutic benefits of tES are promising, the efficacy of tES treatments is limited by the knowledge of how current travels in the brain. It has been assumed that the current density and electric fields are the largest, and thus have the most effect, in brain structures nearby the electrodes. Recent studies using finite element modeling (FEM) have suggested that current patterns in the brain are diffuse and not concentrated in any particular brain structure. Although current flow modeling is useful means of informing tES target optimization, few studies have validated tES FEM models against experimental measurements. MREIT-CDI can be used to recover magnetic flux density caused by current flow in a conducting object. This dissertation reports the first comparisons between experimental data from in-vivo human MREIT-CDI during tES and results from tES FEM using head models derived from the same subjects. First, tES FEM pipelines were verified by confirming FEM predictions agreed with analytic results at the mesh sizes used and that a sufficiently large head extent was modeled to approximate results on human subjects. Second, models were used to predict magnetic flux density, and predicted and MREIT-CDI results were compared to validate and refine modeling outcomes. Finally, models were used to investigate inter-subject variability and biological side effects reported by tES subjects. The study demonstrated good agreements in patterns between magnetic flux distributions from experimental and simulation data. However, the discrepancy in scales between simulation and experimental data suggested that tissue conductivities typically used in tES FEM might be incorrect, and thus performing in-vivo conductivity measurements in humans is desirable. Overall, in-vivo MREIT-CDI in human heads has been established as a validation tool for tES predictions and to study the underlying mechanisms of tES therapies.
ContributorsIndahlastari, Aprinda (Author) / Sadleir, Rosalind J (Thesis advisor) / Abbas, James (Committee member) / Frakes, David (Committee member) / Kleim, Jeffrey (Committee member) / Kodibagkar, Vikram (Committee member) / Arizona State University (Publisher)
Created2017
Description
In this quantitative research paper, we explored the correlation between the six dimensions of motivation as part of the Self-Determination Theory spectrum and physical activity. In addition, our aim was to also see if Transcranial Direct Current Stimulation (tDCS) paired with exercise as an intervention would affect motivation to exercise over time.
ContributorsPankoff, Mia (Author) / Quezada, Gabrielle (Co-author) / Katsanos, Christos (Thesis director) / Shaffer, Zachary (Committee member) / Ruiz Tejada, Anaissa (Committee member) / Barrett, The Honors College (Contributor) / Edson College of Nursing and Health Innovation (Contributor)
Created2021-12
Description
In this quantitative research paper, we explored the correlation between the six dimensions of motivation as part of the Self-Determination Theory spectrum and physical activity. In addition, our aim was to also see if Transcranial Direct Current Stimulation (tDCS) paired with exercise as an intervention would affect motivation to exercise over time.
ContributorsQuezada, Gabrielle (Author) / Pankoff, Mia (Co-author) / Katsanos, Christos (Thesis director) / Shaffer, Zachary (Committee member) / Ruiz Tejada, Anaissa (Committee member) / Barrett, The Honors College (Contributor) / Edson College of Nursing and Health Innovation (Contributor) / College of Integrative Sciences and Arts (Contributor)
Created2021-12
Description
Studies using transcranial direct current stimulation (tDCS) to enhance motor training areoften irreproducible. This may be partly due to differences in stimulation parameters across
studies, but it is also plausible that uncontrolled placebo effects may interact with the true
‘treatment’ effect of tDCS. Thus, the purpose of this study was to test whether there was a
placebo effect of tDCS on motor training and to identify possible mechanisms of such an effect.
Fifty-one participants (age: 22.2 ± 4.16; 26 F) were randomly assigned to one of three groups:
active anodal tDCS (n=18), sham tDCS (n=18), or no stimulation control (n=15). Participant
expectations about how much tDCS could enhance motor function and their general suggestibility
were assessed. Participants then completed 30 trials of functional upper extremity motor training
with or without online tDCS. Stimulation (20-min, 2mA) was applied to the right primary motor
cortex (C4) in a double-blind, sham-controlled fashion, while the control group was unblinded and
not exposed to any stimulation. Following motor training, expectations about how much tDCS
could enhance motor function were assessed again for participants in the sham and active tDCS
groups only. Results showed no effect of active tDCS on motor training (p=.67). However, there
was a significant placebo effect, such that the collapsed sham and active tDCS groups improved
more during motor training than the control group (p=.02). This placebo effect was significantly
influenced by post-training expectations about tDCS (p=.0004). Thus, this exploratory study
showed that there is a measurable placebo effect of tDCS on motor training, likely driven by
participants’ perceptions of whether they received stimulation. Future studies should consider
placebo effects of tDCS and identify their underlying mechanisms in order to leverage them in
clinical care.
ContributorsHAIKALIS, NICOLE (Author) / Schaefer, Sydney Y (Thesis advisor) / Honeycutt, Claire (Committee member) / Daliri, Ayoub (Committee member) / Arizona State University (Publisher)
Created2022
Description
Motor skill learning is important to rehabilitation, sports, and many occupations. When attempting to learn or adapt a motor skill, some individuals learn slower or less compared to others despite the same amount of motor practice. This dissertation aims to understand the factors that contributed to such variability in motor learning, and thereby identify viable methods to enhance motor learning. Behavioral evidence from our lab showed that visuospatial ability is positively related to the extent of motor learning. Neuroimaging studies suggest that motor learning and visuospatial processes share common frontoparietal neural structures, and that this visuospatial-motor relationship may be more pronounced in the right hemisphere compared to the left. Thus, the overall objective of this dissertation is to determine if aspects of motor learning (such as the rate and extent of skill acquisition) may be modifiable through neuromodulation of the right frontoparietal network. In Aim 1, anodal transcranial direct current stimulation (tDCS) was used to test whether modulating the right parietal area affects visuospatial ability and motor skill acquisition. A randomized, three-arm design was used, which added a no-tDCS control group to the double-blinded sham-control protocol to address placebo effects. No tDCS treatment effect was observed, likely due to low statistical power to detect any treatment effects as the study is still ongoing. However, the current results revealed a unique finding that the placebo effect of tDCS was stronger than its treatment effect on motor learning, with implications that tDCS and motor studies should measure and control for placebo effects.
In Aim 2, right frontoparietal connectivity during resting-state EEG was estimated via alpha band imaginary coherence to test whether it correlated with visuospatial performance and motor skill acquisition. As a preliminary step towards leveraging the frontoparietal network for EEG-neurofeedback applications, this work found that alpha imaginary coherence was positively correlated with visuospatial function, but not with motor skill acquisition during a limited dose of motor practice (only 5 trials). This work establishes a premise for developing frontoparietal alpha IC-based neurofeedback for cognitive training in rehabilitation, while warranting future studies to test the relationship between alpha IC and motor learning with a more extensive motor training regimen.
ContributorsWang, Peiyuan (Author) / Schaefer, Sydney Y (Thesis advisor) / Buneo, Christopher A (Committee member) / Abbas, James (Committee member) / Lohse, Keith R (Committee member) / Wyckoff, Sarah N (Committee member) / Arizona State University (Publisher)
Created2021
DescriptionStudy invetsigated impacts of TDCS of the trigeminal region of the face, which resulted in improved reaction times and numerically, though not significantly, larger pupil diameters, indicating increased arousal.
ContributorsPope, Ben Alexander (Author) / Corbin, William (Thesis director) / Brewer, Gene (Committee member) / School of Molecular Sciences (Contributor) / Department of Psychology (Contributor) / Barrett, The Honors College (Contributor)
Created2020-12