Browsing by Subject "tDCS"

Now showing 1 - 5 of 5
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    Interplay among Neural, Autonomic, and Neuroendocrine Systems in Rumination
    (2022-07) Thai, Michelle
    Rumination is a type of perseverative negative cognition that is associated with greater risk for depression and a worse prognosis. Current treatments for depression do not always adequately address symptoms of rumination. Novel, biologically-based treatments need to be developed. To develop such treatments, a thorough understanding of the mechanisms underlying rumination using multilevel approaches is necessary since processes like rumination implicate different neural and physiological systems which may constrain one another or have additive effects. This study took a multiple units of analysis approach to examine 1) neural connectivity and activation in the frontolimbic circuit and Default Mode Network (DMN), 2) heart rate variability (HRV), and 3) basal cortisol levels in the context of awakening in the context of a novel treatment for rumination incorporating mindful breathing training (MBT) and transcranial direct current stimulation (tDCS). This study explored 1) how rumination is related to these three systems and 2) how improvement in rumination relates to changes in these three systems. Overall, we find evidence that mindful breathing and tDCS can reduce rumination and depression as well as change these neurophysiological systems. Although these findings were not always clearly related to improvement in clinical symptoms, we find some evidence that tDCS and mindful breathing can increase HRV, decrease DMN and frontolimbic activation during a rumination induction task, increase frontolimbic RSFC, and increase positive mind wandering, which was generally associated with clinical improvement, generally more so or the tDCS group relative to sham. These results provide preliminary evidence that web-based mindfulness practices may have potential in reducing rumination and changing relevant neurophysiological systems.
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    Modulating Human Cortical Plasticity via Transcranial Direct Current Stimulation: Basic & Clinical Applications
    (2019-12) Boroda, Elias
    As humans we have a unique ability to study, and even to modify the makeup of our own existence. The concept of changing oneself has always intrigued me, and it was what initially piqued my interest in the study of the human brain. In my estimation, the brain was where most of our “existence” derived from (I’ve changed my mind about that somewhat since then), and therefore learning about it, and how to modify it, would be quite an interesting undertaking. My passion for this topic led me to work with Dr. Kelvin Lim, who at the time was building momentum for studying the clinical potential of non-invasive neuromodulation. Over the course of 5 years working with Kelvin, I was able to learn a significant amount regarding neuromodulation, research and science as a whole. This dissertation describes two of my main projects. These studies focus on researching the basic and clinical applications of transcranial direct current stimulation (tDCS) as a means to modulate human brain plasticity. The first project, described in chapter II, was a basic science study which aimed to investigate how tDCS interacts with functional brain state. Previous literature has reported on the ability of tDCS to modulate plasticity, both in humans and in animal models. However, given the non-focal nature of tDCS, there is an open debate as to how specific outcomes (physiological or behavioral) are achieved. Recently, a hypothesis has been proposed that active brain networks or populations of neurons are preferentially susceptible to the influence of electric fields over inactive networks or groups of cells. This ‘activity-selectivity’ hypothesis has not been thoroughly tested in studies using physiological measures. In this study I use a novel electrophysiological paradigm to investigate the impact of tDCS on plasticity in the auditory cortex. The unique features of the paradigm allowed me to analyze stimulus specific effects of tDCS, making it possible to test the ‘activity-selectivity’ hypothesis using a novel physiological measure. The third chapter of the thesis describes a clinical trial where we used tDCS in combination with cognitive training to treat impaired executive functions in children with fetal alcohol spectrum disorders (FASD). Exposure to alcohol in the womb impairs neuroplasticity in the developing brain and often leads to severe cognitive deficits later in life. Cognitive training is one of a few treatment options for these deficits, however treatment times are long and difficult to complete. Research has shown that pairing cognitive training with tDCS enhances efficacy and can allow for a shorter intervention. However, tDCS has not been tried in children with FASD and it is not clear if it would be tolerated or efficacious in this population. With this in mind, we conducted a first of its kind clinical trial in children with FASD to test the tolerability and feasibility of tDCS augmented cognitive training and its effects on executive functioning. In sum, this dissertation describes two of my major studies which describe the characteristics and the use of tDCS in both a basic and clinical setting. I believe that the findings generated by these studies will make a significant and positive effect on the field of tDCS and its use in the clinic.
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    The Role of Transcranial Direct Current Stimulation and Cognitive Training to Decrease Food-Related Impulsivity Behavior in Individuals With Obesity: a Review and Pilot Study
    (2021-05) Salisbury, Madeleine
    Impulsivity has been implicated in refractory obesity. The dorsolateral prefrontal cortex (DLPFC) may counterbalance overactive brain reward by enhancing executive function (EF), including impulse control, mitigating loss-of-control eating. Galioto found that EF predicted weight-loss in structured medical weight-loss programs (Galioto 2016). Cognitive training (CT) monotherapy for EF improvement has not shown sufficient therapeutic promise nor has DLPFC-directed transcranial direct current stimulation (tDCS), but coupled, they may enhance EF. The aim of this study was to determine if tDCS coupled with computerized CT decreased impulsivity in individuals with obesity.
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    Targeting the Brain in Brain-Computer Interfacing: The Effect of Transcranial Current Stimulation and Control of a Physical Effector on Performance and Electrophysiology Underlying Noninvasive Brain-Computer Interfaces
    (2017-07) Baxter, Bryan
    Brain-computer interfaces (BCIs) and neuromodulation technologies have recently begun to fulfill their promises of restoring function, improving rehabilitation, and enhancing abilities and learning. However, lengthy user training to achieve acceptable accuracy is a barrier to BCI acceptance and use by patients and the general population. Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulation technology whereby a low level of electrical current is injected into the brain to alter neural activity and has been found to improve motor learning and task performance. A barrier to optimizing behavioral effects of tDCS is that we do not yet understand how neural networks are affected by stimulation and how stimulation interacts with ongoing endogenous activity. The purpose of this dissertation was to elucidate strategies to improve BCI control by targeting the user through two approaches: 1. Subject control of a robotic arm to enhance user motivation and 2. tDCS application to improve behavioral outcomes and alter networks underlying sensorimotor rhythm-based BCI performance. The primary results illustrate that targeted tDCS of the motor network interacts with task specific neural activity to improve BCI performance and alter neural electrophysiology. This effect on neural activity extended across the task network, beyond the area of direct stimulation, and altered connectivity unilaterally and bilaterally between frontal and parietal cortical regions. These findings suggest targeted neuromodulation interacts with endogenous neural activity and can be used to improve motor-cognitive task performance.
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    Usability Testing For A Non-Functioning Mockup of A Tdcs Stroke therapy System
    (2020-06) Knerr, Jordan
    This study examined the usability of a custom telerehabilitation therapy system for adults with stroke. The system included a non-functioning mockup of a hat that would apply transcranial direct current stimulation (tDCS) to the users. The tDCS would be used in conjunction with a video game that was designed as the mechanism through which physical therapy would be done. The goal of this study was to determine if the therapy system would be easy for adults with stroke to set up and use with a therapist instructing them remotely, but without anyone physically present to assist them. Five therapists and five users were trained on the system and then asked to execute a therapy session. Observations were recorded during the session and participants were interviewed about their experience afterwards. In general, the participants found the system easy to use. Most participants thought it would get easier with more practice. The participants offered suggestions for how to improve the system. These suggestions were categorized and recorded for future implementation. Because proper electrode alignment is critical when it comes to brain stimulation, a repeatability test was also performed with the users. The repeatability data was analyzed using the mean and standard deviations of the tDCS hat placement locations. The data showed that users were able to align the tDCS hat and its electrodes within 0.68 cm, which was below the 1.3 cm acceptance threshold.