Browsing by Subject "transcranial magnetic stimulation"
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Item Combining TMS and EEG for Characterizing Motor Network Interactions and Improving Motor Recovery after Stroke(2016-12) Johnson, NessaImaging of electrophysiological activity within the brain is crucial to understanding function in both healthy and disease conditions. The overall goal of this dissertation is to use both non-invasive neuromodulation and non-invasive neuroimaging to characterize and manipulate underlying neurological network dynamics in both healthy and stroke affected subjects. The two main applications of work are for the evaluation of peripheral motor activity on motor network dynamics in healthy subjects, and as a brain-based treatment for motor recovery after stroke. Combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG) imaging can be used to analyze cortical reactivity and connectivity of underlying brain networks. However, the effect of corticospinal and peripheral muscle activity on TMS-evoked potentials (TEPs), particularly in motor areas, is not well understood. One aim of the present dissertation is to evaluate the relationship between cortico-spinal activity, in the form of peripheral motor-evoked potentials (MEPs), and the TEPs from motor areas, along with the connectivity among activated brain areas. This research demonstrates that TMS-EEG, along with adaptive connectivity estimators, can be used to evaluate the cortical dynamics associated with sensorimotor integration and proprioceptive manipulation. Stroke is a devastating neurological disorder which can result in lasting impairment affecting quality-of-life. Combining contralesional repetitive TMS (rTMS) with EEG-based brain-computer interface (BCI) training can address motor impairment after stroke by down-regulating exaggerated inhibition from the contralesional hemisphere and encouraging ipsilesional activation. Another aim of this dissertation was to evaluate the efficacy of combined rTMS+BCI, compared to sham rTMS+BCI, and BCI alone, on motor recovery after stroke in subjects with lasting motor paresis. As evaluated in a series of stroke patients, such a brain-based neuromodulatory and imaging approach for rehabilitation could potentially lead to greater understanding of the influence of brain network dynamics in recovery and design of optimal treatment strategies for individual patients. Our findings demonstrate the feasibility and efficacy of not only combined rTMS+BCI but also BCI alone, as demonstrated by significant improvements over time in behavioral and electrophysiological measures. In summary, the present dissertation research developed and evaluated the combination of neuromodulation and neuroimaging for the non-invasive mapping of motor network activities in the diseased and normal brain. Evaluations were conducted in healthy controls to evaluate the influence of peripheral muscle activity on resulting neural network activity, as well as in stroke patients to provide a brain-based treatment for motor rehabilitation. The results obtained suggest the importance of non-invasive spatiotemporal neuroimaging, along with non-invasive neuromodulation, for providing insight into neuroscience questions and providing novel treatments for clinical problems in a brain-based manner.Item Individualized anodal transcranial direct current stimulation increases corticospinal excitability in children with hemiparesis due to early stroke: transcranial magnetic stimulation assessment data(2020-06-10) Nemanich, Samuel T; Lench, Daniel H; Sutter, Ellen N; Kowalski, Jesse L; Francis, Sunday; Meekins, Greg; Krach, Linda; Feyma, Tim; Gillick, Bernadette T; gillick@umn.edu; Gillick, Bernadette T; University of Minnesota Gillick Pediatric Neuromodulation LaboratoryItem Noninvasive Neuroimaging Of Responses To Transcranial Magnetic Stimulation(2018-05) Cline, ChristopherTranscranial magnetic stimulation (TMS) and electroencephalography (EEG) provide means to noninvasively measure and modulate activity in the brain. EEG has the potential to infer user intent from measured signals, making it possible to build brain-computer interfaces for augmentative and alternative communication and control of devices that do not rely on intact motor function. TMS offers the ability to transiently perturb neural activity with good temporal and spatial precision, and to modulate longer-term excitability and network function, with various applications in both neuroscientific research and clinical treatment. However, both EEG and TMS have limitations, due in a large part to their noninvasiveness. EEG-based BCIs face issues with inconsistent inference of intent estimated from low-SNR measurements, which degrades the speed and accuracy of BCI control. Likewise, current TMS approaches face issues with variability in responses to stimulation, based on lack of precise targeting information and knowledge of underlying mechanisms of stimulation effects, resulting in inefficient or inconsistently effective clinical neuromodulation interventions. In this work, I describe several efforts to address these issues using approaches combining TMS and EEG. To improve our understanding of factors influencing successful motor imagery based BCI control, I applied TMS targeted at perturbing specific neural circuits and measuring resulting changes in BCI control. Conversely, I also explored factors influencing responses to TMS and how EEG can be used to inform stimulation via measurements of stimulation response and estimation of pre-stimulation brain state.Item Optimization of Repetitive Transcranial Magnetic Stimulation With Priming In Chronic Stroke(2014-12) Cassidy, JessicaPurpose: Stroke is leading cause of long-term disability in the United States. The direct destruction of neural tissue from stroke combined with imbalances in transcallosal-mediated interhemispheric inhibition complicate motor recovery. Repetitive transcranial magnetic stimulation (rTMS) is thought to condition surviving but dormant neurons in the ipsilesional primary motor cortex (M1) region to become more amenable to voluntary recruitment during affected extremity movement. Low-frequency rTMS suppresses hyperexcitability in the contralesional hemisphere which can "disinhibit" the ipsilesional hemisphere resulting in greater ipsilesional M1 excitability. A bout of high-frequency excitatory rTMS, referred to as priming, potentiates the suppressive effects of low-frequency rTMS in healthy individuals. The objective of this study was to compare changes in brain excitability and affected hand function following three different rTMS treatments to ascertain whether potential gains from priming stimulation translate to the stroke brain. Methods: Eleven adults (3 females, mean age ± SD = 66 ± 9.4 years) with chronic stroke received three treatments (active 6-Hz priming + active 1-Hz rTMS, active 1-Hz priming + active 1-Hz rTMS, and sham 6-Hz priming + active 1-Hz rTMS) to contralesional M1 in random order over a five-week course with a one-week washout period between treatments. Cortical excitability including interhemispheric inhibition, short-interval intracortical inhibition, intracortical facilitation, and cortical silent period measures along with affected hand function were analyzed using a mixed effects linear model. The model checked for carryover, treatment-by-period interactions, and baseline differences before analyzing within- and between-treatment differences from baseline. Results: Active 6-Hz primed 1-Hz rTMS produced significant within-treatment differences in short-interval intracortical inhibition and cortical silent period duration from baseline indicating reduced intracortical inhibition. Compared to active 1-Hz and sham 6-Hz primed 1-Hz rTMS, active 6-Hz priming generated significantly greater decreases in cortical silent period duration. Discussion: The utility of priming in stroke does not present in such a straightforward manner as it does in healthy individuals given that active 6-Hz priming did not potentiate all outcome measures. Several potential factors are discussed. Our significant findings support the existence of `synaptic wisdom' in the stroke brain involving the deployment of homeostatic and/or metaplastic processes that preserve synaptic function.