Dissertations and Theses

Date of Award


Document Type



Biomedical Engineering

First Advisor

Marom Bikson


Magnetic Resonance Imaging (MRI), Diffusion Tensor Imaging (DTI), Pulsed Arterial Spin Labeling (pASL), Blood-Brain Barrier (BBB)


Transcranial Direct Current Stimulation (tDCS) is a non-invasive method of neuromodulation with applications in neuroscience, clinical care, and biomedical engineering. tDCS has been well established as a safe method of applying low amplitude current between two or more electrodes to alter excitation thresholds and neuroplasticity. Recently, in-vitro and clinical studies have suggested that DC stimulation can induce a transient, polarity-specific, effect of increased water exchange across the blood-brain barrier (BBB). The electroosmotic effect, the proposed phenomenon driving water exchange, is a biophysical response of charged ions moving across an oppositely-charged surface, i.e., the tight junction, when subjected to an electric field. In response, a dual-arm, randomized, crossover trial was designed to study the electrophysiological effects of tDCS on fluid movement throughout the human brain. The goal of this study was to use Diffusion Tensor Imaging (DTI) and pulsed-Arterial Spin Labeling (pASL) to target interstitial fluid diffusion within the brain parenchyma as well as blood perfusion of brain tissue, respectively, with and without intervention of bi-frontal 4mA anodal tDCS. The MRI sequence cascade supported data collection before, during, and after a ~20 min dose of HD-tDCS to compare with complementary sham-current MRI measurements at rest. This study provides the background and motivation of the experimental design, an outlined methodology of MRI data acquisition with concurrent HD-tDCS, detailed parameters of the echo-planar imaging (EPI) sequences, example images, an image-processing pipeline, results, statistical analysis, and an open-source dataset. Analysis was performed on the whole brain, as well as within anatomically symmetric, spherical, regions of interest (ROI) in the dorsolateral prefrontal cortex. This study reports the major finding of increased mean diffusivity (p = 0.03, partial η 2 = 0.42, post-hoc power = 0.95) during HD-tDCS within a localized, targeted, area of electrical stimulation under the anode electrode. This study provides both an open-access, BIDS compliant, dataset of concurrent MRI with HD-tDCS, along with data and analysis to further our understanding of the biophysical effects induced by non-invasive electrical stimulation.



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