University of Twente Student Theses


Simulation and analysis of E-fields of dual-site tACS at various phase-lag values

Rona, M. (2022) Simulation and analysis of E-fields of dual-site tACS at various phase-lag values.

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Abstract:tACS is a non-invasive stimulation technique where oscillating currents are applied to externally modulate cortical excitability and connectivity in the brain. While tACS seems to have promising results in altering oscillatory activity, there is a high variability of results between studies and subjects. There is a need for understanding the physiological mechanisms behind tACS. This study investigated changes in the tACS-induced electric field as a result of changing the size of stimulation ring electrodes and changing the phase-lag value between two cortices. A standard SimNIBS pipeline was used for finite element methods calculations, using Dirichlet and Neumann boundaries. A quasi-static regime is assumed. In this study, we have found more information on how the electric field induced by tACS responds to different settings of stimulation. Firstly, the sizes of the center-surround ring electrodes were changed and simulated. A compromise for a high focality and high strength of the electric field was found in the ring electrode montage where (Dcircle, Dinner−ring, Douter−ring) = (25, 78, 100) mm. Next, the effect of a phase-lag value between the cortices was simulated for values of φ = 0, φ = π, φ = 1/2π, and φ = 3/2π. The strength of the induced electric field is dependent on the tACS current that is applied through the electrodes. Changes in the electric field distribution compared to the φ = 0 stimulation, led to differences located below the stimulation electrodes. When the currents are of opposite polarity, there is also a difference present at the great longitudinal fissure. The direction of the electric field gradually changed from perpendicular to the cortex to a more parallel orientation to the cortex for all phase-lag simulations. While we gained new insights, the results are limited by their generalizability. With more research, the generalizability of the results could be expanded and new insights could be made.
Item Type:Essay (Bachelor)
Faculty:TNW: Science and Technology
Subject:02 science and culture in general, 42 biology, 44 medicine
Programme:Biomedical Technology BSc (56226)
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