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Session: Brain
Session starts: Friday 27 January, 14:00
Presentation starts: 15:15
Room: Room 558

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Silvana Huertas-Penen (Biomedical Signals and Systems, University of Twente)
Marieke Rona (University of Twente)
Tjitske Heida (Biomedical Signals and Systems, University of Twente)
Bettina C. Schwab (Biomedical Signals and Systems, University of Twente)

Abstract:
In the past years, transcranial alternating current stimulation (tACS) has been investigated as an intervention for different neurological conditions/diseases. There is high variability between tACS studies depending on the subjects and the settings of stimulation. This has no clear explanation, but understanding the physiological mechanisms behind the effects of tACS could help compensate for the variability. Analysing the variations in brain functional connectivity when changing the settings of dual-site tACS in the motor cortices, could help to identify the physiological mechanisms behind it as well as understanding the role of stimulation settings in steering the brain's functional connectivity. As a first step toward studying the functional connectivity of the brain in dual-site tACS, our research will determine which stimulation montage to use, including the positioning and size of electrodes to avoid spatial overlap of the electric fields of the motor cortex. The stimulation intensity used was 1.5 mV (zero-to-peak). This value was chosen because multiple studies have shown that to influence the brain, the intensity needs to be above 1mV. However, without local anaesthetics, participants feel high discomfort at intensities equal to or above 2mV. The criteria to select the position and size of electrodes were to maximize the field strength and focality of the electric field in the motor cortices. In addition, the field strength must be the same in both cortices. Finite element method (FEM) simulations were performed using SimNIBS. We simulated more than 20 different montages of stimulation electrodes (ring-electrodes, circular electrodes and pad electrodes) using the ICBM152 MRI head model template. We found that having 110/90 mm outside ring electrodes and 25 mm inside electrodes, located in the C3 and C4 EEG electrode positions, had the most favourable compromise between electric field intensity in the motor cortices and avoidance of spatial overlap of electric fields. With these results, the next steps are to experimentally stimulate participants while changing the settings of the stimulation between cortices. We will also generate computational neural network models based on the hypothesized physiological mechanisms of tACS and compare their results with the experimental ones.