Effects of High Amplitude and Focused tACS on Entraining Physiological Tremor

Transcranial alternating current stimulation (tACS) is a noninvasive neuromodulation method that works by passing alternating electric current between electrodes where at least one of them is attached to the head. While tACS applied over the motor cortex at the general applied amplitude (1 mA) and using patch electrodes has been shown to entrain physiological tremor in healthy volunteers, the aim of this study is to test the feasibility of using high-amplitude tACS and to assess the effect of different electrode montages and stimulation sites in entraining physiological tremor. First, 10 subjects (arm 1) will be stimulated with 2 mA current amplitude applied between saline soaked patch square electrodes and comparison will be done between motor cortex stimulation and peripheral cortex stimulation. Then, 10 subjects (arm 2) will be stimulated using focused 4x1 montage with gel-filled cup-electrodes and 5 mA amplitude and comparison will be made between motor cortex and occipital cortex stimulation. Three outcome measurements will be measured during the experiments which are: tremor entrainment, phosphene intensity and phosphene threshold.