Effects of High Amplitude and Focused tACS on Entraining Physiological Tremor

KU Leuven23 enrolled

Overview

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.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

SINGLE

Enrollment

Conditions

Tremor, Limb

Interventions

Outcomes

Primary Outcomes

Tremor-stimulation phase entrainment

phase locking value was calculated between the tremor signal measured using accelerometer and the stimulation signal

Time frame: During the 36 minutes of all sessions (3 sessions each of is 12 minutes)

Secondary Outcomes

Phosphene rating

The subject is asked to rate the phosphene intensity during the stimulation using a visual analog scale from 0 to 10. Zero means no phosphene is perceived and the number starts to increase as the phosphene perception intensity increases to reach 10 if the subject observe only a white view

Time frame: Measured up to 5 minutes before the start of the stimulation sessions and lasts for 10 seconds of stimulation after which the subject gives the rating

Phosphene threshold

Stimulation amplitude at which the subject starts to perceive phosphene. Stimulation starts with 0 mA amplitude and then increased gradually until phosphene is perceived (or reaching maximum amplitude).

Time frame: Measured 3 minutes before the start of the stimulation sessions and lasts up to 2 minutes. Stimulation at each amplitude lasts for 10 sec.