Using high-amplitude and focused transcranial alternating current stimulation to entrain physiological tremor

Sci Rep. 2018 Mar 21;8(1):4927. doi: 10.1038/s41598-018-23290-w.

Abstract

Transcranial alternating current stimulation (tACS) is a noninvasive neuromodulation method that can entrain physiological tremor in healthy volunteers. We conducted two experiments to investigate the effectiveness of high-amplitude and focused tACS montages at entraining physiological tremor. Experiment 1 used saline-soaked sponge electrodes with an extra-cephalic return electrode and compared the effects of a motor (MC) and prefrontal cortex (PFC) electrode location. Average peak-amplitude was 1.925 mA. Experiment 2 used gel-filled cup-electrodes in a 4 × 1 focused montage and compared the effects of MC and occipital cortex (OC) tACS. Average peak-amplitude was 4.45 mA. Experiment 1 showed that unfocused MC and PFC tACS both produced phosphenes and significant phase entrainment. Experiment 2 showed that focused MC and OC tACS produced no phosphenes but only focused MC tACS caused significant phase entrainment. At the group level, tACS did not have a significant effect on tremor amplitude. However, with focused tACS there was a significant correlation between phase entrainment and tremor amplitude modulation: subjects with higher phase entrainment showed more tremor amplitude modulation. We conclude that: (1) focused montages allow for high-amplitude tACS without phosphenes and (2) high amplitude focused tACS can entrain physiological tremor.

Publication types

  • Clinical Trial
  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Female
  • Humans
  • Male
  • Motor Cortex / physiopathology*
  • Occipital Lobe / physiopathology*
  • Prefrontal Cortex / physiopathology*
  • Transcranial Direct Current Stimulation*
  • Tremor* / physiopathology
  • Tremor* / therapy