A pilot study on effects of 4×1 high-definition tDCS on motor cortex excitability.
High-Definition transcranial Direct Current Stimulation (HD-tDCS) using specialized small electrodes has been proposed as a focal, non-invasive neuromodulatory technique. Here we provide the first evidence of a change in cortical excitability after HD-tDCS of the motor cortex, using TMS motor evoked potential (MEP) as the measure of excitability. Stimulation for 20 minutes at 1 mA with an anode centered over the hand area of the motor cortex and four surrounding return electrodes (anodal 4×1 montage) produced a significant increase in MEP amplitude and variability after stimulation, compared to sham stimulation. Stimulation was well tolerated by all subjects with adverse effects limited to transient sensation under the electrodes. A high-resolution computational model confirmed predictions of increased focality using the 4×1 HD tDCS montage compared to conventional tDCS. Simulations also indicated that variability in placement of the center electrode relative to the location of the target (central sulcus) could account for increasing variability. These results provide support for the careful use of this technique where focal tDCS is desired.
Departmento de Ciencias Fisiologicas, Universidade do Estado do Rio de Janeiro, UERJ. Av. Professor Manuel de Abreu 444, Pavilhao Americo Piquet Carneiro, 5 andar Vila Isabel, Rio de Janeiro, RJ, CEP: 20550-170.
Egas M
EM
Caparelli-Daquer
Trelawny J
TJ
Zimmermann
Eric
E
Mooshagian
Lucas C
LC
Parra
Justin K
JK
Rice
Abhishek
A
Datta
Marom
M
Bikson
Eric M
EM
Wassermann
D000328:Adult; D003198:Computer Simulation; D046690:Deep Brain Stimulation / Q000379:methods*; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008959:Models, Neurological; D009044:Motor Cortex / Q000033:anatomy & histology / Q000502:physiology*; D010865:Pilot Projects; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D055815:Young Adult