Conventional or High Definition tDCS to Enhance Implicit Motor Sequence Learning in Healthy Young Adults?

"tDCS will be delivered through a pair of identical square rubber electrodes (size 35 cm2), placed in rectangular saline-soaked sponges. For the stimulation of M1, electrodes will be placed over C3 or C4 according to the 10-20 EEG system, matching with the M1 contralateral to the performing dominant hand. The reference electrode will be positioned on F1 or F2, ipsilateral to the dominant hand.~The current stimulation will be slowly ramped up from 0 mA to 2 mA in one minute. For the anodal tDCS condition, this intensity will be maintained for the duration of the SRT-task (approximately 20 minutes). This will result in a current density of 0,057 mA/cm2. For the sham tDCS condition - unbeknown to the subject - stimulation will be gradually decreased towards 0 mA immediately after the one-minute ramp-up. During the last block of the SRT-task, this gradual ramping-up and -down of the current stimulation will be repeated to optimize the process of blinding of participants."

"HD tDCS will be delivered over M1. By connecting the conventional tDCS device (described above) to this adapter, the direct current is delivered along the 4x1 HD tDCS configuration, allowing for more specific neuromodulation. Stimulation is delivered by means of one central gel-electrode and four return-electrodes placed in plastic encasings embedded in an EEG cap.~Stimulation of left M1 (right hand = performing): delivered via the central electrode corresponding with C3 and held in place using a synthetic cap to hold the HD-tDCS electrodes on the head. Return-electrodes are positioned at Cz, F3, T7 and P3 (10-20 EEG system).~Stimulation of right M1 (left hand = performing): central electrode will be positioned at C4 with the return-electrodes at Cz, F4, T8 and P4.~Strategies for anodal and sham stimulation are identical to the ones described above (conventional tDCS)."