Experimental: Active tDCS

Based on previous studies targeting working memory, focality of current delivery, and comfort and tolerance levels, (Paulo S. Boggio et al., 2006; Hill et al., 2016; Hoy et al., 2013; Teo, Hoy, Daskalakis, \& Fitzgerald, 2011), we will use a 2 mA current administered via two circular carbon rubber core electrodes in saline-soaked surface sponges (25 cm2), placed in a neoprene headcap with marked locations based on the 10-10 EEG system. The anodal stimulating electrode will be at location F3, over left dorsolateral prefrontal cortex (DLPFC) and the cathodal electrode at location F4, over right DLPFC. Two reference electrodes, CMS and DRL, will be attached to the EarClip and applied to the earlobe with conductive gel.~Before each training session, the impedance of the electrodes will be checked and verified to be ≤15 KOhm. Additionally, the stimulation will be terminated if the impedance of the electrodes is \> 20 KOhm. The current and impedance will be recorded for every session.

Sham_comparator: Sham tDCS

For sham stimulation, the electrodes will be placed at the same positions as for active stimulation (F3 and F4). After an initial ramp-up period of 30 seconds, stimulation fades out over a period of 30 seconds. Additionally, at the end of the sham stimulation period, stimulation will fade in over a period of 30 seconds and then end with a final 30 second ramp-down period. Participants will feel the initial itching sensation associated with tDCS and experience the ramp-down period at the end of the sham stimulation period but will receive no active current during the rest of the sham stimulation period. This method of sham stimulation has been shown to be reliable (Gandiga et al., 2006).~Before each training session, the impedance of the electrodes will be checked and verified to be ≤15 KOhm. Additionally, the stimulation will be terminated if the impedance of the electrodes is \> 20 KOhm. The current and impedance will be recorded for every session.