Impact of Transcranial Direct Current Stimulation on Fatigability and Fatigue Induced by a Selective Attention Task

Right handed healthy individuals aged 18-40 will be eligible to participate. Participants will be randomized in a 1:1:1 ratio to receive real or placebo 2mA tDCS delivered for 20 minutes while performing a 3 hour computerized cued Stroop task. Groups will receive real or sham stimulation during the first 20 minutes or 90-110 minutes into the task. Groups will be: 1) Sham (sham given at both time points); 2) Prevent (real will be given during first 20 minutes to try to prevent or delay fatigue and sham given at second time point); or 3) Rescue (sham will be given initially and real given at 90-110 minutes to see if performance can be rescued after fatigue has set in). The primary outcome measure will be the slope of change for intra-individual variability of response time for correct items and regression models will be used to determine whether real preventative or rescue tDCS alters the rate of performance change relative to sham stimulation. Accuracy and mean response time will also be examined as secondary outcomes.