This research project is focusing on changes in mental fatigue due to transcranial direct current stimulation (tDCS) in healthy individuals. The study aim is to see if mental fatigue can be rescued by administering a safe dose of tDCS. tDCS has been shown to decrease fatigue in healthy individuals experiencing extended wakefulness, and the investigators aim to investigate if similar results can be found in a fatigue inducing task. This is a single-blind randomized control trial that will compare mental fatigue between tDCS treatment and sham treatment groups through both subjective and objective measures. Objective fatigue will be measured by reaction time with the Stroop test and subjective fatigue will be measured by the multidimensional fatigue inventory questionnaire.
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.
Inclusion Criteria:
Exclusion Criteria:
pregnant women,
history of medical conditions associated with fatigue, including, but not limited to: