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

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

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.

Subjects assigned to this arm will receive transcranial direct current stimulation (tDCS) that delivers a constant, small current (2 milliAmp) across specific regions of the brain through electrodes placed on the scalp half-way through the 3-hour fatigue task.

Subjects assigned to this arm will initially receive current of the same intensity for a period of 30 seconds and then gradually turned off.

Subjects assigned to this arm will receive transcranial direct current stimulation (tDCS) that delivers a constant, small current (2 milliAmp) across specific regions of the brain through electrodes placed on the scalp at the beginning of the task.

This will be measured by change in intraindividual variability of reaction time from the Stroop Fatigue Paradigm which will be quantified as the rate of change in mean reaction time over 3 hours modeled using linear regression.

This will be assessed by visual analogue scale of fatigue performed at baseline and every 30 minutes of the task and the slope of change in perceived fatigue modeled using linear regression.

Inclusion Criteria: right-handed normal or corrected-normal vision, Exclusion Criteria: pregnant women, history of medical conditions associated with fatigue, including, but not limited to: Parkinson's disease, Alzheimer's disease, diabetes mellitus, hypothyroidism, chronic fatigue syndrome, anemia, infectious mononucleosis, irritable bowel syndrome