So, using tDCS, McKinley’s lab kept 30 people up for 30 hours to see how they fared with and without fatigue interventions. Essentially, they compared the effects of 200 mg of caffeine (about equal to 2 cups of coffee) to 30 minutes of tDCS at two milliamps (mA) applied to an area of the brain called the dorsolateral pre-frontal cortex, which is very important for the cognitive processes of attention and vigilance. The results suggest that applying electricity to a brain for half an hour is more effective than consuming something caffeinated.
Specifically, the people who were electrically stimulated were more vigilant for longer than those given caffeine — up to six hours versus two. Previous studies found that a shorter duration of tDCS could modulate vigilance for 30 to 90 minutes, which is within the range of the two hours of caffeine action. This time, said McKinley with excitement, “we recorded 6 hours after we gave the stimulation. This time it was 30 minutes of stimulation, and we did not see the performance taper off… there’s got to be a point where it drops off again, we just haven’t reached that… We were very surprised that 6 hours later it was still working… exciting, but also a little baffling.”