The positive effects of tDCS on sustained attention performance under sleep deprivation conditions are consistent and repeatable

Abstract

Cognitive performance decrements resulting from sleep deprivation are well-documented and sources of human error for many occupations such as transportation, medicine, and the military. Sustained attention or vigilance is one of those cognitive skills that rapidly declines as fatigue increases. One potentially promising fatigue countermeasure is transcranial direct current stimulation (tDCS), a form of non-invasive brain stimulation. Previous studies show positive benefits of tDCS for fatigue, the question of how repeatable and reliable such findings are has been somewhat unclear. Utilizing data from two of our own laboratory studies that used the Mackworth Clock Test vigilance task, we examined the across-study repeatability and the reliability of using tDCS as a fatigue countermeasure. Both studies had the same experimental design of 3 groups, each group with an n-size of 10-12 participants. Group 1 received 30 minutes of anodal left dorsolateral prefrontal cortex stimulation (lDLPFC) at 1800 hours, Group 2 received 30 minutes of anodal lDLPFC at 0400 hours, and Group 3 received sham stimulation at 1800 and 0400 hours. The reference electrode was placed on the contralateral upper bicep. The ANOVAs show no statistical difference in performance between the same groups for the two studies. Correlations indicate that the comparisons between these two studies for the same groups are high (1800 stim r=0.91, 0400 stim r=0.94, sham r=0.94). These results, across two studies with similar structure but different participants, provides compelling evidence that the positive effects of tDCS on attentional decrements due to sleep deprivation stress are indeed reliable and repeatable. We have found in both studies that when compared to sham, tDCS can provide up to 6 hours of attentional performance enhancement after a single 30-minute session of tDCS regardless of when the stimulation is administered. Therefore, tDCS can be a powerful fatigue countermeasure for combating performance-related attentional deficits.