Abstract
Transcranial direct current stimulation (tDCS) of the left dorsolateral prefrontal cortex (DLPFC) has been shown to promote working memory (WM), however, its efficacy against time-on-task-related performance decline and associated cognitive fatigue remains uncertain. This study examined the impact of anodal tDCS of the left DLPFC on performance during a fatiguing visuospatial WM test. We adopted a repeated measures design, where 32 healthy adults (16 female), underwent anodal, control and sham tDCS on separate days. They completed an hour long two-back test, with stimulation intensity, onset, and duration set at 1 mA, at the 20th minute for 10 minutes respectively. Task performance, subjective responses, and heart rate variability (HRV) were captured during the experiment. Anodal tDCS substantially improved WM relative to sham tDCS and control in both sexes. These benefits lasted beyond the stimulation interval, and were unique across performance measures. However, no perceptual changes in subjective effort or fatigue levels were noted between conditions, although participants reported greater discomfort during stimulation. While mood and sleepiness changed with time-on-task, reflecting fatigue, these were largely similar across conditions. HRV increased under anodal tDCS and control, and plateaued under sham tDCS. We found that short duration anodal tDCS at 1 mA was an effective countermeasure to time-on-task deficits during a visuospatial two-back task, with enhancement and preservation of WM capacity. However, these improvements were not available at a perceptual level. Therefore, wider investigations are necessary to determine “how” such solutions will be operationalized in the field, especially within human-centered systems.
Highlights
Transcranial direct current stimulation of the left dorsolateral prefrontal cortex (DLPFC) has been shown to promote working memory (WM), its efficacy against time-on-task-related performance decline and associated cognitive fatigue remains uncertain
Neuroimaging studies have shown that Brodmann areas 46 and 9, i.e. primarily the left dorsolateral prefrontal cortex (DLPFC)[6], are most associated with WM and related executive function, and this region has been a focal point for targeted neuromodulation[7]
We explored the role of Transcranial direct current stimulation (tDCS) on sustained attention during a prolonged (60 minute) psychomotor vigilance test (PVT)[18], where we relied on the PVT to serve both as a fatigue induction paradigm and as a measure of attention capacity—informed by related efforts that consider the influence of timeon-task and its impact on sustained attention[19]
Summary
Transcranial direct current stimulation (tDCS) of the left dorsolateral prefrontal cortex (DLPFC) has been shown to promote working memory (WM), its efficacy against time-on-task-related performance decline and associated cognitive fatigue remains uncertain. In examining the efficacy of tDCS as a fatigue countermeasure, McIntire et al.[16] demonstrated that anodal tDCS for 30 min at 2 mA resulted in improvements on attentional accuracy during vigilance tasks beyond the effects of sleep deprivation. They found no direct effect of stimulation on WM during those experiments. Research that evaluates the effectiveness of dosage, timing, and duration in task contexts beyond those previously tested is needed, as these factors drive subsequent use and acceptance in time-sensitive field applications such as ER
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
