Anodal tDCS augments and preserves working memory beyond time-on-task deficits

Area of Science:

• Neuroscience
• Cognitive Psychology
• Human-Computer Interaction

Background:

• Transcranial direct current stimulation (tDCS) shows potential for enhancing working memory (WM).
• The efficacy of tDCS in mitigating cognitive fatigue and performance decline during sustained tasks remains unclear.
• Left dorsolateral prefrontal cortex (DLPFC) stimulation is a key area of interest for cognitive enhancement.

Purpose of the Study:

• To investigate the impact of anodal tDCS on the left DLPFC during a fatiguing visuospatial WM task.
• To assess tDCS effects on performance, subjective fatigue, and physiological markers like heart rate variability (HRV).
• To determine if tDCS can counteract time-on-task-related performance decrements.

Main Methods:

• A repeated measures design with 32 healthy adults undergoing anodal, control, and sham tDCS on separate days.
• Participants completed a 1-hour visuospatial two-back task with tDCS applied at 1 mA for 10 minutes, starting 20 minutes into the task.
• Measurements included task performance, subjective effort/fatigue ratings, and HRV.

Main Results:

• Anodal tDCS significantly improved WM performance compared to sham and control conditions in both sexes.
• These WM enhancements persisted beyond the stimulation period and were specific to performance measures.
• No significant differences in subjective effort or fatigue were observed, though discomfort was higher during stimulation.
• HRV increased under anodal tDCS and control conditions, while it plateaued under sham tDCS.

Conclusions:

• Short-duration anodal tDCS of the left DLPFC effectively counters time-on-task deficits in visuospatial WM tasks.
• tDCS enhances and preserves WM capacity, although these benefits are not perceived subjectively.
• Further research is needed to understand the practical application and operationalization of tDCS in human-centered systems.