Document Type : Full Research Paper


1 Biomedical engineering group, Department of electrical and computer engineering, Tarbiat Modares University, Tehran, Iran

2 Tarbiat Modares University Department of electrical and computer engineering

3 Telecommunication group, Department of electrical and computer engineering, Tarbiat Modares University, Tehran, Iran



Working memory (WM) is an important cognitive function. Since WM capacity is limited, extensive research has been executed to improve it. Previous studies demonstrated that applying transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) enhances visual WM. Capacity enhancement of WM has a significant effect on the pilot's efficiency. However, little is known about the auditory-verbal WM of Pilots. Therefore, the aim of this study is to evaluate the effects of tDCS over the left DLPFC on the WM capacity augmentation of pilots. The auditory-verbal WM stimuli comprise characters that are random numbers and alphabet letters. The stimulus is presented through the pilot's headset, and he has been persuaded to memorize the auditory stimulus and repeat the memorized characters. The auditory task is a set of 30 voices and is designed in 6 stages. The task starts from the easiest stage (4 characters) and continues with 2 increments of characters per stage to the most difficult stage (14 characters). The experiment was conducted under three conditions: baseline, sham, and anodal-tDCS. Before running the task, 2mA electrical stimulation with a duration of 30 seconds for the sham and 10 minutes for the anodal-tDCS conditions, was applied over the left DLPFC region of pilots. The performance measure is the number of correct remembered characters. Statistical hypotheses showed significant effects of anodal-tDCS in comparison to baseline condition as follows: %6.41 WM enhancement by considering all stages; and also improved performance around %12.20 in stage 4, %9.00 in stage 5, and %10.44 in stage 6 which are the most difficult stages. As a result, we found that 2mA anodal-tDCS over the left DLPFC can modulate WM capacity. The current study can be utilized to discover evidence of cognitive, behavioral, or neural mechanisms of WM and its application for human augmentation.


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