Enhancement of Visuospatial Working Memory by Transcranial Direct Current Stimulation (tDCS) on Prefrontal and Parietal Cortices

Objective: Previous studies have reported dorsolateral prefrontal cortex (DLPFC) and posterior parietal (PPC) activation during the performance of spatial working memory (SWM), so we decided to investigate the comparison of Transcranial Direct current stimulation (tDCS) effect between these two areas. Methods: Fifty-four healthy right-handed students (27 female, 27 male; age= 24.3±.2 years) were randomly assigned to anodal (N=27) and sham group (N= 27), each of these groups was further divided into F4 (representing right DLPFC) or P4 (representing right PPC) subgroups, respectively. A Computerized Corsi Block Tapping task has then used to measure spatial working memory. The t-DCS intervention consisted of five daily sessions with a direct current of 1.5 mA for 15 minutes over the F4 or P4 area of the brain at 24-hour intervals. Results: Significant enhancement of the SWM span as well as a faster response were seen after anodal tDCS in both the forward and backward direction. Moreover, the left DLPFC stimulation induced a faster reaction time compared to the right PPC. Conclusions: Both DLPFC and PP cortices stimulation, as an element of the frontoparietal network, showed SWM enhancement, with the DLPFC being more effected. Our finding provides new evidence for the comparison of the effect of stimulation on the two main activated cortical areas during visuospatial WM.