Modulation of human visuospatial attention analysis by transcranial direct current stimulation (tDCS) in the line bisection performance

The general population shows physiologic biases in the line bisection performance for visuospatial attention, almost to the left known as pseudoneglect. Previous studies have shown that tDCS affects visuospatial attention in line bisection. This research applies tDCS over left posterior parietal cortice (P3) or right posterior parietal cortice (P4) to explore the effect on pseudoneglect. Subjects randomly were divided into five groups by stimulation distribution: (i) P3-anodal (P3A), (ii) P3-cathodal (P3C), (iii) P4-anodal (P4A), (iv) P4-cathodal (P4C), (v) sham. Participants respectively finished the post-tDCS line-bisection assignment (lines on the left/right side of the monitor (LL/LR), and lines in the center of the monitor (LC)) the same as the pre-tDCS task over the session (P3A, P3C, P4A, P4C and sham) tDCS condition. The principal findings were that P3A tDCS reduced the leftward shift in the horizontal line bisection task, as well as P4C tDCS reduced the leftward shift in LL. Sham stimulation as well as P3C and P4A stimulation didn’t have systematic improvements in the line bisection tasks. Therefore, an activation–orientation model of pseudoneglect is corroborated by these findings. Activation of intact structures in the rebalance of left and right parietal cortex might impose modulating effects on tDCS.