Effects of tDCS in modulating the after-effect of prismatic lenses training in stroke patients with neglect

Abstract

Neglect treatment with prismatic lenses (PL) has been demonstrated to be effective in improving hemispatial neglect. This study aimed to compare the effect of cathodal transcranial direct current stimulation (c-tDCS), anodal tDCS (a-tDCS) or sham stimulation in modulating the PL effect in stroke patients. Fifteen subacute stroke patients with pathological performance on the Behavioral Inattention Test (BIT) battery, indicative of neglect, were included in this study. Patients underwent to a-tDCS over the right posterior parietal cortex (PPC), c-tDCS over the left PPC and sham stimulation during three PL training sessions (with PL of 10? rightward shift), in random sequence and separated by at least 1 day. Thirty “invisible” pointing (visual target not visible) were performed before and after each session to evaluate the after-effect of the PL training. Leftward shift after PL training was significantly reduced by a-tDCS over the ipsilasional PPC in comparison with c-tDCS over the contralesional PPC (p = 0.019) and sham stimulation (p = 0.047). No difference in the after-effect was obtained comparing the c-tDCS and sham stimulation. Error correction during the PL training do not significantly differed among the three sessions. A-tDCS over the ipsilesional PPC reduced the leftward deviation possibly interfering with the network involved in visuo-motor adaptation to PL training.