a-tDCS on the ipsilesional parietal cortex boosts the effects of prism adaptation treatment in neglect

Abstract

Background and objective: The aim of the study is to compare the effects of multiple sessions of cathodal (c-tDCS) or anodal tDCS (a-tDCS) in modulating the beneficial effects of prism adaptation (PA) treatment in neglect patients.

Methods: 30 neglect patients were submitted to 10 daily sessions of PA treatment. Patients were pseudo-randomly divided into 3 groups. In the c-tDCS-group, each PA session was coupled with 20 minutes of cathodal stimulation of the left, intact PPC; in the a-tDCS-group, anodal stimulation was applied to PPC of the damaged hemisphere; in the Sham group, sham stimulation was applied. Neglect was evaluated before and after treatment with the Behavioral Inattention Test.

Results: Combined tDCS-PA treatment induced stronger neglect improvement in the a-tDCSgroup as compared to the Sham group. No improvement was found in the c-tDCS group, with respect to that normally induced by PA and found in the Sham group.

Conclusions: c-tDCS abolished neglect amelioration after PA, possibly because stimulation affected the sensorimotor network controlling prism adaptation. Instead, a-tDCS PPC boosted neglect amelioration after PA probably thanks to increased excitability of residual tissue in the lesioned hemisphere, which in turn might reduce dysfunctional over-excitability of the intact hemisphere.

Keywords: Neglect; Prism Adaptation; tDCS.