PB 20 Anodal tDCS over the left sensorimotor area improves motor function and suppresses cortical beta activity in Parkinson’s disease

Abstract

Motor network activity in the beta range is correlated with motor symptoms in Parkinson’s disease (PD). Anodal tDCS over the sensorimotor area modulates cortical excitability and may alleviate motor symptoms in PD. In this study, we aimed to explore the effect of anodal transcranial direct current stimulation over the left sensorimotor area on clinical motor outcome, right hand fine motor performance and cortical motor network activity. In this double-blind randomized sham-controlled combined EEG and tDCS study, we investigated ten pharmacologically treated idiopathic PD patients after overnight withdrawal of dopaminergic medication and eleven healthy controls during an isometric precision grip task before and after stimulation. Participants were studied and crossed-over in two sessions on different days with either “verum” or “sham” stimulation of anodal tDCS (20 min; 1 mA; electrodes placed over left ‘C3’ (anode) and right ‘Fp2’ (cathode)). Cortical activity was expressed as frequency domain spectrum (power) and the topographic distribution was obtained from 25 cortical EEG channels placed according to the 10–20 system. Fine motor performance was expressed as accuracy error during the precision grip task with lower accuracy error indicating higher motor precision. Clinical motor outcome was measured using the UPDRS III motor score. PD patients with “verum” stimulation showed a significant decrease of beta power over the left primary motor area (electrode position ‘C3’) centered from 22 to 27 Hz and a significant decrease in the UPDRS III motor score. Both changes were most pronounced directly after stimulation and lasted for at least 30 min. These effects were specific for the PD “verum” condition and absent in both PD “sham” and in healthy controls “verum” and “sham” conditions. Both groups showed no significant change regarding the accuracy error after stimulation. Anodal tDCS applied to the left sensorimotor area induces beta power decrease over the left primary motor area and clinical motor improvement in PD.