P152. Anodal tDCS to the left sensorimotor area induces a short-lasting increase of parieto-occipital alpha activity in Parkinson’s disease

Abstract

Anodal transcranial direct current stimulation (tDCS) to the sensorimotor area modulates cortical excitability and motor symptoms in Parkinson’s disease (PD). In this study, we aimed to explore the cortical activity modulation behind this effect. In this double-blind randomized sham-controlled combined EEG and tDCS study, we studied nine idiopathic Parkinson’s disease patients after overnight withdrawal of dopaminergic medications. Patients were studied and crossed-over in two sessions on different days with either ‘verum’ or ‘sham’ stimulation on 20 min of anodal tDCS at 1 mA (electrodes placed over left ‘C3’ and right ‘Fp2’). EEG was registered simultaneously to tDCS. Cortical activity was expressed as frequency domain spectrum (power) and a topographic distribution was obtained from 25 cortical EEG channels. Data were masked for artifacts and segmented to consecutive epochs of 5 min, respectively (blocks 1–4). PD patients with ‘verum’ stimulation showed a strong initial increase of left parietal and bilateral occipital alpha oscillations centered at 9 Hz in block 1. In blocks 2–4 the initial alpha peak decreased and did not differ between ‘verum’ and ‘sham’ conditions at the end of the tDCS session. Anodal tDCS applied to the left sensorimotor region induces alpha activity synchronization in PD. Compensatory cortical mechanism might reverse this effect over time.