P 192. Transcranial direct current stimulation modulates functional connectivity within and between motor cortices

Abstract

Introduction tDCS over the primary sensorimotor cortex (SM1) has been shown to induce changes in motor performance and learning. Recent studies indicate that tDCS is capable of modulating neural network properties within the whole brain. Objectives To investigate the temporal evolution of online tDCS effects on functional connectivity within and between the stimulated sensorimotor cortices. Materials and methods Two different tDCS montages were investigated: (i) unilateral tDCS (anode over right SM1, cathode over contralateral supraorbital region) and (ii) bilateral tDCS (anode over right and cathode over left SM1). In a randomized single-blinded crossover design, 12 healthy subjects underwent functional magnetic resonance imaging (fMRI) at rest before, during and after bilateral, unilateral or sham tDCS at rest. Seed-based analysis was used to investigate tDCS-induced changes in functional connectivity between SM1 and interconnected areas. Results Both uni-and bilateral tDCS, induced dynamic and non-linear changes in functional connectivity of both SM1 and interconnected brain areas. More specifically, tDCS induced decreases in functional connectivity between both SM1 as compared to sham in both conditions. This effect was more prominent during bilateral tDCS as compared to unilateral tDCS. Furthermore, only during bilateral tDCS, an increase in intracortical connectivity within right M1 was observed. Conclusion Our results provide evidence that depending on the electrode montage, tDCS acts upon a modulation of either intracortical and/or interhemispheric processing of SM1.