Effects of transcranial direct current stimulation on resting state connectivity in mesial temporal lob epilepsy

The aim of this study is to explore the effect of transcranial direct current stimulation (tDCS) on resting state networks (RSN) in patients diagnosed as mesial temporal lobe epilepsy (MTLE) and tDCS' longterm effect on RSN in healthy controls. 17 drug resistance unoperated patients with left MTLE and 16 healthy controls were included in this study. fMRI was performed before and after cathodal (c) tDCS sessions. Single session of tDCS was applied in MTLE, while multiple sessions (3 consecutive days) of tDCS were applied in healthy controls. Increased FC following single session of c-tDCS was observed between the SN anterior cingulate and left temporal lobe, and between the left putamen and left opercular cortex, left Heschl's gyrus, whereas c-tDCS decreased the interhemispheric coherence of resting fMRG signal between the left orbitofrontal cortex and right lateral occipital cortex in left MTLE compared with healthy controls. Main effect of c-tDCS was increased FC between DMN and regions including SN, while it was decreased FC within DMN in MTLE and healthy controls. Effect of multiple session of c-tDCS showed that increased FC between the left anterior thalamus and left temporal was preserved after 7 days in healthy controls. Our previous study showed that seizure frequency significantly decreased after c-tDCS in MTLE. The present findings indicate neural underpinnings of c-tDCS' therapeutic effect. Multiple session of c-tDCS' effects were longterm on RSN in healthy controls. This finding may also shed light on the mechanism of decreased seizure frequence after tDCS in MTLE patients.