In Vivo Measurements of Cranial Electrical Stimulation Using Stereotactic-EEG: A Pilot Study

Cranial Electrical Stimulation (CES) is a promising non-invasive brain modulation technique in clinical application. However, whether CES could provide sufficient intracerebral currents and influence neural activity remains controversial because of the lack of direct in vivo evidence for CES-induced electric field distribution. In this pilot study, we directly measured CES-induced voltage distribution in two epilepsy participants undergoing presurgical evaluation with stereotactic-electroencephalographic (sEEG). An alternating sinusoidal current of 0.005 to 0.5 mA, 0.5 to 200 Hz was applied. We found that the measured voltages induced by CES increased their magnitudes with the stimulation intensity linearly in all electrodes. The magnitudes of measured voltages changed only a little when the CES stimulation frequency increased from 0.5 to 200 Hz. Combing with numerical simulations based on individual MRI, we further observed that both measured voltages and electric fields obtained in vivo are highly correlated with the predicted ones. The preliminary result from this in vivo study suggested that the CES stimulation could induce the electric field changes in the deep brain.