OC20: Deep Intracerebral Electric Field Measurement with Stereoelectroencephalography during Transcranial Electrical Stimulations in Human in-vivo

Abstract

Measuring the electric field generated in several deep brain structures during Transcranial electrical stimulation in humans in-vivo. In addition, we investigated the effects of TES intensities and montages on the intracerebral EF. Transcranial electrical stimulation (TES) has shown for the last decades promises as a treatment for several neurological and psychiatric disorders. Its efficiency is related to the amount of electric field (EF) magnitude delivered on the target. Very few studies (n=3) estimated the in-vivo intracerebral electric fields in human. They relied mainly on electrocorticographic recordings that require a craniotomy and did not precisely focus on targeting the deep cortical structures which can still lead to some discussion about the TES possibility to reach deep structures. We applied Transcranial alternating current stimulations simultaneously with intracerebral recordings (SEEG) in 7 drug-resistant epileptic patients. Two low intensities were used in 6 patients (0.5 and 1mA) and 15 different montages were used in 1 patient. We calculated the electric field by subtracting voltage measured on contiguous intracerebral contacts. We found EF magnitude up to 0.29, 0.38 and 0.54 V/m respectively in the amygdala, the hippocampus, and the cingulate gyrus. Among 91 montage combinations, the global EF difference in the brain was significant in 65% of cases. We also confirmed experimentally that EF magnitude is proportional to TES intensity. In conclusion, EF at a magnitude which can induces stochastic effects, is achievable in the deep brain structures using low intensities. EF is highly correlated to the stimulation intensity and depends on montages.