RT Journal Article SR Electronic T1 Spatiotemporal structure of intracranial electric fields induced by transcranial electric stimulation in human and nonhuman primates JF bioRxiv FD Cold Spring Harbor Laboratory SP 053892 DO 10.1101/053892 A1 Alexander Opitz A1 Arnaud Falchier A1 Chao-Gan Yan A1 Erin Yeagle A1 Gary Linn A1 Pierre Megevand A1 Axel Thielscher A1 Michael P. Milham A1 Ashesh Mehta A1 Charles Schroeder YR 2016 UL http://biorxiv.org/content/early/2016/05/18/053892.abstract AB Transcranial electric stimulation (TES) is an emerging technique, developed to non-invasively modulate brain function. However, the spatiotemporal distribution of the intracranial electric fields induced by TES remains poorly understood. In particular, it is unclear how much current actually reaches the brain, and how it distributes across the brain. Lack of this basic information precludes a firm mechanistic understanding of TES effects. In this study we directly measure the spatial and temporal characteristics of the electric field generated by TES using stereotactic EEG (s-EEG) electrode arrays implanted in cebus monkeys and surgical epilepsy patients. We found a small frequency dependent decrease (10%) in magnitudes of TES induced potentials and negligible phase shifts over space. Electric field strengths were strongest in superficial brain regions with maximum values of about 0.5 mV/mm. Our results provide crucial information for the interpretation of human TES studies and the optimization and design of TES stimulation protocols. In addition, our findings have broad implications concerning electric field propagation in non-invasive recording techniques such as EEG/MEG.