Can transcranial electric stimulation with multiple electrodes reach deep targets?

Abstract

To reach a deep target in the brain with transcranial electric stimulation (TES), currents have to pass also through the cortical surface. Thus, it is generally thought that TES cannot achieve focal deep brain stimulation. Recent efforts with interfering waveforms and pulsed stimulation have argued that one can achieve deeper or more intense stimulation in the brain. Here we argue that conventional transcranial stimulation with multiple current sources is just as effective as these new approaches. The conventional multi-electrode approach can be numerically optimized to maximize intensity or focality at a desired target location. Using such optimal electrode configurations we find in a detailed and realistic head model that deep targets may in fact be strongly stimulated, with cerebro-spinal fluid guiding currents deep into the brain.\n\nO_LSTHighlightsC_LSTO_LIDeep targets can be reached with intensities comparable to the cortical surface.\nC_LIO_LIMulti-electrode montages increase intensity with the same current limits per electrode.\nC_LIO_LIHigh-definition and intersectional pulsed stimulation are largely equivalent.\nC_LIO_LIInterferential stimulation is generally weaker than conventional stimulation.\nC_LI