Transcranial Current Brain Stimulation (tCS): Models and Technologies

Abstract

Abstract-In this paper, we provide a broad overview of models and technologies pertaining to transcranial current brain stimulation (tCS), a family of related noninvasive techniques including direct current (tDCS), alternating current (tACS), and random noise current stimulation (tRNS). These techniques are based on the delivery of weak currents through the scalp (with electrode current intensity to area ratios of about 0.3-5 A/m ) at low frequencies (typically 1kHz) resulting in weak electric fields in the brain (with amplitudes of about 0.2-2 V/m). Here we review the biophysics and simulation of noninvasive, current-controlled generation of electric fields in the human brain and the models for the interaction of these electric fields with neurons, including a survey of in vitro and in vivo related studies. Finally, we outline directions for future fundamental and technological research.Index Terms-Brain stimulation, electrical stimulation, transcranial alternating current (tACS), transcranial current stimulation (tCS), transcranial direct current (tDCS), transcranial random noise current stimulation (tRNS).

Measurements and models of electric fields in the in vivo human brain during transcranial electric stimulation

“…Transcranial electric stimulation (TES) delivers weak electric currents to the scalp with the goal of modulating endogenous brain activity (Ruffini et al, 2013). Stimulation can be applied as constant unidirectional current (tDCS) or biphasic alternating current (tACS).…”

An open letter concerning do‐it‐yourself users of transcranial direct current stimulation

“…Current flows between electrodes in complex ways based on different tissues in the head, and can affect the function of various structures along its path. 11–15 Furthermore, the effects of tDCS can extend beyond brain regions directly affected by the stimulation to connected brain regions and networks. 16–20 These indirect effects of stimulation on connected brain networks may alter brain functions that are unintended.…”

Effect of prefrontal and parietal tDCS on learning and recognition of verbal and non-verbal material

“…Both setups have been used successfully in memory studies (Fregni et al, 2005;Javadi and Cheng, 2013;Manenti et al, 2013). As a note of caution, it may be noted that in bilateral electrode montages with variable distance between the anode and the cathode, the current may not be distributed in an equal way in the two montages Ruffini et al, 2013). A direct current of 1 mA with a fade-in and fade-out of 8 s was delivered for 24 min for the anodal stimulation conditions.…”

“…While the electrode setup was standard, it is possible that this result was influenced by the distance between the electrodes, which was longer in the parietal stimulation group. The electrical field reaches its maximum intensity towards the middle between the two electrodes Ruffini et al, 2013) so that the stimulation presumably extends beyond the site under the anode. This caveat does not put into question the specificity of the effects observed with the two electrode setups in this study.…”

“…This caveat does not put into question the specificity of the effects observed with the two electrode setups in this study. High density electrode montages would allow for more focal stimulation effects in the future Ruffini et al, 2013).…”