Guiding the Future of Brain Stimulation

Transcranial electrical stimulation techniques are widely used to regulate brain function and behavior. However, due to low reproducibility of various studies, the efficacy of this technique started to be questioned. This led researchers of the Decision Neuroscience Lab from the Department of Health Sciences and Technology at ETH Zurich to provide a guide for scientists to make informed decisions whether these technologies can be used to safely study brain functions.

Brain modulation techniques involving the application of weak electrical currents over the scalp are globally labelled transcranial electric stimulation (tES) and include transcranial direct current stimulation (dTCS), transcranial alternate current stimulation (tACS), and transcranial magnetic stimulation (TMS). In the last two decades, its use has sharply increased. Two decisive drivers of that trend are certainly that the portable technology is relatively cheap and easy to apply.
However, before tES can be established as a tool to study the causal role of neural oscillations in humans, we advocate for integrative studies, that combine knowledge generated across species, from rodents, monkeys and humans. We also need studies that compare systematically the impact of tES under variable behavioral states, e.g. ex-vivo, in-vivo, anesthetized or awake, and incorporate computational modeling that predict the impact and efficacy of tES. .

With our article, we provide a guide for planning and interpreting results of translational research based on non-invasive neuromodulatory technologies. First, we show that it is essential to match the strength of the stimulation methods across species by means of computational models. Second, we show how brain targets of these interventions may affect whole functional networks, and not just the targeted brain structure. Finally, when applying tES  in humans, one should consider variable brain anatomy of each person by using individualized head models.
We hope that knowledge gained from experiments conducted under our proposed integrative approach will allow improving and optimizing the impact of non-invasive brain stimulation in both, health and disease on individual basis. We believe that these integrative efforts are vital for successful applications of these treatments to improve mental health, thus offering an alternative when pharmacological interventions or other more risky and invasive treatments fail.

By: Valeriia Beliaeva & Rafael Polania, Department of Health Sciences and Technology, ETH Zurich, Decision Neuroscience Lab

Reference: Beliaeva, V., Savvateev, I., Zerbi, V. et al. Toward integrative approaches to study the causal role of neural oscillations via transcranial electrical stimulation. Nat Commun 12, 2243 (2021).

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