Transcranial electric stimulation (tES) and NeuroImaging: the state-of-the-art, new insights and prospects in basic and clinical neuroscience

Abstract

Transcranial electric stimulation (tES) of the brain has attracted an increased interest in recent years. Yet, despite remarkable research efforts to date, the underlying neurobiological mechanisms of tES' effects are still incompletely understood. This Special Issue aims to provide a comprehensive and up-to-date overview of the state-of-the-art in studies combining tES and neuroimaging, while introducing most recent insights and outlining future prospects related to this new and rapidly growing field. The findings reported here combine methodological advancements with insights into the underlying mechanisms of tES itself. At the same time, they also point to the many caveats and specific challenges associated with such studies, which can arise from both technical and biological sources. Besides promising to advance basic neuroscience, combined tES and neuroimaging studies may also substantially change previous conceptions about the methods of action of electric or magnetic stimulation on the brain.

A Review of Acute Aerobic Exercise and Transcranial Direct Current Stimulation Effects on Cognitive Functions and Their Potential Synergies

“…Moreover, it might worth considering that modulations in brain oscillatory activity such as in the individual alpha band (e.g., FAA) can be provoked by exercise and tDCS and tACS (Zaehle et al, 2010, 2011b; Herrmann et al, 2013; Soekadar et al, 2016; Herrmann and Strüber, 2017; Kasten and Herrmann, 2017). Because several neurological and psychiatric conditions are associated with dysfunctional brain synchronization and maladjusted oscillatory communication (Stam et al, 2003; Schnitzler and Gross, 2005), a combined application of AE and tACS/tDCS could help research to modulate brain oscillations and study the associated behavior systematically.…”

Modulating Applied Task Performance via Transcranial Electrical Stimulation

“…We point to three primary challenges in considering tES for application to applied contexts and tasks. First, safe and effective tES administration relies on a highly complex and underspecified parameter space (Soekadar et al, 2016). These include variation in targeted brain regions, electrode positioning and sizing, stimulation intensity, timing and duration, and the polarity (anodal, cathodal) of tDCS and frequency of tACS.…”

“…Similar influences of individual differences in predicting tES influences have been found in several recent studies: high creative potential is linked to increased breadth of semantic associations with left frontopolar tDCS (Brunyé et al, 2015), working memory capacity and educational level are linked to increased neural activity and cognitive function with left DLPFC tDCS (Berryhill and Jones, 2012; Jones et al, 2015), and trait mathematics anxiety is linked to whether left DLPFC tDCS improves arithmetic task performance (Sarkar et al, 2014). Continuing research will likely find additional predictive value in trait-based measures, and the field will continue to benefit from neuroimaging in at least three ways: individualized targeting of brain regions (Bikson et al, 2012), closed-loop stimulation triggering using structural and functional brain imaging (McKendrick et al, 2015), and improved mechanistic understandings of tES effects at the level of neurons, neural networks, and behavior (Filmer et al, 2014; Soekadar et al, 2016).…”

Oscillating neural networks: perspectives from rhythmic brain stimulation

“…In the following chapter (Chapter 2), I avoided this issue by conducting two related experiments: the first with only EEG (establishing a paradigm that engages a network of coherent oscillations), and the second with only rhythmic brain stimulation (targeting the established network with HD-tACS but assessing only the behavioural outcomes). Given its scientific value Soekadar et al, 2016), a major interest of mine is concurrent M/EEG-tACS (see These are discussed in the context of what could be considered crises in the field: reproducibility and sample size (Veniero et al, 2015), low field intensities , and the contribution of false positives to electrophysiological evidence of entrainment (Noury et al, 2016).…”

“…Pairing techniques of non-invasive brain stimulation with neuroimaging has great scientific value Soekadar et al, 2016), but the recovery of this information during stimulation ("online") can be very challenging. Techniques of rhythmic stimulation may entrain neural oscillations in a frequency-specific manner (Veniero et al, 2015), but they also contaminate the magneto-and electro-encephalogram (M/EEG) with large artefacts that can complicate spectral analyses.…”