Transcranial direct current stimulation: a roadmap for research, from mechanism of action to clinical implementation

Abstract

Transcranial direct current stimulation (tDCS) is a promising method for altering the function of neural systems, cognition, and behavior. Evidence is emerging that it can also influence psychiatric symptomatology, including major depression and schizophrenia. However, there are many open questions regarding how the method might have such an effect, and uncertainties surrounding its influence on neural activity, and human cognition and functioning. In the present critical review, we identify key priorities for future research into major depression and schizophrenia, including studies of the mechanism(s) of action of tDCS at the neuronal and systems levels, the establishment of the cognitive impact of tDCS, as well as investigations of the potential clinical efficacy of tDCS. We highlight areas of progress in each of these domains, including data which appears to favor an effect of tDCS on neural oscillations rather than spiking, and findings that tDCS administration to the prefrontal cortex during task training may be an effective way to enhance behavioral performance. Finally, we provide suggestions for further empirical study that will elucidate the impact of tDCS on brain and behavior, and may pave the way for efficacious clinical treatments for psychiatric disorders.

White matter hyperintensities affect transcranial electrical stimulation in the aging brain

“…Further, computed electric field strength within WMH regions had a maximum of 3.54 V/m which is smaller than the electric field needed to cause pyramidal neurons to fire (28e79 V/m) [25]. Therefore, stimulating brain regions with WMH presence should not induce an instant neuronal firing at the time of stimulation which agrees with previous tES literature [26]. However, the potential effects of current pooling within the lesion regions on neuronal firing warrant further research.…”

Group and Individual Level Variations between Symmetric and Asymmetric DLPFC Montages for tDCS over Large Scale Brain Network Nodes

“…EF calculations in the main nodes are depicted in Fig.7 and numerical results can be found in Table.S2 in supplementary materials. According to the brain's compensatory response to intervention through the neural networks, a simple hypothesis is that modulating multiple nodes of a network would be more effective than modulating a single node in that network [53]. As shown in Fig.7, the intensity of the induced EFs in distinct nodes of a network are different.…”

Efficacy of non-invasive brain stimulation on cognitive functioning in brain disorders: a meta-analysis

“…Until now, the efficacy of NIBS is unclear and some have questioned whether these techniques have any effect on the brain at all (Vöröslakos et al, 2018 ). Skepticism is increased by lack of clear theories and evidence on working mechanisms of both interventions, which hampers smart applications (Chase, Boudewyn, Carter, & Phillips, 2020 ; Singh, Erwin-Grabner, Goya-Maldonado, & Antal, 2019 ) Nevertheless, many studies have applied NIBS techniques in an attempt to improve cognitive function in different diagnostic groups. Although some studies showed promising findings, the results of studies on the effect of NIBS on cognition remain inconsistent and the field would benefit from an overarching systematic overview of findings so far.…”