Transcranial Direct Current Stimulation (tDCS) is a safe, noninvasive technique that applies small amounts of current (1‐2 mA, 10‐30 minutes) through electrodes placed on the scalp. Over the past 15 years, a growing number of studies have shown that tDCS can selectively modulate cortical excitability in underlying brain regions in healthy and patient populations with measurable effects on various aspects of cognitive performance (e.g., working memory, attention, executive function, language, numerical competence) and potentially long‐lasting benefits.
During and immediately after application, anodal tDCS increases cortical excitability at the stimulation site through neuron soma depolarization, whereas cathodal tDCS decreases cortical excitability at the stimulation site due to neuron soma hyperpolarization. Long‐term effects may be due to neuroplasticity following LTP‐like changes in synaptic strength between stimulated neurons involved in task performance. A strength of the procedure relative to other brain stimulation techniques is its reliable sham manipulation, as there are no muscle twitches and it is silent, thus, it can be interrupted unbeknownst to participants. Critically, the low cost, ease of use, and safety of tDCS highlight its potential as a broad intervention for altering cognitive performance, with at‐home use devices already available.
On the other hand, recent quantitative reviews of the neurophysiological and cognitive literature raise serious questions regarding the effectiveness of tDCS to induce reliable neuroplastic changes that measurably affect cognition. Variability in the robustness of tDCS‐linked cognitive effects may largely be due to the small sample sizes, the scarcity of data on dose‐response effects, and substantial methodological variability across these studies. All of these limitations are exacerbated by a lack of knowledge on the precise mechanistic effects of tDCS on the brain over short‐ and long‐timeframes.
The aim of this Frontiers Research Topic is to assemble a collection of papers from experts in the field of non‐invasive brain stimulation that will discuss (1) the strength of the evidence regarding the potential of tDCS to modulate different aspects of cognition; (2) methodological caveats associated with the technique that may account for the variability in the reported findings; and (3) a set of challenges and future directions for the use of tDCS that can determine its potential as a reliable method for cognitive rehabilitation, maintenance, or enhancement.
Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.
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