What Effect Does tDCS Have on the Brain? Basic Physiology of tDCS.

Purpose of the Review Transcranial direct current stimulation (tDCS) can effectively modulate a wide range of clinical and cognitive outcomes by modulating cortical excitability. Here, we summarize the main findings from both animal and human neurophysiology literature, which have revealed mechanistic evidence for the acute and neuroplastic after-effects of tDCS. Recent Findings Insights into the magnitude and geometric orientation of transcranially induced currents have been pro- vided by the combination of computational modeling of cur- rent flow in animal slice preparations and intracranial record- ings in humans. In addition to its synaptic effects, stimulation also induces after-effects on the glial and vascular systems, the latter also observed in humans by magnetic resonance imag- ing. Several studies have also observed non-linear or antago- nistic effects of tDCS parameters, which warrants further sys- tematic studies to explore and understand the basic mechanisms.

Summary tDCS is a valuable and promising technique across the neurophysiological, cognitive neuroscience, and clinical domains of research. Primary and secondary effects of tDCS still remain to be completely understood. An important chal- lenge for the field is advancing tDCS protocols forward for optimal intervention and treatment strategies.