Animal studies in the field of transcranial electric stimulation

Abstract

Dozens of animal studies of transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS) have provided insight into the cellular mechanism of stimulation. Biomarkers of tDCS/ tACS responses at the neurophysiological, behavioral, and molecular levels provide a basis to design clinical interventions that engage specific targets. This chapter provides a broad introduction to methods and insights from animal models. Both tDCS and tACS are sub-threshold techniques, producing membrane polarization rather than firing. If the nervous system is engaged during tDCS/tACS, for example by cognitive behavioral therapy, then tDCS/tACS modulate this ongoing activity. Animal models have supported the basis for polarity-specific effects of tDCS ("anodal" excitation, "cathodal" inhibition) while also indicating limitations of simplistic dose strategies. tACS studies have focused on boosting of oscillations. Both techniques can modulate ongoing plasticity leading to lasting changes in brain function. As an adjunct therapy, tDCS/tACS may thus increase brain capacity for plasticity enhancing the effects of neuropsychiatric therapies, and compensating for disease-related decline.