Psychobiological Responses Following Exercise and Brain Stimulation

Transcranial direct current stimulation (tDCS), a non-invasive central neuromodulatory technique that is inexpensive and safe, has been utilized to stimulate specific regions of the brain and has demonstrated promising results for alleviating anxiety and depression. (1) evidence supports the administration of anodal stimulation over the left dorsolateral prefrontal cortex (DLPFC) to excite neuronal activity and cathodal stimulation over the right DLPFC to inhibit activity (a bicephalic tDCS montage with 2 mA of stimulation at the left DLPFC) as the most effective tDCS treatment to alleviate anxiety in humans and (2) that "tDCS may be more effective when used in combination with drugs and cognitive behavioral therapies". However, results from studies that have examined the neurophysiological and behavioral effects of tDCS are not consistent. This is likely because the highest cortical current density may not have occurred directly under the target electrode, thus altering the effects of tDCS. High-density tDCS (HD-tDCS) is similar to conventional tDCS utilizing anode and cathode placement on the scalp to produce unidirectional current flow, however, to enhance precision and accuracy, HD-tDCS utilizes smaller electrodes and most often in a "4X1 ring" montage (center anode electrode surrounded by four return cathode electrodes). This HD-tDCS montage delivers a precise current to the intended target site and has been found to be well tolerated and safe for healthy humans. Furthermore, the utilization of HD-tDCS can facilitate the elucidation of mechanisms of action that can provide greater clarity regarding discrepant results in the literature and for considering future advancements in enhancing effective HD-tDCS implementation strategies. HD-tDCS stimulation increases the membrane potential by several millivolts without triggering an action potential.