Direct Current Brain Polarization: A Simple, Noninvasive Technique for Human Neuromodulation

Objectives:  It has been known for decades that neurons in vitro and in vivo respond in a polarity‐specific manner to changes in their electrical environment. Likewise, investigators have passed direct current (DC) across the human head for decades in attempts to alter brain function and behavior. Recent human data, however, have put this technique on a more solid empirical footing and it has re‐emerged from obscurity as a “new,” noninvasive means of neuromodulation, called transcranial direct current stimulation (TDCS). Materials and Methods:  Here, we offer a selective literature review together with our own research on the basic mechanisms and human applications of TDCS in neurophysiologic, cognitive, and behavioral research. We discuss a possible role for TDCS in enhancing normal brain function and treating neurologic and behavioral disorders. Results:  While there are uncertainties about how TDCS produces behavioral effects and how the current is distributed in the human brain, TDCS has safely produced a variety effects on human brain function in small studies. Conclusions:  The field is very young and many findings will require replication. Nevertheless, TDCS appears to have the potential to be a simple and safe means of neuromodulation.