What is transcranial magnetic stimulation, and what is it used for?

Transcranial magnetic stimulation (TMS) is a method for electrically stimulating the brain from the outside of the skull. This is done by passing a brief, strong current through a coil of wire called the magnetic coil. The current flowing in this way creates a brief magnetic field that passes through the skull without weakening and then electrically stimulates the nerve cells in the brain. The advantage of doing this with magnetic stimulation over just using electrical stimulation is that TMS is virtually painless. 

TMS can be used to probe the excitability of brain circuits, allowing a noninvasive method for looking at brain physiology.  It can also temporarily inactivate part of the brain, which can help illuminate brain function. In addition, TMS can be used to alter brain function; for this purpose TMS might be given in rapid trains or in special patterns. In this regard, TMS may be useful to treat brain disorders.  Already the FDA has approved TMS as a treatment for some types of depression. TMS is an active area of research for learning more about the brain and providing the possibility for new treatments.

About the Author

Mark Hallett

Mark Hallett is Chief of the Human Motor Control Section at NINDS, NIH, where he conducts research on the control of normal human movement and the pathophysiology of different movement disorders. His laboratory was one of the first ones to use transcranial magnetic stimulation (TMS) in the United States and has produced many research papers and reviews about TMS.