Stimulating the Brain

We’ve known about magnetism itself for a long time. We’ve used it and relied upon it for centuries. We even understand how it works. Still it continues to fascinate and mystify us. There was even a time when some people believed that magnetism could control the mind.

But transcranial magnetic stimulation is not science fiction nor is it a new age fad. It’s a safe, non-invasive procedure that uses electromagnetic energy to stimulate the brain. TMS has been used in research since 1985. Since the late 1990s, it’s also been used clinically, not only as a treatment for depression, but for several other conditions as well.

We already have a treatment that uses electricity to stimulate the brain. Electroconvulsive therapy (ECT) has been around for over 70 years and is still considered to be the “gold standard” for treatment of severe depression. Although it is generally regarded as being effective, it is interesting to note that ECT was approved for use before the FDA existed. There have been no randomized controlled studies regarding the effectiveness of ECT since the 1980s. In fact, the FDA is currently considering reclassifying ECT devices and possibly requiring new studies to be done in order to demonstrate safety and efficacy.

In recent years, implanted electrodes have also been introduced, such as the vagus nerve stimulator (VNS). This is a very invasive treatment that involves surgically implanting the device in the neck and attaching it to the vagus nerve. Although it has been approved by the FDA, it is rarely used, not only because of concerns about safety, but also because it has not been very effective. Another still experimental device for treating depression is deep brain stimulation, which is also a neurosurgical procedure that is very risky and highly invasive.

Not only is TMS safe and effective, but it doesn’t even involve the use of electrodes. That’s because electricity and magnetism are two different aspects of the same phenomenon. Every electrical current generates a magnetic field and a magnetic field can cause an electrical current to flow in a nearby conductor. This was discovered almost 200 years ago by the English physicist Michael Faraday.

TMS takes advantage of this relationship between electricity and magnetism by using an electrical current to generate a magnetic field which then induces an electrical current in the brain. So transcranial magnetic stimulation is actually transcranial electrical stimulation, but without the use of electrodes. The therapeutic effect from TMS doesn’t come from the magnetic field itself but rather, from the electrical current which it induces.