Resetting the Brain

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That may sound a lot like electroconvulsive (or electroshock) therapy, but it's not. "Magnetic stimulation is a clever way to induce current without actually having an electrical connection," says Dr. George Wittenberg, a neurologist at Wake Forest University, who is studying magnetic pulses for their potential to help stroke patients recover more quickly. Unlike electroconvulsive therapy, which affects the whole brain, the magnets are focused only on specific regions at the surface, or cortex. And because the treatment does not trigger a seizure (as electroconvulsive therapy does), there's no need for muscle relaxants or anesthesia and no problem with memory loss. Patients undergoing magnetic stimulation usually feel only a kind of tapping on their skull as the current starts to flow.

Why would anyone want to generate tiny electrical currents in their brain? "You have to remember the brain is both an electrical and a chemical organ," says Dr. Mark George, a psychiatrist at the Medical University of South Carolina who is investigating magnetic stimulation as a treatment for depression for the NIMH. Drugs like Prozac and Zoloft address chemical imbalances, but that's only part of the problem. Electroconvulsive therapy, despite its troubling side effects, is still one of the most effective treatments available for severe, unrelenting depression.

Although researchers freely confess that they don't know how rTMS works, they do have some ideas. It has long been clear that neurons in different parts of the brain can act in concert. Of particular interest are the circuits that link the areas of the cortex that help us reason and plan our lives with more deeply embedded zones of the brain such as the limbic system, where emotions are processed. One theory holds that depression is either caused by or results in an imbalance in the activity in those regions. Applying periodic bursts of electrical current at the cortex may reset the network in a process that's akin to rebooting a computer.

No one knows how long such a reset might last and whether aiming the magnet at a different part of the brain would work any better. But that hasn't stopped neurologists from trying rTMS on other conditions. For example, specialized MRI scans can pinpoint where stroke damage has occurred and what parts of the brain are trying to take over for the affected regions. Could the right combination of stimulation and inhibition help stroke victims overcome their disabilities?

At Wayne State University in Detroit, Dr. Randall Benson is studying 28 stroke patients to see if he can enhance their impaired speech after existing therapies are no longer effective. First they undergo a brain scan to see which of their language centers are still at least partially active. Then Benson targets those regions with rTMS. "Because things like language are regulated in the brain by a network, when we stimulate in one place, we find activation all over the brain," Benson says.