By William J. Cromie
Alvaro Pascual-Leone can make a depressed person feel good just by waving a wand over her head.
He can speed up the slow, stiff movements of a patient with Parkinson's disease the same way. The magnetic wand helps schizophrenics and obsessive-compulsives control their behavior, and it can even push blind people to learn Braille more quickly.
Pascual-Leone is no sci-fi sorcerer. An associate professor of medicine at Harvard Medical School, he has experimented with the effects of magnetic and electrical fields on the brain for more than 10 years.
His research shows that magnetic fields from a hand-held wand generate electric currents in a person's brain, and that such currents can be used to learn how the brain works. He and his colleagues mapped the locations of cerebral areas that control language, memory, and attention. Then, they showed how those functions are blocked or enhanced when electric currents increase or decrease the activity of selected brain cells.
The wand generates a magnetic field when electric coils and capacitors switch on and off rapidly. The field, in turn, induces secondary electric currents inside the skull or cranium. It works much like a transformer.
"We believe that transcranial magnetic stimulation (TMS) works by normalizing disturbed levels of brain activity," Pascual-Leone says. "For example, depression and Parkinson's disease both involve decreased levels of activity in specific areas of the brain. Dystonia [muscle rigidity], obsessive-compulsive behavior, and mania are associated with increased activity. Therefore, if we know the part of the brain where activity is abnormal, we should be able to 'fix' it with magnetic stimulation."
Experiments by Pascual-Leone's team at the Beth Israel Deaconess Medical Center in Boston demonstrate how behavior changes the brain and vice versa. When blind people learn Braille, the brain area that controls their reading finger becomes more active and enlarged. By magnetically stimulating this area, the experimenters can increase the Braille reading speed of newly blind people.
"We believe that these results, although preliminary, illustrate the possibility of using the technique to accelerate the healing of brain damage produced by strokes and traumatic head injuries," Pascual-Leone notes.
Zapping and Mapping
The biggest advantage of the magnetic wand is its ease of use: just hold it over the right part of the brain. The biggest disadvantage is that the effect stops when experimenters move the wand away.
Proper placement of the wand, together with the correct intensity and frequency of the electric current, for example, will produce a temporary feeling of happiness or sadness in a normal person. But the feeling is fleeting; it's gone with the wand.
This transient effect was initially used to locate areas of the brain involved in language. Stimulating the left front brain of right-handed people can cause them to temporarily lose the ability to speak. They regain it when the wand is turned off.
Locating the language center is something both biologists and surgeons want to do; the former for knowledge's sake, the latter to avoid the area when doing brain surgery. Neurosurgeons at the Massachusetts General Hospital in Boston are testing a system that combines live images of a patient's brain with a computer-controlled robot arm moving a magnetic wand. The latter locates areas on the brain image that control motor functions.
In the late 1980s, while at the University of Minnesota, Pascual-Leone and his colleagues discovered that TMS could temporarily disrupt memory, attention, color vision, and motion vision. Such "knockouts" make virtual patients out of normal people, allowing researchers to determine which areas of the brain are involved in problems such as memory loss.
Mapping brain areas that control motor activity led Pascual-Leone to experiment with Parkinson's patients, since their slowed movements and rigidity are due to decreased activity in these areas. He showed convincingly that TMS increases the speed of movement in selected patients, but not for long
"Daily stimulation for 10 days speeds up movement for days to weeks," Pascual-Leone says. "But that's not long enough. We are now working on ways to make the beneficial changes more permanent. These include experimenting with different frequencies and intensities of currents, and with combining TMS with drugs. If it works well enough, we might be able to design individualized helmets that a patient could use at home."
If this works in Parkinson's, TMS should also provide temporary relief from the symptoms of related diseases such as Huntington's and ALS (amyotrophic lateral sclerosis, or Lou Gehrig's disease). The technique may also aid the recovery of stroke victims.
Researchers at other institutions have done similar experiments on patients with dystonia, myoclonus (muscle spasms), tics, and obsessive-compulsive disorders. In all cases, TMS seems to help, but the effect cannot be sustained.
The same situation exists in treating depression. In one series of experiments, stimulating the left front brain improved the moods of 11 out of 17 badly depressed people. These patients had not been helped by drugs or even electroshock treatment.
Zapping the left side of the brain works best in right-handed people. With left-handers, things get tricky. Some left-handers improve but others need to be stimulated on the right side of their brains.
"If we prolong stimulation for 5 to 10 days, in the left brain for right-handers, and right brain for left-handers, we can extend the benefit up to several months," Pascual-Leone explains.
Physicians in other countries have begun to use TMS to treat depression, but the procedure has not been approved in the United States. Pascual-Leone hopes that it will eventually work well enough so that individualized treatments can be custom designed for each patient.
If waving a wand over a depressed person's brain makes him or her feel good, why not use it to make normal people feel better? Pascual-Leone tried that and the normals wound up feeling sadder. It was only for a moment, but it shows that using TMS can be tricky business.
A Working Mystery
As in depression, the front part of the brain doesn't work properly in schizophrenia, making it another target for TMS. Schizophrenics experience difficulties handling planning and association tasks governed by the frontal lobes. Several researchers in Boston are trying to stimulate increased activity in those areas.
"Results, so far, look good," Pascual-Leone comments, "but much work remains to be done."
All these efforts, he insists, prove the idea that abnormal brain activity underlies a broad variety of mental and physical illnesses, which can be treated by custom-tailoring TMS treatments for each individual.
Despite its promise, Pascual-Leone admits, "we really don't know how it works."
It differs from direct electric shocks given to epileptics and from dramatic electroconvulsive therapy used on depressed people when nothing else seems to work. Pascual-Leone thinks these treatments affect only cells in the top, or thinking, layers of the brain. TMS, he believes, acts on so-called interneurons, cells that connect different parts of the brain.
Stimulating these cells, he says, "opens a window to other regions of the brain," including deeper structures that control emotion and the automatic or instinctive responses we don't think about. He thinks this action accounts for the fact that, with repeated stimulation, some of the beneficial effects can be sustained for months.
Having a way to change behavior, Pascual-Leone comments, "also opens an ethical can of worms."
You might imagine going into a TMS store and putting down $10 or $20 for a "feel good" hit of electric current, or to improve your memory temporarily for a test or job interview. Also, if TMS can help a blind person learn to read Braille more efficiently, could it also help your tennis game, make you a better piano player, or enhance any number or other skills?
Those would not be easy things to do, Pascual-Leone notes. "Remember, TMS can depress normal people, and the same amount of current in different people may produce different results," he says. "Also, many of the effects of TMS in normal people last only seconds.
"In a blind person, the visual cortex of the brain gives up some of its unused capacity to areas dedicated to touch and hearing," he continues. "Although the area with which a blind person reads expands, the part controlling the pinkie gets smaller. In other words, there's probably not much you can change in a normally functioning brain. Humans don't have large areas of brain with nothing to do, so if you make favorable changes in one place, they're likely to produce unfavorable changes elsewhere. If your brain is functioning normally, that's as good as it gets."
Having said those words with some confidence, Pascual-Leone frowns and quietly adds, "but I do worry about some people trying to go beyond that."
Copyright 1998 President and Fellows of Harvard College