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Wednesday, Oct. 29, 2008
TMS can reach parts of the brain conventional treatments may not
By ROWAN HOOPER
I am in a windowless basement in central London with two men I've only just met. It sounds like this story could veer toward the salacious, but bear with me.
The men boot up computers and switch on an electrical capacitor, which makes a low hum. I am asked if I have ever had any heart problems or epilepsy, or if I am on medication. No, no and no. "OK then," one of the men says, "here we go."
He picks up a plastic-covered rod that looks like something you might beat a carpet with, smaller than a tennis racket, with a figure-8 shape on the end and a cable attached to the handle. He places the wand on the crown of my head and tells the other man, "Energize."
It may sound like this is an episode of "Star Trek," but it is in fact transcranial magnetic stimulation (TMS): a kind of magnetic brain therapy that is generating increasing interest around the world.
The basement where I'm being zapped is in the Institute of Cognitive Neuroscience at University College London. Inside the figure 8 held against my head is a coil of wire. The capacitor sends electrical charges through the coil, charges that create magnetic fields and change the electrical activity in my brain.
The procedure is being used as treatment for schizophrenia, depression, migraine and stroke, among other things. TMS has also been used to treat Parkinson's disease and Alzheimer's, and even to rouse a man from a coma.
The idea is that the electromagnetism produced by the coil makes neurons in the brain fire more or less, and so communicate with each other to a greater or lesser extent. The coil doesn't just stimulate the entire brain, but specific regions, and the trick is to zone in on the precise region you want to affect.
Vincent Walsh, the neuroscientist messing with my head in the basement, demonstrates. First, he does so by sending zaps through my head and locating the correct position to show me how he can stop me controlling my own arm.
He holds a £10 note in front of me, and asks me to take it from him. As I reach for it, he zaps me, aiming for the motor-control part of my brain.
My arm jerks away of its own accord and I am unable to grasp the money. The zap feels like someone has tapped their knuckles on my skull; it isn't painful, but it does feel odd. With one zap like this, lasting only milliseconds, the effect wears off very quickly, and a moment later I am able to get my hands on the money.
Then Walsh tries to position the zapper so that it targets a certain part of the frontal lobe of my cortex, an area that controls speech production. He has me repeat a nursery rhyme: "Baa-baa black sheep . . . "
When I reach the "sh" of "sheep," he zaps me, and for a second I stutter on the word, and can't get it out. He has interrupted the firing of the neurons in my brain that control speech processing and production. It's a weird feeling.
All that was great fun, but repeated stimulation — or inhibition — of particular regions of the brain can have longer term, therapeutic value.
To treat depression, for example, the magnetic energy is aimed specifically at a portion of the brain called the left prefrontal cortex, which is thought to be involved with mood regulation.
To test the effectiveness of the TMS treatment, patients with depression underwent 45-minute sessions for four to six weeks.
Half were given TMS, half had a "sham" placebo treatment — although neither group knew whether they were getting real TMS treatment or not. The results showed that people on the real TMS treatment received twice the reduction of symptoms as those in the sham trial.
For patients with schizophrenia, the zaps are directed at the so-called Wernicke's region in the left temporal lobe, and a second region located on the opposite side of the brain. Patients undergoing 16-minute sessions daily for three weeks showed reductions in the hallucinatory voices they had been hearing.
TMS is also being used to try to boost memory, which is one of the brain functions lost in Alzheimer's disease. Also, in people who suffer migraines, TMS is showing promise as a treatment to prevent the throbbing headaches that follow the "aura" phase of early migraine, when the sufferer experiences flashing lights and stars.
And in a big boost for the method, TMS recently received approval from the U.S. Food and Drug Administration — the all-important green light for physicians. The FDA says TMS can now be used to treat depression in patients who don't respond to drugs.
I think this can only be a good thing — TMS is a noninvasive method and, although it doesn't work on all patients, it has fascinating potential. The technique has been around for more than 20 years, and FDA approval could be just the boost it needs.
The second volume of Natural Selections translated into Japanese is published by Shinchosha at ¥1,500, titled "Hito wa Ima mo Shinka Shiteru (The Evolving Human: How New Biology Explains Your Journey Through Life)."