Shocks switch brain on

---

Fonte

Electric implants may ease Parkinson's by stimulating nerves.
November 2002
HELEN PEARSON

Electrodes inside the brain can quell involuntary movement.

Stimulating brain activity, not dulling it, might be the secret of a treatment for Parkinson's disease, say neuroscientists. The therapy may soon be used to treat psychiatric disorders.

The technique, called deep brain stimulation, uses tiny buried electrodes to stimulate regions of the brain. How it works is obscure, doctors told the Society for Neuroscience meeting in Orlando, Florida.

The mild current had been thought to stifle overactive regions that cause disease. But in some cases, it may boost nerves' activity and change their firing patterns, says Jerrold Vitek of Emory University, Atlanta, who works on a monkey version of Parkinson's.

Vitek and his colleagues implanted electrodes in monkeys' subthalamic nuclei, one of the brain regions targeted in Parkinson's treatments. The shocks were thought to reduce patients' involuntary movements by quelling another region called the globus pallidus.

In fact, stimulating the subthalamic nucleus boosted the globus pallidus. Yet the animals' symptoms improved. "When I first saw the results, I didn't believe them," says Vitek.

The team realized that, despite being more active, the globus pallidus was firing more steadily. "The regular pattern is probably the critical factor," says Vitek.

"[Electrical stimulation] knocks out the abnormality and replaces it with a new signal, " suggests Jonathan Dostrovsky of the University of Toronto, Canada, one of several other researchers to present evidence on the therapy.

Scientists at the meeting agreed that the effects of deep brain stimulation are far more complex than was once thought. Shocking one spot in the brain will affect many others, and numerous mechanisms are probably at work. "You've got to be surprised it even works," says Vitek.

Despite their ignorance, doctors are hoping to broaden the therapy to treat obsessive-compulsive disorder, epilepsy and anorexia nervosa. "We need to know what we're doing," says Robert Gross, also at Emory. "It'll enable us to be more efficient in developing new techniques."

The long-term effects of deep brain stimulation are even less clear. In June, the US National Institutes of Health set up a consortium to try to get to the root of the mechanism.

� Nature News Service / Macmillan Magazines Ltd 2002