Brain Device May Trigger Impulsiveness
Brain Implant That Stops Tremors of Parkinson's Disease May Block Impulse-Control SignalDon Falk looks at the CAT scan showing the implant into his brain to help control his Parkinsons disease. Falk's condition started to get better with the emerging class of medical devices called neuromodulators. He is shown Feb. 3, 2006, in St. Louis Park, Minn
Michael Frank did what any thoughtful person would. He asked a patient suffering from Parkinson's disease if he would like to sit in a more comfortable chair across the room.
However, instead of taking a moment to think about it, the patient immediately stood up and tried to get to the chair -- completely ignoring the fact he was unable to walk.
"He couldn't walk without a wheelchair, and I had to help to prevent him from falling down," says Frank, an assistant professor of psychology at the University of Arizona at Tucson. "He saw the chair, thought it was a good idea, and got up to walk toward it without really thinking about his condition."
This kind of impulsive behavior may be a side effect of deep brain stimulation that is used to treat Parkinson's disease. Deep brain stimulation helps some patients control debilitating tremors, but new research suggests it may also impair decision making.
In a new study to be published in the journal Science, researchers found that when Parkinson's patients received brain stimulation, they had trouble making hard decisions. However, when the stimulation was turned off, patients responded like the healthy individuals in the control study.
"From a scientific point of view, this research provides light on how some of the circuitry involved in decision making works in the brain," says study co-author Scott Sherman, a professor of neuroscience at the University of Arizona.
"For Parkinson's patients, this study highlights the fact that there are side effects to most interventions," he says. "Even though patients know they have balance problems and are at risk for falling, they may still act impulsively. Patients may gain more mobility with deep brain stimulation, only to experience more falls."
A Shock to Block Tremors
Parkinson's disease is caused by the degradation of nerve cells in the brain that produce dopamine, a signaling chemical that is necessary for smooth and controlled muscular movement.
When these dopamine-containing cells are destroyed, people experience tremors, muscle rigidity and difficulty walking and balancing -- symptoms that only worsen with time.
Looking for hidden signs of consciousness
A team, led by Adrian Owen of the MRC Cognition and Brain Sciences Unit in Cambridge, UK, used functional magnetic resonance imaging (fMRI) to show that a woman left in a vegetative state after a car accident could respond to requests to imagine playing tennis or navigate around her house (A. Owen et al. Science 313, 1402; 2006)... Laureys, a member of this team, has now tested this technique on 24 healthy volunteers, who were similarly instructed to imagine either walking around their house or playing tennis. The tasks activate separate networks in the brain, and the scans proved able to tell correctly which task was being performed (M. Boly et al. NeuroImage doi:10.1016/j.neuroimage.2007.02.047; 2007)...showing that the method works reliably in healthy brains proves its robustness. "Our challenge is to find markers that tell us 'this is a hopeless case' or 'this is a case where we should increase our therapeutic efforts'," says Laureys.