A volunteer models the noninvasive, electrical stimulation device
used in this study. Reza Shadmehr, Johns Hopkins Medicine
* People with Parkinson’s disease are still capable of making quick, forceful movements even though most of their movements are slower and less intense than usual.
** Researchers measured the force that patients applied to their affected and less affected arms to achieve a combined target force in a specified direction.
* They found that patients who received noninvasive brain stimulation split the force applied by their arms more evenly and improved motor symptoms in some patients.
(September 10, 2015) People with Parkinson’s disease (PD) tend to slow down and decrease the intensity of their movements even though many retain the ability to move more quickly and forcefully. Now, in proof-of-concept experiments with “joysticks” that measure force, a team of Johns Hopkins scientists report evidence that the slowdown likely arises from the brain’s “cost/benefit analysis,” which gets skewed by the loss of dopamine in people with PD.
In addition, their study with a small group of 20 patients with PD demonstrated that stimulation of the cortex of the brain using external electrodes corrected some of the distortion and temporarily improved some patients’ motor symptoms. PD affects up to 1 million Americans.
“The loss of dopamine associated with Parkinson’s disease makes the effort required to move the affected side of the body seem greater, so the brain is less willing to use that arm to complete tasks,” says Reza Shadmehr, Ph.D., professor of biomedical engineering at the Johns Hopkins University School of Medicine. “Our study suggests that direct current stimulation can compensate somewhat for the loss of dopamine by decreasing the effort the brain has to put into getting its motor neurons to fire,” adds Shadmehr, the senior author of a report on the research published online in The Journal of Neuroscience on Sept. 2.