A volunteer models
the noninvasive, electrical stimulation device
used in this
study. Reza Shadmehr, Johns Hopkins Medicine
FAST FACTS:
* 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.