Electrically stimulating the brain’s cortex in patients with Parkinson’s disease may improve motor symptoms.
Reza Shadmehr, PhD, of Johns Hopkins University School of Medicine, Baltimore, and colleagues enrolled 30 older adults, half of whom had been diagnosed with Parkinson’s. They were then asked to grip handles at the end of supports in order to measure the force applied to them. The participants needed to use force on the handles in order to move a cursor on a computer screen.
During the experiment, the healthy participants tended to divide the four pounds of force needed to move the cursor between both arms. However, the Parkinson’s patients tended to favor much more strongly their arm that was lest affected by motor system difficulties, the researchers reported in The Journal of Neuroscience.
In Parkinson’s, dopamine neurons tend to die on one side of the brain, which impacts the ability of an individual to exert pressure on the opposite side of their body.
The researchers then used transcranial direct current stimulation (tDCS) on 25 patients, wuith the idea that the electric current would help the remaining dopamine cells fire better, helping the brain engage more. Patients who received tDCS were more willing to use their affected arm in the task compared to those who received no stimulation. Also, the stimulation led to an average 25% improvement in motor symptoms, based on the Unified Parkinson's Disease Rating Scale.
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.