This Treadmill May Help Unlock Secrets to Parkinson’s Disease
Researchers are investigating what causes patients to freeze while walking and how it can be avoided.
Riley takes a few easy strides on the oversized treadmill.
Two small reflective spheres extend from his shoulders like alien antenna — sensors for the 14 motion capture cameras mounted around the periphery of a 13-by-8 foot projection screen on the front wall. Each step moves him forward down the long, gray hallway punctuated with paintings and corridors projected on the screen in front of him.
His walking pace is relaxed. Riley follows a green line in the center of the faux-wood floor past the paintings on the wall and corridors that extend to the left and right.
“Does that feel good, Riley, that speed?” asks Elizabeth Hardin, PhD, an investigator at the Cleveland FES Center.
An exercise science intern from the University of Rhode Island, Riley nods as he continues walking in place on the dual-belt force-instrumented treadmill. For the next 30 seconds, his pace matches the relative speed of the hallway he’s navigating in the Virtual Reality Human Performance Laboratory in the lower level of the Louis Stokes Cleveland VA Medical Center.
Developed to measure balance and gait under real-world conditions, the lab uses movement analysis to improve the function of patients suffering from neurological, orthopedic and musculoskeletal disorders, as well as limb loss. It provides interactive and real-time visual and auditory feedback for evaluation, as well as accurate biomechanical measurements and gait training tools to improve balance and mobility.
“Most people who experience our VR system say, ‘You know what? It didn’t feel like a cartoon to me. It felt like I was walking in a real hallway,’” says Hardin.
With interests in human walking performance and stability, Hardin is part of a team using virtual reality to research a symptom of Parkinson’s disease known as freezing of gait. Hardin and her colleagues postulate that the phenomena — in which a patient’s feet seem stuck to the floor — may be triggered by increased optical flow, where the environment seems to be moving at heightened speed.
Hardin adjusts the projection on the screen to ten-times walking speed, so it appears Riley is running down the corridor. Yet the treadmill remains at the previous pace. This simulates what might happen when a Parkinson’s patient moves from a large, open area like the produce section of a grocery store to the store’s aisles where the space is more constrained. It’s these shifts in visual markers that often stop patients in their tracks.
“Then they just can’t walk anymore,” she says. “They freeze.”
Three Studies
Hardin is collaborating with Aasef Shaikh, MD, PhD, an investigator at the Cleveland FES Center and neurologist at both the Cleveland VA Medical Center and University Hospitals Cleveland Medical Center.
Their work is part of a study funded by a three-year, $240,000 grant from the American Parkinson Disease Association. An estimated 1 million people have Parkinson’s in the United States with an additional 50,000 new diagnoses each year.
In addition to this study, Shaikh has two other ongoing projects at the Cleveland FES Center.
In one, Shaikh joined Cameron McIntyre, PhD, a fellow investigator and associate director of industry relations at the FES Center, to conduct behavioral experiments with motion simulators similar to those used by NASA to train astronauts.
“We are studying how participants with Parkinson’s perceive their own directional heading,” says Shaikh, “whether they are going straight ahead or veering to the side.”
Parkinson’s patients with deep brain stimulation implants sit in a simulator. As the chair is rotated, the brain stimulation is turned on and off to determine if it makes a difference in perception of motion. That information is then combined with MRI images of the participants’ brains and bioelectric field stimulation models developed by McIntyre.
“Together, this gives us a sort of 3D picture of everything involved in the process,” says
Shaikh. “That allows us to understand how participants with Parkinson’s perceive their own directional heading.”
In his most recent research project, Shaikh and Fatema Ghasia, MD, a pediatric ophthalmologist and adult strabismus surgeon at Cleveland Clinic, are examining how Parkinson’s patients “search and scan” their surroundings as they navigate their environment. That’s because up to 20 percent of those with Parkinson’s develop double vision due to eye misalignment and trouble with depth perception.
The researchers record eye, head and limb movement simultaneously to look for abnormal eye movements that are separate from the head oscillation and tremors symptomatic of Parkinson’s. The idea is to evaluate the effects of deep brain stimulation on these vision issues, especially binocular coordination of eye movements.
“Through our research, we are beginning to understand more and more about which particular pathways and structures are responsible for perception of motion and heading perception in humans,” says Shaikh.
Stepping Out
Back in the virtual reality lab, the gait freezing trial Hardin and Shaikh are working on involves about 60 individuals with a third in a control group, a third taking medication for their Parkinson’s and a third being treated with deep brain stimulation.
“We’re trying to determine if there’s a biomarker for freezing,” Hardin says. “Because the onset of Parkinson’s may happen much earlier in somebody’s life than can currently be detected.”
Riley, who’s just demonstrating the technology and not actually a research participant, wears sensors positioned on his shoulders, ankles and waist. Taken together, the points are part of a 3-D model that Hardin can evaluate.
“We can determine where their center of mass is in space,” she says. “How is it moving? Is it smooth? Is it being perturbed? Is it drifting right or left?”
Hardin stops the treadmill. “You walked 99 meters,” she tells Riley.
Then she calls up a previous session on the computer screen next to her. A stick figure animation begins walking just like Riley. But at a point, the figure starts falling behind on the treadmill with erratic surges in the individual’s stepping.
“This session was very scary to me,” she says. “Toward the end here, he’s really drifting to the back. So, we had to stop him.”
While Hardin and Shaikh have created the freezing gait phenomena in some participants, they’re also working to find the best way to treat it — whether that’s with medication, deep brain stimulation or a combination.
“In the future, we hope the much broader application of our work beyond Parkinson’s will be to use similar concepts and strategies to treat balance function or navigational problems in patients with any condition,” says Shaikh.
