Lab report: Inside the neurorobotics research group lab

CC scientists use functional neuroimaging, neural interfacing and rehabilitation robotics to evaluate and treat movement disorders

If there was a Bat Cave for the intersection of rehabilitation medicine and robotics engineering, the newly renovated 900-square-foot lab in Building 21 on the NIH campus in Bethesda, Md., occupied by the Neurorobotics Research Group, or NRG ("energy" acronym intended), would be it.

Part of the Neurorehabilitation and Biomechanics Sections of the Clinical Center's Rehabilitation Medicine Department, the group is led by principal investigator Dr. Tom Bulea, an engineer who develops novel technologies to improve the lives of people with neurological disorders. Or, as Bulea has written, "We combine neuroscience and engineering principles to create new rehabilitation paradigms that maximize functional outcomes by optimizing human-machine interaction."

Bulea and his colleagues, including Dr. Diane Damiano, a senior investigator in the CC's Rehabilitation Medicine Department, are perhaps best-known for their work on a leg-brace robotic prothesis that helps pediatric patients with cerebral palsy correct a knee extension gait deficiency.

Thanks to a cooperative research and development agreement with the Canadian company Bionic Power, the slimmed-down, light-weight device is now in its fourth iteration and undergoing observational clinical testing at the NIH CC and an at-home interventional trial. This work is supported by first year post-baccalaureate fellow Jordan Dembsky, who works with study participants in the CC gait lab and conducts computer analysis of their recorded biomechanics data.

Meanwhile, Dr. Mohamed Abdelhady, a post-doctoral fellow from Cleveland State University, is working to make the exoskeleton more adaptive. The goal, Bulea says, “is to provide training not only when kids walk, but while they do all the other things kids do—start, stop, squat and jump.”

The exoskeleton is just one of many early and late-stage research projects currently underway at the six-person lab, which includes a newly hired part-time research physical therapist and a planned staff scientist by year’s end. Together, they draw upon a range of disciplines—from engineering, robotics, and machine learning to neuroscience, physical therapy, and rehabilitation medicine—in their quest to develop new investigative and therapeutic tools.  

One of the longest-serving members of the upstart NRG lab is Kevin Rao, a biomedical engineering major from Johns Hopkins, who is now in his second and final year of a post-bac fellowship. Rao is working on two pilot projects in addition to the exoskeleton initiative. One is a sensory restoration prothesis for individuals who lack proprioception, an extremely rare genetic disorder caused by the PIEZO2 gene first implicated in human mechanosensation by NIH researchers. Absent proprioception, people have no relative sense of their body position in space.

Working with Dr. Alex Chesler, of the National Center for Complementary and Integrative Health and Dr. Carsten Bönnemann, of the National Institute of Neurological Disorders and Stroke, as well as researchers at Stanford, Rao and his NRG colleagues are taking a first step to characterize the psychophysics of deep pressure sensation in the skin.

“We’re trying to identify both what people consider deep pressure, the thresholds for what deep pressure is, and how it relates to touch threshold and pain threshold,” Bulea explains.

The goal is to create a wearable device that maps limb movement to alternative sensory inputs as a type of sensory “prothesis”. To date, the number of known cases of PIEZO2 loss of function (LOF) disorder world-wide measures in the dozens. While the research collaboration could ultimately benefit those individuals, Bulea and Rao say the applications are potentially far broader.

“It’s a very unique clinical population and it kind of proposes a really interesting learning opportunity, because they’ve never had any form of sensory proprioceptive feedback,” Bulea notes. 

By studying how research volunteers with PIEZO2 disorder incorporate and integrate substituted feedback to adapt their motor control “we’ll be able to better design alternate sensory inputs for people not with complete loss, but some absence or deficiencies,” Bulea says. 

That far larger group potentially includes people afflicted by strokes, Parkinson’s disease or cerebral palsy.

Also working in the lab is Dr. Shriniwas Patwardhan, a post-doc fellow from George Mason University, who is working on early-stage research-and-development projects to measure and quantify movement to improve methods of controlling robotics and interventions. 

Patwardhan’s expertise lies in the use of ultrasound to infer motor intent (or desired muscle movements) in people with neurological disorders.

Citing the example of the lab’s exoskeleton device, Patwardhan notes the two key aspects underlying its effectiveness—understanding what the user is trying to do and the ability to support or modulate that movement. “Understanding motor intent is a big key,” Patwardhan says.

He notes that NRG’s exoskeleton currently tracks the user’s movements and interaction forces to drive the device robot. Elsewhere, experts employ EMG, or electromyography, which uses sensors to measure the electrical stimulation in muscle tissue to make inferences about users’ intended movement. “But in my PhD work, we actually used ultrasound to do that exact same thing,” Patwardhan says. 

Unlike the toaster-oven-size ultrasound devices one might associate with the wellness checks of pregnant mothers, Patwardhan used micro-size ultrasound devices no bigger than a quarter. “It turns out that when an amputee imagines doing a certain movement, say two different patterns of thumb movement or pinky movement, that results in very different muscle deformation patterns in their forearm when they’re imaging a phantom limb moving.”

Ultrasound can detect subtle changes in muscle thickness, size, and shape during those moments. The question Drs. Bulea and Patwardhan and their NRG colleagues are now just starting to try to answer is, does that approach lend itself to other pathologies beyond those with amputations?

The project is just one of many high-risk, high-reward research endeavors Bulea and his colleagues are undertaking in NRG’s upstart lab. Others include Bulea’s efforts to apply the well-trod ground of electrical stimulation of muscles in novel ways to create new tools to aid rehabilitation in children with neurological movement disorders, such as cerebral palsy. 

“We [have] done some pilot stuff with surface stimulation and have shown you can get some surprisingly good … acute results,” he says.

Another research area focuses on mobile brain-body imaging, using electroencephalography (EEG) in combination with motion capture video and electromyography (EMG) to study brain activity during functional movements. This line of research began during his time as a staff scientist with Dr. Damiano, who recognized the potential clinical applications of this technology in children with movement disorders. Bulea says the approach enables his lab to look at how brain activity that coordinates and executes movements is altered in people with movement disorders. “How do those patterns change over time throughout development in childhood, or before and after an intervention, as you gain motor skill?” Bulea wonders. The answers may reveal new biomarkers, or indicators of disease, and the link between cortical activity and skill level in functional movement.

The payoff, Bulea says, would be the discovery of new ways to assess the effectiveness of interventions and optimize their design. “By looking at quantifying cortical activity before and after an intervention or even during an intervention,” Bulea says, “we can see if we’re coaching [patients] in the right direction.”

The project encapsulates what Bulea says is his fundamental drive as a scientist and the NRG lab he leads—taking a broad view to understand the neural control of movement and “then using that to develop new technology to help people improve the way they move their bodies.”

- Sean Markey