Collaborating across schools to help stroke survivors and others, researchers are imaging brain activity in humans in everyday settings
By Patrick L. Kennedy
Today, when a stroke impairs your mobility, a doctor might prescribe a cane to help you walk. In the future, instead of a cane, you might get a robotic exosuit installed with a program that anticipates your every step, so you can smoothly walk down the street without giving it a thought.
That’s just one of a slew of technologies emerging from multiple multidisciplinary BU labs that promise not only to change the way we see and understand the human brain, but also to restore function to people impacted by neurological disorders, helping them to again navigate their homes and communities. Professor David Boas (BME, ECE), founder and director of the BU Neurophotonics Center, calls this cohering, multifaceted field Neuroscience in the Everyday World (NEW). “These are technologies that are really advancing our ability to measure brain function and brain behavior under naturalistic conditions,” Boas says. “So we’re taking neuroscience out of the lab and into the everyday world.”
Using light to understand the brain
Boas and colleagues have developed one of the most prominent of the NEW technologies: wearable functional near-infrared spectroscopy (fNIRS). There are a few variations on wearable fNIRS for different applications, but they all use light to track the flow of blood to the different regions of the brain as a way to learn which neurons are activated by what stimuli and behaviors.
For three decades, the standard way to track blood flow in the brain has been functional magnetic resonance imaging (fMRI). “That revolutionized our understanding of the brain,” says Boas. “It requires the subject, however, to lie down inside a magnet, and when they’re inside the magnet, they can’t be engaging in actual naturalistic tasks.”
Near-infrared light can be used in neural imaging because it can travel far into brain tissue, but it’s absorbed by hemoglobin. “So if the amount of hemoglobin in the brain changes, as it does during brain activity, it will change the amount of absorbed light, and we can detect that,” says Boas. Subjects in fNIRS studies wear a kind of cap covered with light sources and detectors. “By measuring the temporal changes in the amount of light we detect, we can infer what brain regions are being activated.”
By making this fNIRS system wearable, Boas and colleagues can now study subjects as they move about in public, perceiving and interacting with their environment. The richer set of data the researchers thereby gain will lead to a new understanding of the links between brain activity and behavior, benefitting a variety of future researchers, clinicians, and patients.
“The classic complaint about the engineer is that they build a hammer and then are looking for a nail, but I’m really scouring the earth for the right nail,” Boas says. “We’re not just developing technologies but really following them through to make sure they can have the most societal impact. I’ve got so many colleagues doing amazing things with this system.”
Walking without thinking about it
One of these colleagues is Louis Awad, an associate professor of physical therapy at the BU Sargent College of Health & Rehabilitation Sciences and the director of the Neuromotor Recovery Laboratory, which creates new technologies to help patients with neuromotor impairments—such as stroke, multiple sclerosis, and Parkinson’s disease—regain their mobility.
“We’re trying to develop the next generation of wearable sensing technologies that can give us a better sense of different things that matter to how patients move in the everyday world,” says Awad.
One element of mobility that neuromotor-impaired patients often lose is automaticity—the ability to walk without thinking about it consciously. Ordinarily, we take automaticity for granted, says Awad. “You’re not thinking about putting one foot in front of the other, or the timing of muscle contractions.” Awad’s patients must do this deliberately, which distracts their brains from other planning tasks.
But it’s impossible for rehab researchers, let alone physical therapists, to understand exactly what’s going on in a patient’s brain simply by watching them walk. “We’re blind to the neural strategy underlying real-world mobility,” Awad says. “If our goal is to restore effortless walking, we need to be able to see into the brain.”
With Boas, Research Associate Professor Meryem Ayşe Yücel (BME) and others, Awad has devised the Robotic Exosuit Augmented Locomotion (REAL) system. Like other exosuits in Awad’s lab, this is a textile-based active assistive device, meaning it uses soft robotics and powered cables to help restore a patient’s gait after a stroke. But wearable fNIRS adds another dimension to the system.
Unlike a simpler robotic exosuit, wearable fNIRS can forecast a patient’s next move. “We can predict, 100 milliseconds into the future, what they’re going to be doing,” Awad says. “Because if we’re always playing catch-up—seeing what the patient is doing, then trying to assist—we’re never going to make this a fluid interaction. But having the fNIRS technology from David’s team means we can track the neural signal as it’s originating in the brain.”
That information is fed back to the robotic system that’s assisting the wearer’s movements. “It makes for a more seamless integration,” enabling the robot to carry out the human’s intent without frustrating delays, Awad says. “It gets back to that automaticity of movement.”
In one study, using the REAL system in parallel with fNIRS helped patients move in an automatic way—walking up and down the aisles of a parking garage—so that they could focus their brain on a cognitive task, finding their car. “This is true neuroscience in the everyday world,” says Awad. “Not just as a measurement but as a treatment.”
Awad’s father and uncle both had strokes within six months of each other when Awad was a teenager, which is what started him on the path to rehab science. “If the doctors had told me, ‘Your uncle will never fully recover the ability to control his own muscles, but we have a wearable exosuit that will enable him to move the way he wants to whenever he wants, and to reintegrate into everyday life,’ I would have accepted that in a heartbeat,” Awad says. “Maybe that’s not biological recovery, but it is functional recovery, and I think we can achieve that within the next couple of decades.”
A normal conversation
Swathi Kiran also works with stroke survivors and people with dementia, Parkinson’s disease, and traumatic brain injuries. But while Awad focuses on patients’ gait, Kiran studies their speech. The James and Cecilia Tse Ying Professor in Neurorehabilitation at Sargent College, Kiran is the director of the Center for Brain Recovery (CBR) as well as the research director of the Aphasia Resource Center.
As in Awad’s lab, Kiran and colleagues at the CBR are not just doing basic science; they’re helping real patients who suffer from neurological disorders by developing and testing better therapies.
“When you have neurological disorders like stroke and dementia, you have trouble speaking, understanding what people are saying, and remembering things,” says Kiran. The researchers want to see brain activity while patients try to remember and communicate.
“Before we started using fNIRS, our only option was to put folks in an MRI scanner—a big magnet—and scan their brains while they’re lying still and can’t really talk,” Kiran says of fMRI scans. “With fNIRS, we can sit across from each other normally while patients are wearing the cap and do the experiments while just having a normal conversation.”
While subjects converse thus, the sensors measure brain regions that are involved in language processing and planning. In the case of dementia, the experiments could lead to methods of early detection. “We’re looking for a marker,” Kiran says, “brain activation patterns showing that something is clearly going on.”
In the future, Kiran says, aging people who are showing what could be early signs of dementia, or not—for example, staying home a lot because they’re worried about falls or anxious about their language or memory—will be able to take a test similar to what Kiran is conducting at BU. “They can come in to monitor their brain,” she says. “It’s not invasive, it’s quick and easy, and the goal is to detect changes in brain function earlier, before the disease has set in.”
In the case of stroke, where the damage has already occurred, the goal of tests using fNIRS is to assess the extent of the damage, as well as the effectiveness of treatment. “We’d like to see if the brain is changing as a function of the intervention,” says Kiran. “We can measure their brains before and after the therapy to see what in the brain has changed.”
The wearable fNIRS system “has opened up a whole new avenue of research we didn’t think about before,” Kiran says. “It’s made some of this work more practical and not just lab-based.”
That’s a result, she adds, of the collaboration of experts across disciplines.
“I’m a trained speech language pathologist, and at some point I realized that we couldn’t help the patients fully change their lives unless we reached out of our comfort zone and really tried to make a bigger difference,” she says. “So almost everything we do [at the CBR] is a convergence, with neurology, biomedical engineering, computer science, and data science all working on the same problem. I think that’s the future.”
Advancing neuroscience in the everyday world (NEW)
These are just a handful of the groundbreaking neuroscience technologies coming out of labs where ENG faculty work with colleagues from other BU schools. Boas and ENG colleagues such as Professor Anna Devor (BME) and Assistant Professor Matthias Stangl (BME, psychological and brain sciences, neurosurgery) have landed several NIH grants to advance the Neuroscience in the Everyday World field in conjunction with collaborators from the BU Chobanian & Avedisian School of Medicine, Massachusetts General Hospital, and other institutions.
For example, Boas is part of a large, multi-institution NIH grant to map the billions of neurons in the human brain. He calls it a “multiscale atlas akin to Google Earth for the human brainstem.”
“The convergent aspect can’t be emphasized enough,” says Awad. “It’s not just cool technology, it’s truly bringing labs together to solve problems that we couldn’t solve alone. That’s what’s special about BU.”
Learn more about fNIRS at the website of the