18 Nov 2016

Six months after brain-implant surgery, a woman paralyzed from amyotrophic lateral sclerosis was able to channel signals from her motor cortex into words spelled out on a tablet computer, all in the comfort of her own home. The research was presented November 12 at the 2016 Society for Neuroscience Meeting in San Diego and published in that day’s issue of the New England Journal of Medicine. It uses the first fully implantable brain-computer interface (BCI) communication system that allows ongoing use by patients without supervision from researchers. The system is the brainchild of a group led by Nick Ramsey of University Medical Center Utrecht, in the Netherlands.

“The big deal here is that the field is trying to make [BCI] systems that patients can use by themselves,” said Matthias Hohmann, a student researcher at the Max Planck Institute in Tübingen, Germany. “We are now out of the lab, into the homes of people and trying to make it happen.” 

Thoughts into Type. By flexing her motor cortex, Hanneke De Bruijne can communicate with her family and friends. [Courtesy of Nick Ramsey.]

ALS is a neurodegenerative disease that kills off peripheral and central motor neurons. While other parts of the brain are thought to remain largely unaffected, progressive motor system degeneration can leave fully conscious patients completely paralyzed and unable to communicate, a devastating condition referred to as locked-in syndrome. Many patients with this syndrome use noninvasive eye-tracking devices to communicate with caregivers and loved ones, but glasses and lighting can throw off these devices, leaving people in the dangerous position of being unable to ask for help when they need it. Even in cases where eye trackers suit patients well initially, loss of control over eye movement in late stages of the disease can render those systems useless. 

These problems drove Ramsey and colleagues to design a system that could pick up the slack when eye-tracking falls short. The scientists repurposed implant components already approved for spinal cord stimulation and deep-brain stimulation to create and power a system that picks up signals from the brain and decodes them into a selection from a display of letters on a tablet screen. One by one, the device software automatically highlights rows of letters on the screen. The patient, Hanneke De Bruijne, selects the row she wants when it lights up, and then selects letters from within the row. To make the selection, she tries to move her paralyzed hand, triggering a motor-cortex signal. Signals from this “motor intent” are picked up by two arrays of four electrodes placed on the surface of her motor cortex. Akin to a click on a computer mouse, these signals—or brain clicks as the researchers call them—allow her to create words at a rate of two to three characters per minute. 

Wireless BCI. The devices allows locked-in patients to communicate wherever they go. [Courtesy of Nick Ramsey.]

It’s not fast, noted Leigh Hochberg of Brown University and the Veterans Affairs Medical Center, both in Providence, Rhode Island, but it is wireless. Using other BCI systems studied by Hochberg and colleagues, participants have spelled at an average rate of around 11 characters per minute, with the speediest participant approaching 25. Alas, these devices require patients to be tethered to external equipment via cables that protrude from the brain, and they can only be used when a research technician is there to supervise (see Jarosiewicz, et al., 2015). 

“What Ramsey and colleagues did, which was very smart, was ask what is the simplest need of someone who has nearly completely lost the ability to communicate? That is to indicate a click or a signal that allows reliable control,” said Hochberg. “They’ve got a fully functional system that, after several months of training, somebody can use independently.”

Researchers hope that wireless systems with faster technology will be ready within the next few years. Unlike the older technology used by Ramsey and his colleagues, equipment that gives rise to this kind of speed does not yet have safety approval for use outside of research or without supervision from researchers. Scientists are still fine-tuning these newer systems to ensure that participants can send reliable signals to their devices.

Ramsey’s system could falter if disease progression degrades the motor cortex. In an attempt to head this off, the surgery included a second pair of electrode strips placed over the left prefrontal cortex. This area is activated during mental calculations and is less vulnerable in ALS. Ramsey and his colleagues have already begun to work with the same woman to activate the second strip as a backup system.

Now that the researchers have established a BCI a patient can use autonomously at any time, Ramsey envisions vast improvements on the use of this platform. He hopes other investigators will develop devices with more channels and electrodes that could decode more detailed signals. Motor intent in the form of complex hand gestures might allow patients to use mental sign-language to convey information more quickly through a computer, and in the long run, the group wants to try to decode motor signals that give rise to vocal speech.

The findings provide "further hope that for people who have or are approaching locked-in syndrome, there will be technologies—and in the future more powerful technologies—that will maintain or re-enable communication,” said Hochberg. “It’s a nice moment for the field.”—Lindzi Wessel

Lindzi Wessel is a freelance science writer based in San Jose, California. 

Comments

1. • Leigh Hochberg
     Massachusetts General Hospital and Brown University
   • Posted: 30 Nov 2016

   People with locked-in syndrome—for example, people with advanced ALS—need technologies that can maintain or restore their ability to communicate. This is a basic goal for new technologies called brain-computer interfaces (BCIs). Many researchers, including our own group (www.braingate.org), are developing and testing exciting BCIs that we hope will provide rapid, intuitive, flexible control of communication devices such as tablet computers. In this paper, the Utrecht team wonderfully achieved a purposefully simple yet important goal: a fully implanted system—using available components—that would restore the ability to make a single selection, akin to a "click" or ringing a bell. With that, after considerable training, a woman with ALS was able to control a “serial speller” just by thinking about squeezing her own hand in order to issue a "click" to a computer displaying letters in a series of rows and columns. This is great research, not only in its thoughtful focus on a singular goal, but as another important step toward creating powerful, fully implanted neuroprosthetic systems to help people with paralysis and locked-in syndrome.

   View all comments by Leigh Hochberg

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References

Paper Citations

1. Jarosiewicz B, Sarma AA, Bacher D, Masse NY, Simeral JD, Sorice B, Oakley EM, Blabe C, Pandarinath C, Gilja V, Cash SS, Eskandar EN, Friehs G, Henderson JM, Shenoy KV, Donoghue JP, Hochberg LR. Virtual typing by people with tetraplegia using a self-calibrating intracortical brain-computer interface. Sci Transl Med. 2015 Nov 11;7(313):313ra179. PubMed.

Further Reading

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