A brain-computer interface picks up electrical signals in the patient’s brain and relays them to software she can use to type out words. Using the system, she is able to spell two or three words a minute.

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Researchers have designed a system that lets a patient with late-stage Lou Gehrig’s disease type words using brain signals alone.

The patient, Hanneke De Bruijne, a doctor of internal medicine from the Netherlands, received a diagnosis of amyotrophic lateral sclerosis, also known as ALS or Lou Gehrig’s disease, in 2008. The neurons controlling her voluntary muscles were dying, and eventually she developed a condition called locked-in syndrome. In this state, she is cognitively aware, but nearly all of her voluntary muscles, except for her eyes, are paralyzed, and she has lost the ability to speak.

In 2015, a group of researchers offered an option to help her communicate. Their idea was to surgically implant a brain-computer interface, a system that picks up electrical signals in her brain and relays them to software she can use to type out words.

“It’s like a remote control in the brain,” said Nick Ramsey, a professor of cognitive neuroscience at the University Medical Center Utrecht in the Netherlands and one of the researchers leading the study. On Saturday, the research team reported in The New England Journal of Medicine that De Bruijne independently controlled the computer typing program seven months after surgery. Using the system, she is able to spell two or three words a minute.

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“This is the world’s first totally implanted brain-computer interface system that someone has used in her daily life with some success,” said Dr. Jonathan R. Wolpaw, director of the National Center for Adaptive Neurotechnologies in Albany, N.Y.

The study was partly supported by funds from Medtronic, an international medical technology company, which also provided the components for De Bruijne’s implant. One of the paper’s authors is also a Medtronic employee, though the team notes in its report that “he was not involved in the interpretation of the results.”

The brain-computer interface is not De Bruijne’s only communication tool. For a couple of years, she has used a device that lets her select items on a computer screen by tracking her eye movements. With this system, she can spell five to 10 letters a minute.

The eye tracker has a major drawback, though. Whenever the light levels in her surroundings change, the device must be recalibrated. This makes use outdoors difficult. Worried that she would not be able to alert her caregiver to pressing needs without a communication tool, she avoided going outside, Ramsey said.

“That’s where we found our system really kicks in,” he added. “With it, she feels confident she can spell words for immediate needs, like an itch or saliva building up, or more urgent things, like her respirator giving her problems.”

De Bruijne’s inability to move comes from a disconnect between her brain and muscles. Though she has lost the ability to move, her brain still generates an increase in electricity when she thinks about doing so. The brain-computer interface capitalizes on this.

Electrodes on her motor cortex, the region of her brain that controls voluntary movement, detect small electrical spikes when De Bruijne tries to move her right hand. Specifically, when she thinks about bringing her right thumb and ring finger together, wires transmit a signal to typing software.

The software displays four rows of letters on a tablet, highlighting one row at a time. When it gets to the row De Bruijne wants, she makes a “brain click” by thinking about the hand gesture. Then the program goes along the selected row, left to right. When the correct letter is highlighted, she makes another click. Letter by letter, she spells out her thoughts.

Some researchers have concerns about whether the system’s benefits are worth the risk of surgery.

“Because she can use an eye tracker, the brain-computer interface is not necessary” for De Bruijne to communicate, said Niels Birbaumer, a professor of medical psychology and neurobiology at the University of Tubingen in Germany. Birbaumer added that other, noninvasive brain-computer interfaces had been shown to perform the same function as the communication system from Ramsey’s team.

There are always dangers with surgery, acknowledged John Donoghue, a professor of neuroscience at Brown University and the founding director of the Wyss Center for Bio and Neuroengineering. He added, however, that he thought the risks of this one were “not significantly greater” than those associated with more common procedures, such as deep-brain stimulation to treat Parkinson’s disease, or placement of pacemakers for heart arrhythmias.

Moreover, Donoghue said, Ramsey’s group used a safe, commercial device that the Food and Drug Administration has approved for treating Parkinson’s disease and essential tremor, a neurological disorder that causes involuntary and rhythmic shaking.