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 The system was tested on a 58-year-old woman in the late stages of
amyotrophic lateral sclerosis, or ALS. Unable to speak or move her
muscles, she had to identify the letters by imagining that she was
moving her right hand. Previously, her only method to communicate
was through eye movements and blinks.
"We've built a system that's reliable and autonomous that works at
home without any extra help. There's not a single system that even
comes close to this," chief author Nick Ramsey of the Rudolf Magnus
Brain Center at the University Medical Center Utrecht told Reuters
Health by phone.
Vikash Gilja, a professor of electrical and computer engineering at
the University of California San Diego, who was not connected with
the research, said the system used by the Ramsey team "does not push
the envelope of performance, but that was not the purpose of the
study. The news here is they have developed a system they fitted to
one individual over a long time period and that individual was able
to use it on their own without a lot of technical support."
"Those are major accomplishments," he told Reuters Health by phone.
"It takes us a big step closer to real worldwide-scale clinical
translation of an implanted brain-machine interface."
The hope is that such systems could eventually help others who can't
move but whose brains are still capable of thought and
communication, such as some stroke victims.
The new research, presented November 12 at the annual meeting of the
Society for Neuroscience in San Diego and published online by the
New England Journal of Medicine, was an attempt to find a method
that could be used continuously at home without discomfort or
disfigurement.
Detecting brain signals can be challenging because the brain
generates a lot of electrical noise, and screening out the important
signals can be a challenge.
In this case, four sensor strips for detecting discharges from the
cortex were placed over the hand region of the brain’s left motor
cortex. The surgery was done through four burr holes drilled through
the skull. Each strip had four electrodes. The leads were tunneled
under the skin to an amplifier and transmitter anchored in the
woman's chest. An antenna placed outside the body near the
transmitter picked up the signals and conveyed them to the computer.
Placement of the implanted equipment required two surgeries lasting
a total of just under eight hours.
Testing was done over 28 weeks. The researchers then moved to a
training period where, for example, the woman tried to hit a target
on a video screen by thinking about moving and relaxing her hand.
There was also a key task where the woman tried to accomplish the
equivalent of clicking on a mouse button trying to move her hand for
about 1 second.
When it came time to spell words, letters would be highlighted on a
computer screen and the woman would try to "click" on the one she
wanted.
It took the researchers several months to refine their algorithms to
inhibit unintended brain clicks. Results from eye tracking were used
to confirm what the volunteer typed.
Initially, the woman needed 52 seconds to identify one letter. "The
time required dropped to 33 seconds per letter when word prediction
was used," the researchers reported. At times, she can do up to four
letters per minute.
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"The speed is not that important. It's the certainty with which you
can express yourself," said Ramsey, who explained that the woman has
come to rely on the system when she goes outdoors, where her eye
tracking equipment doesn't always work.
She can spell words directly without help and it gives her the
ability to alert her caregiver that she needs assistance without
relying on the caregiver noticing her eye movements. Such calls for
help can be critical if her ventilator stops working properly or
saliva is building up.
"This is a significant advance in our field," Jonathan Brumberg, an
assistant professor of speech-language-hearing at the University of
Kansas, who was not connected with the work, told Reuters Health in
an email. "It has significant advantages because the patient could
use the device outdoors and with minimal dependency on others for
setting up the device."
The technique poses risks because it requires surgery. In the case
of this woman, side effects included a brief hospitalization for
postsurgical fever, which dropped quickly without treatment. A
feeling of numbness in the skin around the left ear and increased
tiredness also resolved without therapy.
Dublin-based Medtronic developed the implant and associated
equipment, and contributed money to the Dutch government agency that
paid for the research. One of the authors is a Medtronic employee
who helped develop the system.
"By using/modifying existing hardware, the cost of future devices
may be lower than those with completely custom hardware," said
Brumberg. "Also, using existing commercial solutions means that
surgeons will likely be familiar with the components and already
have developed appropriate procedures for their use."
Ramsey said the next step is to streamline the process and test the
system on two more patients before undertaking a large-scale trial.
"I think of it as an achievement that puts implants for
(brain-computer interface) on the map and it allows us develop more
sophisticated devices," he said.
Gilja said such devices are already well under development,
including implants that have 100 electrodes on a 4-square-millimeter
patch. Instead of sitting on the surface of the brain, the
electrodes penetrate a millimeter or so into the brain tissue.
SOURCE: http://bit.ly/2fLANpx The New England Journal of Medicine,
online November 12, 2016.
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