A brain-computer interface (BCI), also
known as a brain-machine interface, is a system that allows a person to control
a computer or other electronic device using only his or her brainwaves, with no
movement required.
BCIs can be used for communication, computer access, or control of
devices such as a wheelchair or prosthetic arm, among other applications.
Virtually anything that can be controlled by a computer could, potentially, be
controlled by a BCI. BCI is being examined as a rehabilitation device to help
people re-gain motor skills that are lost from stroke, as well as a prosthetic
device to replace or compensate for motor skills that will never return.
Many people imagine that BCI will
allow them to simply think of a word or phrase and have it appear on the
screen, or control a wheelchair by thinking about where they want to go.
Unfortunately, this is not the case with current BCI technology. There are a
variety of types of BCI systems, and each one works a little differently. Most
BCI spelling systems display a series of letters, either one at a time or by
highlighting letters in a grid. When the letter you want lights up, your brain
wave changes. The computer looks for that change and interprets it as a 'keystroke'.
For example, if you wanted to type the letter A, you would focus on the A and
count each time it flashed, or think “Yes!” when you saw it appear on the
screen. Recognizing the A would trigger a spike in your brain signals, which
would be detected by the BCI system. Usually, each letter must be ‘selected’
multiple times, so typing with a BCI is quite slow. Systems designed to control
a computer cursor often rely on movement imagery. You would imagine squeezing
your right hand to move the cursor to the right, and your left hand to move the
cursor to the left.
A few paralyzed patients could soon be
using a wireless brain-computer interface able to stream their thought commands
as quickly as a home Internet connection. After more than a decade of
engineering work, researchers at Brown University and a Utah company, Blackrock
Microsystems, have commercialized a wireless device that can be attached to a
person’s skull and transmit via radio thought commands collected from a brain
implant. Blackrock says it will seek clearance for the system from the U.S.
Food and Drug Administration, so that the mental remote control can be tested
in volunteers, possibly as soon as this year.
The device was developed by a
consortium, called BrainGate, which is based at Brown and was among the first
to place implants in the brains of paralyzed people and show that electrical
signals emitted by neurons inside the cortex could be recorded, then used to
steer a wheelchair or direct a robotic arm.
A major limit to these provocative
experiments has been that patients can only use the prosthetic with the help of
a crew of laboratory assistants. The brain signals are collected through a
cable screwed into a port on their skull, then fed along wires to a bulky rack
of signal processors. “Using this in the home setting is inconceivable or
impractical when you are tethered to a bunch of electronics,” says Arto
Nurmikko, the Brown professor of engineering who led the design and fabrication
of the wireless system.
The new interface does away with much
of that wiring by processing brain data inside a device about the size of an
automobile gas cap. It is attached to the skull and wired to electrodes inside
the brain. Inside the device is a processor to amplify the faint electrical
spikes emitted by neurons, circuits to digitize the information, and a radio to
beam it a distance of a few meters to a receiver. There, the information is
available as a control signal; say to move a cursor across a computer screen.
The device transmits data out of the
brain at rate of 48 megabits per second, about as fast as a residential
Internet connection, says Nurmikko. It uses about 30 milliwatts of power—a
fraction of what a smartphone uses—and is powered by a battery.
Scientists have prototyped wireless
brain-computer interfaces before, and some simpler transmitters have been sold
for animal research. “But there’s just no such thing as a device that has this
many inputs and spits out megabits and megabits of data. It’s fundamentally a
new kind of device,” says Cindy Chestek, an assistant professor of biomedical
engineering at the University of Michigan.
Although the implant can transmit the
equivalent of about 200 DVDs’ worth of data a day, that’s not much information
compared to what the brain generates in executing even the simplest movement.
Of the billions of neurons in the human cortex, scientists have never directly
measured more than 200 or so simultaneously. “You and I are using our brains as
petabyte machines,” says Nurmikko. “By that standard, 100 megabits per second
is going to look very modest.”
Blackrock has begun selling the
wireless processor, which it calls “Cereplex-W” and costs about $15,000, to
research labs that study primates. Tests in humans could happen quickly, says
Florian Solzbacher, a University of Utah professor who is the owner and
president of Blackrock. The Brown scientists have plans to try it on paralyzed
patients, but haven’t yet done so.
Currently, a half dozen or so
paralyzed people, including some in the late stages of ALS, are taking part in
BrainGate trials using the older technology. In those studies, underway in
Boston and California, the implant that makes contact with the brain is a small
array of needle-like electrodes carved from silicon. Also sold by Blackrock, it
is commonly called the Utah array. To establish a brain-machine interface, that
array is pushed into the tissue of the cerebral motor cortex, where its tips
record the firing patterns from 100 neurons or more at once.
Those tiny blasts of electricity,
scientists have found, can be decoded into a fairly precise readout of what
movement an animal, or a person, is intending. Decoding those signals has
permitted hundreds of monkeys, as well as a growing number of paralyzed
volunteers, to control a computer mouse, or manipulate objects with a robotic
arm, sometimes with surprising dexterity (see “The Thought Experiment”).
But the BrainGate technology will
never turn into actual medicine until it’s greatly simplified and made more
reliable. The head-mounted wireless module is a step toward that goal.
Eventually, scientists say, all the electronics will have to be implanted
completely inside the body, with no wires reaching through the skin, since that
can lead to infections. Last year, the Brown researchers reported testing a
prototype of a fully implanted interface, with the electronics housed inside a
titanium can that can be sealed under the scalp. That device is not yet
commercialized. “If they could put it in
under the skin, then everything you see in the videos could be done at home,”
says Chestek, referring to films of patients using mental control
to move robotic arms. “That wire going through the skin is the most dangerous
part of the system.”
source : http://www.technologyreview.com/
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