Microchip in brain enables thoughts to control computer
21 July 2006
A multi-institutional team of researchers has found that people with
long-standing, severe paralysis can generate signals in the area of the
brain responsible for voluntary movement and these signals can be detected
by a microchip embedded in the surface of the brain, recorded, routed out of
the brain to a computer and converted into actions — enabling a paralyzed
patient to perform basic tasks.
In the 13 July 2006 issue of Nature, the researchers present the
first published results from the initial participants in a clinical trial of
the BrainGate Neural Interface System, a "neuromotor prosthesis" developed
by Cyberkinetics Neurotechnology Systems, Inc., of Foxborough, Mass.
The first patient, Matthew Nagle, a 25-year-old Massachusetts man with a
severe spinal cord injury, has been paralyzed from the neck down since 2001.
After having the BrainGate sensor implanted on the surface of his brain at
Rhode Island Hospital in June 2004, he learned to control a computer cursor
simply by thinking about moving it.
During 57 sessions, from July 2004 to April 2005, at New England Sinai
Hospital and Rehabilitation Center, Nagle learned to open simulated e-mail,
draw circular shapes using a paint program on the computer and play a simple
video game, "neural Pong," using only his thoughts. He could change the
channel and adjust the volume on a television, even while conversing. He was
ultimately able to open and close the fingers of a prosthetic hand and use a
robotic limb to grasp and move objects. Despite a decline in neural signals
after 6.5 months, Nagle remained an active participant in the trial and
continued to aid the clinical team in producing valuable feedback concerning
the BrainGate technology.
The second patient, a 55-year-old man with a similar injury, had the
sensor implanted by surgeons at the University of Chicago in April 2005 and
was followed by researchers from the Rehabilitation Institute of Chicago and
Cyberkinetics. Although his device initially had electrical problems, these
were repaired and he was able to learn to control the cursor from months
seven through 10 of the trial, until a technical issue caused signal loss at
most electrodes after 11 months.
"The results," said senior author of the paper, John Donoghue, professor
and director of the brain science program at Brown University and chief
scientific officer of Cyberkinetics, "hold promise to one day be able to
activate limb muscles with these brain signals, effectively restoring
brain-to-muscle control via a physical nervous system."
"Our researchers initiated the clinical trial with the hope of being able
to develop a non-obtrusive system that would one day provide more freedom to
those with severe paralysis," said Timothy Surgenor, president and CEO for
Cyberkinetics. "We are eager to expand on this initial proof-of-concept
toward one day providing improved independence and overall quality of life."
The BrainGate System consists of a 4x4 millimetre sensor, about the size
of a baby aspirin, with 100 tiny electrodes, each thinner than a human hair.
The sensor is implanted on the surface of the area of the brain responsible
for voluntary movement, the motor cortex. The electrodes penetrate about 1
mm into the surface of the brain where they pick up electrical signals —
known as neural spiking, the language of the brain — from nearby neurons and
transmit them through thin gold wires to a titanium pedestal that protrudes
about an inch above the patient's scalp. An external cable connects the
pedestal to computers, signal processors and monitors.
Converting digitized intentions into meaningful action, however, is not
simple. Active neurons fire between 20 and 200 times a second and they work
Although scientists have long been able to eavesdrop on individual nerve
cells, before 1996 no one had developed a reliable system for directly
collecting precise data from large groups of brain cells. That year, Donohue
and his post-doctoral student Nicholas Hatsopoulos modified an existing
sensor and used it for the first time to record signals from multiple brain
cells in monkeys.
At the time, Donohue assigned Hatsopoulos — now an assistant professor of
organismal biology and anatomy at the University of Chicago — the task of
creating algorithms to translate the chatter between neurons in the motor
cortex into a language the computer could understand and use to control
other devices. Hatsopoulos and other students in the Donoghue lab were
slowly able to match neuronal signal patterns with specific arm movements.
In 2002, he, Donohue and colleagues at Brown showed that monkeys could learn
to control the cursor without moving a muscle.
Meanwhile, in order to move into human trials, Donohue, Hatsopoulos,
Gerhard Friehs and Mijail Serruya, all then at Brown, formed Cyberkinetics,
which was incorporated in 2001. In 2002, they merged with Bionics, makers of
the sensor, raised $5 million, and applied to the FDA for approval to
conduct a pilot clinical trial. The trial began in 2004. So far, four
patients have enrolled.
For each trial patient, training sessions begin soon after the sensor is
inserted. The volunteer is asked to imagine moving one hand as if he were
controlling the computer mouse. The researchers study the data and build
filters to convert patterns of neural spikes into two- dimensional commands.
"Training patients to move things with their minds is different with each
patient," said Maryam Saleh, who worked with the first two patients as a
Cyberkinetics technician and is now a doctoral student in Hatsopoulos's
The current BrainGate System is still in its infancy and is far from
perfect. It is bulky and cumbersome. The quality of the signal can vary from
patient to patient and from day to day. A great deal of work remains to be
done to extend the longevity and reliability of the sensor. Patient two
never developed as much control as Nagle, and even Nagle's level of control,
the authors note, "is considerably less than that of an able-bodied person
using a manually controlled computer cursor."
Despite remarkable progress, "this isn't being done for the patient's
benefit," said University of Chicago neurosurgeon Richard Penn, who
implanted the sensor in the second patient. "It's being done for mankind's
"Most people involved in this study think of themselves as pioneers,"
said Saleh. "They see the prospects for future applications. That's why they
Nevertheless, Penn added, "this is the strangest, most interesting
surgery I've ever done. Not the technical stuff, but the data that we get
from the neurons firing in different patterns when you're thinking in
different ways. And seeing it is only the beginning."
The system is constantly being improved. Next steps include faster and
more precise algorithms to help the computer keep pace with the neuronal
inputs, and a more portable wireless system. The researchers are also
looking at new applications, such as enabling the brain-computer combo to
control a wheelchair or other gadgets that will restore some control and
freedom to patients with severe paralysis.
At the American Spinal Cord Injury Association meeting in June, David
Chen, medical director of the spinal cord injury rehabilitation program at
the Rehabilitation Institute of Chicago, presented preliminary results from
a third participant in the trial. This patient, who is unable to speak
because of a brainstem stroke, can control a cursor with significantly
greater stability than the first two. He can stop cursor movement at will,
"click" on icons and type messages using assistive software.
"We believe these advances could ultimately enable a paralyzed person to
control communication devices, medical devices, computer-controlled
robotics, wheel chairs — and even their own limbs," said Cyberkinetics's
"As a physician," said Harvard's Leigh R. Hochberg, lead author of the
Nature paper and a principal investigator in this pilot trial, "I do
whatever I can to optimize the recovery of patients with paralyzing
disorders such as stroke, spinal cord injury or neuromuscular disease. The
available assistive technologies, however, provide neither sufficient
independence nor mobility.
"Thanks to the generosity and pioneering spirit of our initial trial
participants, who have volunteered without expecting to derive any personal
benefit, important progress is being made in developing a real-time
neuromotor prosthesis," Hochberg said. "Though much work remains to be done,
hopefully one day, I’ll be able to say: 'We have a technology that will
allow you to move again.'"
University of Chicago Hospitals medical news
article, Mind over matter (PDF):