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February
15 , 2005 —
In "Cybersenses," Alan Alda explores how modern technology
is helping to repair the communication breakdown between sensory
systems and the brain. People who need cochlear or retinal
implants have problems with their afferent connections —
the nerves that transmit information from the outside world
to the brain. Scientists are also looking at ways to mend
the opposite problem where broken efferent connections can't
transfer information from the brain to the body because the
communication path is impaired. Here are some of the different
types of technologies that are being developed to help bridge
this communication gap.
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It's another one of those nights. You're lying in bed awake
trying to remember some random fact like the name of an actor.
You could turn on the computer and Google the answer, but
that would require getting out of bed. Wouldn't it be nice
to be able to directly connect your brain to the internet
and perform the entire search in your head? But that's just
science fiction. Or is it?
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The
brain's motor cortex sends out instructions to the body,
while the somatosensory cortex receives inputs about
the environment.
Credit: "Huntington's Outreach Project for Education,
at Stanford"
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In
recent years, the brain-computer interface (BCI) field has
ramped up research. An increasing number of groups are studying
the instructions the brain sends out to the body, developing
ways to read those instructions, and translating them into
outputs in the external world. Experiments have demonstrated
that monkeys with chips implanted in their brains can operate
a robotic arm purely by thought. These chips read the electric
outputs of neurons that are intended for the monkey's real
arm, and transmit those neural signals to a mechanical arm
through a computer. Over time the monkey learns that it can
bypass moving its own arm in order to mentally control the
robotic arm. The applications for this type of technology
are exciting, especially for those with physical disabilities
such as quadriplegia and Amyotrophic Lateral Sclerosis (ALS).
The
Human Circuitry
The
wiring of the human brain to the rest of the body consists
of a complex system weaving together the activity of millions
of neural cells for a single action. To move your arm, for
instance, a population of neurons in the motor cortex, the
part of the brain that controls movement, sends neural signals
along many nerve circuits to the arm. These signals contain
all the instructions on what the arm should do.
People
who have those "wires" cut or damaged, such as those with
spinal cord injuries, can no longer get those neural signals
from the brain to their targets. BCI research is leading toward
technologies that can bridge that neural communication gap.
Brain
Feed
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In
BrainGate technology, tiny electrodes implanted in
the brain pick up neural signals and pass the message
on to a computer.
Credit: Cyberkinetics Neurotechnology Systems, Inc.
(Click
to enlarge)
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Researchers
have taken several different approaches to fix this connection.
One is to plug the brain directly into a computer. Cyberkinetics,
a biotech company in Foxboro, Massachusetts, has developed
a device called BrainGate, which does exactly that. The device
consists of a tiny chip containing 100 microscopic electrodes
that is surgically implanted in the brain's motor cortex.
The whole apparatus is the size of a baby aspirin. The chip
can read signals from the motor cortex, send that information
to a computer via connected wires, and translate it to control
the movement of a computer cursor or a robotic arm. According
to Dr. John Donaghue of Cyberkinetics, there is practically
no training required to use BrainGate because the signals
read by a chip implanted, for example, in the area of the
motor cortex for arm movement, are the same signals that would
be sent to the real arm. A user with an implanted chip can
immediately begin to move a cursor with thought alone. However,
because movement carries a variety of information such as
velocity, direction, and acceleration, there are many neurons
involved in controlling that movement. BrainGate is only reading
signals from an extremely small sample of those cells and,
therefore, only receiving a fraction of the instructions.
Without all of the information, the initial control of a robotic
hand may not be as smooth as the natural movement of a real
hand. But with practice, the user can refine those movements
using signals from only that sample of cells. 
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This
type of robotic hand can be manipulated by thoughts.
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