OK some more here - there seems to be a lot of exciting activity in this
area.
1.Cf current Scientific American Mind
Putting Thoughts into Action
Eight years ago, when Erik Ramsey
was 16, a car accident triggered
a brain stem stroke that
left him paralyzed. Though fully
conscious, Ramsey was completely paralyzed,
essentially “locked in,” unable to
move or talk. He could communicate only
by moving his eyes up or down, thereby
answering questions with a yes or a no.
Ramsey’s doctors recommended sending him
to a nursing facility. Instead his parents brought
him home. In 2004 they met neurologist Philip
R. Kennedy, chief scientist at Neural Signals in
Duluth, Ga. He offered Ramsey the chance to
take part in an unusual experiment. Surgeons
would implant a high-tech device called a neural
prosthesis into Ramsey’s brain, enabling him to
communicate his thoughts to a computer that
would translate them into spoken words.
Today Ramsey sports a small metal electrode
in his brain. Its thin wires penetrate a fraction of
an inch into his motor cortex, the part of the
brain that controls movement, including the motion
of his vocal muscles. When Ramsey thinks
of saying a sound, the implant captures the electrical
firing of nearby neurons and transmits their
impulses to a computer, which decodes them and
produces the sounds. So far Ramsey can only say
a few simple vowels, but Kennedy believes that
he will recover his full range of speech by 2010.
Ramsey’s neural prosthesis ranks among the
most sophisticated implanted devices that translate
thoughts into actions. Such systems listen to
the brain’s instructions for movement—even
when actual movement is no longer possible
computer or moving a robot. The technology
needed for such implants, including powerful
microprocessors, improved filters and longerlasting
batteries, has advanced rapidly in the
past few years. Funding for such projects has
also grown. The U.S. Department of Defense,
for example, sponsors research in prosthetics for
wounded war veterans.
Only nine people, Ramsey included, have received
brain-implanted prostheses. In the past,
patients have used them to spell words on a computer,
pilot a wheelchair or flex a mechanical
hand. Monkeys have employed them to perform
more complex tasks such as maneuvering mechanical
arms to grab food or controlling a walking
robot on a treadmill [see “Chips in Your
Head,” by Frank W. Ohl and Henning Scheich;
Scientific American Mind, April/May 2007].
[...there's a lot more about the "mechanics" of all this incl.]
But to discover how the
brain actually orchestrates movement, scientists
had to find a way to eavesdrop on the neural signals
in the motor cortex while animals were
awake and moving.
This task proved problematic until investigators
figured out how to stably affix an electrode,
a tiny sliver of conductive wire, to a neuron so
they could register its weak, milliseconds-long
pulses. When animals move, their brains shift
slightly within their skulls, and the motions can
rip an electrode from its anchor in the brain. In
the late 1950s neurologists found that flooding
the space between the skull and the brain with
inert wax or neutral oil buffered the brain the
way Styrofoam peanuts keep a box from moving
inside a larger package. The buffer prevented a
brain from shaking off its implant.
Despite this fix, no one could make sense at
first of the chatter of individual neurons in the motor
cortex. Researchers expected a one-to-one correspondence
between the neurons that fired and
the muscles that contracted during movements.
But when they looked at individual neurons, they
found the neurons would fire when a monkey
moved its arm forward or backward or even when
it kept the arm still.
In the late 1970s neurologist Apostolos Georgopoulos,
now at the U.S. Department of Veterans
Affairs and the University of Minnesota, had
a brainstorm. The spinal cord exerts direct control
over muscles, Georgopoulos realized. Thus,
he supposed that the motor cortex might be directing
movement at a somewhat higher level,
specifying a trajectory rather than the muscles
and joints needed to accomplish a movement.
To test his idea, Georgopoulos developed
something called the center-out task, in which
monkeys learn to move a joystick toward one of
six targets arrayed in a semicircle. “Until then,
all the research designs focused on very simple
movements—forward, stop, back,” he explains.
“In our experiment, the monkey was changing
the position of its shoulder, elbow and wrist
simultaneously.”
No one had looked at such complex motions
before—or analyzed the data the way Georgopoulos
and his colleagues did. Instead of trying
to correlate the firing of particular neurons with
the contractions of certain muscles, he averaged
the responses of small groups of neurons over
thousands of experiments. From that average, he
saw through the noise that neurons produce
when they direct motion, engage in other tasks
or just fire spuriously. Although individual neurons
fired with every movement, each neuron had
a preferred direction: when the monkey moved
the joystick that way, its firing frequency peaked.
Neighboring neurons with similar preferred directions
also became more excited. The closer a
monkey’s arm moved to a neuron’s preferred direction,
the more rapidly it fired; the farther away
the arm moved, the more slowly it fired.
“It’s a sort of democracy,” Georgopoulos explains.
“A given cell will keep voting on the direction
of the movement, whether it’s in the majority
or the minority, but the majority always rules.
And the majority vote is an excellent predictor of
direction.” In this way, the motor cortex sets a
strategy for a movement. It calculates the direction
(and, as Georgopoulos and others later
found, the acceleration) needed for the hand to
reach a target. It then sends the information
to the spinal cord, which implements that strategy
by operating muscles. Those more general
commands from the brain, researchers believed,
might indeed be useful for controlling external
devices.
2. Scientific AMerican Nov.08
The lead article is
"Jacking into the brain"
"How far can science advance brain-machine interface technology?"
[this is more pessimistic..]
If the codes for the sentence “See Spot run”—
or perhaps an entire technical manual—could be
ascertained, it might, in theory, be possible to input
them directly to an electrode array in the
hippocampus (or cortical areas), evoking the
scene in The Matrix in which instructions for
flying a helicopter are downloaded by cell phone.
Artificial hippocampus research postulates a
scenario only slightly more prosaic. “The kinds
of examples [the U.S. Department of Defense]
likes to typically use are coded information for
flying an F-15,” says Berger.
The seeming simplicity of the model of neural
input envisaged by artificial hippocampus-related
studies may raise more questions than it answers.
Would such an implant overwrite existing
memories? Wmould the code for the sentence “See
Spot run” be the same for me as it is for you or,
for that matter, a native Kurdish speaker? Would
the hippocampal codes merge cleanly with other
circuitry that provides the appropriate context,
a semantic framework, for the sentence? Would
“See Spot run” be misinterpreted as a laundry
mishap instead of a trotting dog?
Some neuroscientists think the language of
the brain may not be deciphered until understanding
moves beyond the reading of mere
voltage spikes. “Just getting a lot of signals and
trying to understand what these signals mean
and correlating them with particular behavior
is not going to solve it,” notes Henry Markram,
director of neuroscience and technology at the
Swiss Federal Institute of Technology in Lausanne.
A given input into a neuron or groups of
neurons can produce a particular output—conversion
of sensory inputs to long-term memory
by the hippocampus, for instance—through
many different pathways. “As long as there are
lots of different ways to do it, you’re not even
close,” he says.
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agi
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