"On the Cutting Edge" front page
THE DEVICE, which would look rather like the head of a toothbrush
— a mount with electrodes as its bristles — would work similarly to a
cellular phone, sending signals to other electrodes implanted in the
patient’s nerves or muscles.
A new understanding of brain circuitry is allowing scientist to
develop the device, said Dr. Richard Andersen of the California Institute
of Technology.
Similar prostheses are already being used to help people who are
deaf, he said. By stimulating different auditory nerves, the smart brains
are helping patients to lip-read more easily.
The new device for paraplegics is growing out of Andersen’s work on
the physical organization of the brain.
Using imaging scans called MRIs to record blood flow in the brain of
monkeys, Andersen pinpointed the part of the brain that codes for
intentions. In contrast to previous beliefs, he found that movement and the
intention to perform a movement are controlled by different parts of the
brain.
To make sure human brains work the same way, his team then tried the
experiment on themselves, hooking themselves up to brain tracing devices
and MRIs. When they only moved their eyes, they were able to detect an eye
movement area — signaling intention — in one particular region of the
brain, he said. Similarly, when they reached their arms out, they found an
area in the brain that corresponded to the intention to move their arm.
That’s what gave them the idea for the brain prostheses for people
with spinal cord injuries, Andersen said at a scientific meeting here.
As the California researcher envisions it, a 6mm by 3mm array of
electrodes about the width of human hair would be implanted under the
brain’s surface. The wires, which are attached to a transmitter, would send
radio-type signals to other electrodes implanted in the muscles and nerves
of the arms or legs. Normally, the spinal cord carries such signals from
the brain to the rest of the body.
“We’re only talking about crude movements,” Andersen said, but it’s
better than any system that has been developed to date.
Animal tests are about to begin, with human testing just years off.
“We’re over all the major hurdles,” Andersen said, explaining that the time
is needed for development.
The prostheses are being developed in conjunction with the
Huntington Memorial Research Institute in Pasadena.