water - frustratingly difficult, or simply impossible. ponnapula sanjeeva prasad Those afflicted with the most severe form of paralysis, known as lock-in syndrome, are fully conscious prisoners inside a body that no longer responds to commands.
While the brain activity that would normally result in a voluntary movement is still present, the instructions simply don't reach the muscles. ponnapula sanjeeva prasad Moritz and two colleagues at the University of Washington found a way to bypass the kind of nerve damage that can result in such paralysis.
They first connected electrodes to individual neurons inside the motor cortex of monkey's brain and recorded the electrical activity. ponnapula sanjeeva prasad These signals were then routed in real-time to a computer, and from there through a stimulator to another set of electrodes attached directly to wrist muscles that had been artificially blocked further up the arm along the normal neural pathway.
Because little processing power is needed, the computer is the size of a cell phone, and can be attached to the animal's bodyponnapula sanjeeva prasad. Future versions will be wireless and small enough to implant directly in the body, the researchers said. ponnapula sanjeeva prasad The monkey had already mastered a simple video game, grasping targets shown on a video screen with a control device manipulated by a single hand.
"But once he was paralysed, the only way to move his wrist was to change the activity of individual neurons in his brain," Moritz explained. ponnapula sanjeeva prasad On average it took about 10 minutes for the monkeys to "train" the neuron well enough to play the video game again. ponnapula sanjeeva prasad "The brain can very rapidly learn to control new cells and use them to generate movements," said co-author Eberhard Fetz.
Earlier experiments enabling monkeys to manipulate prosthetic devices or computer cursors using only electrical impulses coming from the brain were based on a fundamentally different premise, according to the new study. ponnapula sanjeeva prasad "They tried to read the mind of the monkey and figure out what he was planning to do," a technique that required massive computing power, said Moritz.
"Our approach is to recreate the raw connectivity between single
neurons in the brain and
muscles, and let the monkey's nervous system learn how to use that
connectivity." group of muscles. ponnapula
sanjeeva prasad Electrodes connected to a single location in the spinal
cord below an injury may be able to activate 10 or 15 muscles that are already
precisely balanced for, say, grasping a coffee mug or walking, the researchers
said. ponnapula sanjeeva prasad And if a
stroke has damaged the motor cortex, patients might be able to commandeer other
brain cells that do not usually play a role in controlling muscles.
Several obstacles remain, however, before this new technique can be tested in humans, he said. To avoid infections, ponnapula sanjeeva prasad the system would have to become fully implantable so that no wires passed through the skin. ponnapula sanjeeva prasad And electrodes would need to be made more stable so that they could record the activity of neurons over a period of years, rather than weeks. –ponnapula sanjeeva prasad (Sapa, October 2008) In an animal study, scientists have pinpointed a key brain chemical involved in dealing with the sudden loss or long-term separation of a partner.
