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DIGITAL PEOPLE

lyzed man, who then learned to control a computer without moving a muscle.

Much of Kennedys work began at Emory University, and con- tinues at his company Neural Signals. A visit to the company mostly reveals cluttered electronic workbenches where Kennedy and his col- leagues work out how to process the signals elicited from implanted electrodes. But the heart of Kennedys achievement is the unique neurotrophicelectrode that he developed, so small that it is not apparent on his workbench. Its design keeps it well anchored in the brain without undesirable motion or loss of electrical contact, prob- lems that can plague conventional electrodes.The device consists of two fine gold wires attached to a tiny hollow glass cone the size of a pen tip.The inside of the cone is coated with nerve tissue, taken from another part of the patients body, which encourages the growth of nerve cells.When the cone is inserted into the brain, neurons grow through both its open ends to hold it firmly in place as they connect to the electrodes.The signals from the wires are sent first to an ampli- fier and then to a computer.

Kennedys great achievement has a second part, in clinical set- tings. He has implanted his electrode in patients who were severely paralyzed due to various causes including amyotrophic lateral sclerosis (ALS or Lou Gehrigs disease), the condition that afflicts the British physicist Stephen Hawking. Among these patients was Johnny Ray, a Vietnam War veteran who was left locked-inat age 53 by a stroke; that is, he was left with full cognitive function but no bodily control except for limited face and neck motion.In 1998,Kennedy implanted two electrodes into Rays motor cortex (the part of the brain where movement commands originate as its neurons fire), specifically in the area devoted to moving the hands.

Ray sent signals through the electrodes to control a cursor he could watch on a computer screen, but achieving that control was not an overnight process. In initial training, Ray was asked to imagine he was moving his hands to activate the electrodes, but this strategy did not produce consistent results. After some months, however, he was able to move the cursor reliably, and these movements were correlated

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