A chip inserted in a young quadriplegic's   brain is already improving his quality of life. Soon the benefits may be more widespread.  A 25-year-old man unable to move from the neck down recently did what many assumed impossible. After a knife attack that had left him paralyzed, all he could move was his head, which he used to push a switch and call for a nurse. And he could turn his wheelchair by blowing into a straw near his face. That was it.  Then last June, a Foxborough (Mass.) company called Cyber Kinetics opened the man's skull and inserted a special chip no larger than a baby aspirin. That insert has given him a few additional and precious abilities. When connected to a special computer via a cable, the chip translates the young man's thoughts into commands that let him move a cursor across a PC screen and open e-mail. He can draw a circle with a computer painting program. And he can use a robotic hook  to perform simple tasks like picking up a candy and sliding it across a table. All he has to do is to think.  Several new studies have begun or been completed in the past year. In fact, more than half of the scientific papers in this field, called brain-to-computer interaction (BCI), have been published in the past two years, notes Jonathan Wolpaw, a research physician at Wadsworth Center, the New York State Health Dept.'s research laboratory.  Brain surgeries   are no longer rare: Thousands of Parkinson's disease patients have had special devices inserted in their brains to ease uncontrollable shaking and other symptoms. The inserts themselves have improved, so the body doesn't reject them as furiously . And significant development has been achieved in software used to interpret the brain's signals and change them into commands understood by computers.  But increased demand for thought technology remains the biggest reason for the field's progress. Today, 4 million Americans live with paralysis according to the Christopher Reeve Paralysis Foundation.  Scientists hope that thought technology will reduce the impact of such disabilities. People with spinal-cord injuries, for example, often lose their ability to walk because the communications network between their brain and their legs has been interrupted. The brain still commands the leg muscles to move, but they don't hear its orders.  Thought technology, scientists hope, will bridge this communications gap. "Our goal is for you to see paralyzed people eating at a restaurant and for you not to know that they are paralyzed," says John Donoghue, founder and chief scientific officer at Cyber Kinetics. What was the young man's trouble after a knife attack?
It was impossible for him to do anything. By no means could he call for a nurse. He could not use his organs under the neck. He was unable to move his head.