Focus

Read Sara Rosenbaum's story: The boy is wired into the computer.

He is 8 years old and has gray cat-eyes. A little blond mohawk sticks up on his head like a strip of uncut grass. His right arm stops just below the elbow.

Its rounded end fits into a clear socket containing two electrodes. From there, two wires lead to the computer.

Boy and machine: a single circuit.

Greg Bauer, the prosthetist, asks him: "Are you ready for the moment of truth?"

"Yes," Jonathan whispers. He's been looking forward to this all week.

On the computer screen is a red bar. When Jonathan flexes one muscle in his elbow, the bar will jump.

Jonathan leans forward, looking down at his arm.

He concentrates.

Nothing happens.

"All ri…