Snap, crackle, pop. I’m listening to a brain talking in a language that seems unintelligible, a chorus of millions of neurons firing, sounding to my ear like the electrical fuzz of a shortwave radio between stations. Then comes a distinctive “pop.” I hear it again: “pop.”

The brain in question belongs to a bearded man sitting in a chair. The victim of a stabbing three and a half years ago, he is paralyzed from the neck down. The ventilator that allows him to breathe is gurgling. Matthew Nagle, a 25-year-old former high-school football star from Weymouth, MA, has a round, titanium pedestal protruding half an inch from his head on the right side near the crown.

On July 4, 2001, Nagle became involved in a melee at Wessagussett Beach in Weymouth. He remembers only that fists began to fly and that a friend was under attack. Someone shouted something about a knife, and Nagle blacked out. Later that night, when his father, a police detective, got a call from the police, he was told that his son would probably die. The 20-centimeter blade had severed the spine in his neck, leaving him paralyzed and on a respirator. Nagle survived, but after years of immobility and tedium, he agreed to take part in a clinical trial to determine whether or not a human could safely manipulate a computer cursor using a brain-computer interface (BCI).

Attached to the pedestal, surgically implanted beneath Nagle’s skull, is an array of electrodes on a chip contiguous to the part of his brain that controls motor ac­tivity. The chip is the size of a baby aspirin: its 100 tiny hair-thin electrodes pick up the electrical signals transmitted by the brain, each electrode capturing signals from a few nearby neurons. As demonstrated in a video I watched late last year, a square, gray plug is screwed onto the pedestal; the plug is attached by wires to a nearby computer. When Nagle’s neurons fire, the impulses are read and decoded by software that can interpret the electrical pops of sets of neurons. The computer reads Nagle’s thoughts—or at least the pops recorded by the electrodes—and deciphers a few simple commands spoken in the electrical language of the brain.

Nagle sits in front of a prosthetic hand. Originally designed for amputees who would con­trol it by twitching muscles in the stumps of their arms, the robotic limb has been hooked up to the computer and will open and shut when Nagle imagines that he is opening and closing his own left hand. Nagle may be paralyzed, but the neurons in his cerebrum that control motor activity are quite healthy.

More here.