itting stone still under a skull cap fitted with a couple dozen electrodes, American scientist Peter Brunner stares at a laptop computer. Without so much as moving a nostril hair, he suddenly begins to compose a message — letter by letter — on a giant screen overhead.

“B-O-N-J-O-U-R” he writes with the power of his mind, much to the amazement of the largely French audience of scientists and curious onlookers gathered at the four-day European Research and Innovation Exhibition in Paris, which opened Thursday.

Brunner and two colleagues from the state-financed Wadsworth Center in Albany, New York were demonstrating a “brain computer interface (BCI),” an astounding technology which digitalizes brain signals emitted as electrical impulses — picked up by the electrodes — to convey intent.

While no spoons were bent, this was definitely mind over matter.

Without recourse to nerves or muscles, BCI “can provide communication and control to people who are totally paralyzed” and unable to unable to speak or move, explains researcher Theresa Sellers, also from Wadsworth.

Dr. Sellers estimates there are some 100 million potential users of BCI technology worldwide, including 16 million sufferers of cerebral palsy, a degenerative brain disease, and at least five million victims of spinal cord injury. Another 10 million people have been totally paralyzed by brainstem strokes, she said.

Scientists have been experimenting with ways to translate thought directly into action for nearly two decades, but BCI has only recently begun to move out of the laboratory and into the daily lives of those trapped inside bodies that no longer respond to their will.

Possible applications extend beyond the written word into physical movement — it is only a matter of time, Sellers says, before the same technology is used to operate motorized wheel chairs. “We can do already. But it is a complex problem, and for now it would be unsafe,” she says.

The frightful condition of being “locked in” came into the public eye in the late 1990s, when French journalist and Elle Magazine editor Jean-Dominique Bauby, after suffering a massive stroke, painstakingly “dictated” a beautiful and moving memoir by blinking his left eyelid.

“The Diving Bell and the Butterfly,” published two days before he died, became an international bestseller.

Had BCI technology been available to him, Bauby would almost certainly have been able to write his book unassisted, and in a fraction of the time.

The Wadsworth system, one of several that detects electroencephalographic (EEG) activity, is based on an algorithm that analyzes the brain waves and identifies peaks in activity that correspond to particular mental efforts.

As Dr. Brunner concentrates on the “B” of “bonjour” in a keyboard-like grid of letters and symbols taking up half the screen, a computer randomly highlights lines of characters in rapid succession.

Each time the row — vertical or horizontal — containing the letter “B” is illuminated, Brunner’s brain emits a slightly stronger signal. It takes the computer about 15 seconds to figure out what letter he is looking at. The system is doubly adaptive, with both the software and the person using it becoming more efficient over time.

“It may not sound very practical, but for someone who is paralyzed it can make all the difference in the world,” says Sellers.

Indeed, for at least one 48-year old neurobiologist in the United States stricken with amyotrophic lateral sclerosis — an invariably fatal degenerative disease that attacks nerve cells — the Wadsworth BCI technology has make it possible not only to communicate but to continue working, even though he can no longer even move his eyes.

“He writes grant proposals, sends e-mails and can use the keyboard of a computer at home,” Sellers said of the man, whom she did not identify in order to protect his privacy.

He even wrote a message for the exhibition in Paris, which Sellers projected onto a screen.

“To Altran,” he began, referring to the French innovation consulting firm that sponsors an annual competition for public service innovation, won in 2005 by the head of the Wadworth Center, Jonathan Wolpaw.

“I am a neuroscientist who couldn’t work without BCI,” the message read, typo and all. “I am writing this with my EEG courtesy of the Wadsworth Center Brain-Computer Interface Research Program.”