A rare circulatory problem required Emily Wheldon to have her left arm amputated three years ago. Her brain still thinks it's there. "Most days, it just feels like I've got my arm next to me," she says. The perception is so compelling that Wheldon had to train herself not to rely on the missing limb. "When I first had the amputation," she says, "I was trying to put my arm out to stop myself from falling."
But the idea that new technology can decode a person's inner voice is "unsettling," says Nita Farahany, a professor of law and philosophy at Duke University and author of the book: The Battle for Your Brain. "The more we push this research forward, the more transparent our brains become," Farahany says, adding that measures to protect people's mental privacy are lagging behind technology that decodes signals in the brain.
Erin Kunz of Stanford University indicates that brain-computer interfaces (BCIs) can restore speech for paralyzed individuals by decoding signals from the brain's motor cortex, revealing intended speech.