Degrees of Freedom is an amazing article by Raffi Khatchadourian from The New Yorker covering some of neuroscience history and what it took to enable paralyzed people move robotic arms with their brains.

For eighteen years, Jan Scheuermann has been paralyzed from the neck down. She is six feet tall, and she spends all day and all night in a sophisticated, battery-powered wheelchair that cradles her—half sitting, half reclining—from head to toe.

In the following days, her performance improved further. As the researchers were correcting their algorithms, her brain was correcting its responses to them. She began to refer to Hector as “my arm,” a slip of the tongue that soon became habit. “It happened without me realizing it,” she told me. “I just said, ‘Let me see if I can get my arm to do that.’ Or, ‘My arm’s not going that way.’ ”