A young adult man with closely cropped dark brown hair sits in a wheelchair in a dimly lit room, facing a computer screen on which a simple phrase is typed out: “How are you today?” Underneath the question on the screen, three dots appear—similar to the ones messaging apps use to signal that your conversation partner is composing a response—and flash with anticipation. One by one, new words materialize: “I am very good.” At first glance, this brief conversation doesn’t seem particularly special, but the man’s situation is anything but ordinary. On top of his head is a small box, about one inch square in size, connected to a circular portal in his skull about the size of a nickel.
Protruding from the box is a thin black cable. The man, who goes by the nickname Pancho, is paralyzed and unable to speak, but a BCI records brain waves from the part of his cortex that is responsible for generating speech, the vocal motor cortex, and translates them into words on the computer screen. In 2003, at the age of twenty, Pancho experienced a devastating brainstem stroke while recovering from a car accident and major surgery.
After a week in a coma, he woke up paralyzed and unable to speak. The connections between his brain and his vocal muscles disrupted by the stroke, he couldn’t even make sounds as he cried. For years, Pancho’s main method of verbal communication relied on a pointer attached to a baseball cap.
He’d use the limited mobility that remained in his neck to move his head forward and down to tap keys on a computer screen, one at a time. Spelling out words like this enabled him to communicate, albeit at the agonizingly slow pace of five words per minute. But in recent years, a groundbreaking brain implant and a research collaboration with scientists at the University of California, San Francisco has been, for Pancho, “very much like getting a second chance to talk again.” The lab of neurosurgeon and scientist Edward Chang builds technologies that help paralyzed people like Pancho recover their ability to communicate by translating their brain activity into language.
The Chang lab’s speech prosthesis project has incorporated many of the elements of the neuroscience tool kit we’ve discussed in other chapters; for example, like other BCIs, it uses precise e-phys recordings from specific parts of the brain that are important for generating behaviors. Before working with Pancho, Chang and his colleagues spent over a decade studying the basic neurobiology of speech in the human brain using similar recordings from non-paralyzed subjects. In brain-mapping studies that recalled Wilder Penfield’s pioneering work, his team steadily uncovered fundamental principles of how speech is represented by neural activity.
Pancho’s implant, a delicate array of electrodes spread over a flat, flexible rectangular device like a business card, is placed on the surface of his vocal motor cortex, which governs speech production. Wire-thin cables protruding from the implant exit Pancho’s skull through the coin-sized opening. These electrode arrays, which contain anywhere from 128 to just over 200 separate electrodes, record the collective activity of many neurons and send the neural waveforms to a computer for analysis.
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