Through a clinical collaboration between Caltech, Keck Medicine of USC, and Rancho Los Amigos National Rehabilitation Center, a man paralyzed from the neck down can use a robotic arm to perform a fluid hand-shaking gesture, drink a beverage, and even play "rock, paper, scissors." The neural prosthetic device is implanted in a region of the brain where intentions are made.

Previous neural prosthetics have been placed in the motor cortext, the brain's movement center. By implanting neuroprosthetics in the posterior parietal cortex (PPC), a part of the brain that controls not the movement directly but rather the intent to move, Caltech researchers have developed a way to produce more natural and fluid motions.

In April 2013, the device was surgically implanted in the PPC of Erik G. Sorto, a man paralyzed after suffering a gunshot wound when he was 21. Sorto has since been training with Caltech researchers and staff at Rancho Los Amigos to control a computer cursor and a robotic arm with his mind.

Charles Y. Liu, professor of neurological surgery and neurology at the Keck School of Medicine of USC and biomedical engineering at USC, and his team implanted a pair of small electrode arrays in two parts of the posterior parietal cortex, one that controls reach and another that controls grasp.

Each 4-by-4 millimeter array contains 96 active electrodes that, in turn, each record the activity of single neurons in the PPC. The arrays are connected by a cable to a system of computers that process the signals, to decode the brain’s intent and control output devices, such as a computer cursor and a robotic arm.