"Researchers have long dreamed of devising prosthetic devices that could be operated by paralyzed people using brain signals alone."

A report by Musallam et al. in the 9 July 2004 Science now marks a big step toward realizing that goal. Past studies have shown that information from neurons signaling physical movement can be used to control prosthetic devices, but the new study shows that higher-level "cognitive" neurons can also provide the necessary information. The researchers used monkeys with electrodes implanted into the parietal reach region PRR) of their brains, which is involved in planning -- but not executing -- future arm movements. Monkeys were trained to reach toward an icon in one of eight locations on a computer screen while a computer program tried to interpret the patterns of neural activity during the task. Once the neuronal "code" for the reaching task was deciphered, the program began using the code to determine the direction the monkeys were planning to reach during trials in which the monkeys thought about reaching but did not actually do so. The monkeys showed improved performance at this task over time, thereby honing the brain signals sent by the PRR and enabling the computer to accurately predict the direction of the reach nearly 70% of the time. The researchers simultaneously recorded the reward preferences of the monkeys and further showed that when the monkeys knew that accurately thinking about the requested movement would yield a preferred reward, the cells in the PRR became more responsive to the direction of the planned movement. As noted in an accompanying news story by I. Wickelgren, the new work suggests that goal-oriented signals can be used to operate computers, prosthetics, and other "smart" devices.