BioEd Online

Machines that can be controlled by the mind have moved a step closer to reality. Researchers have trained monkeys to 'think' a cursor around a computer screen to reveal their preferences and goals.

It is hoped the technology will lead to devices that can display the thoughts of paralysed people who are unable to communicate through speech or sign. It could also aid the development of artificial limbs and robots that are operated by the brain alone.

In the past couple of years, researchers have already developed chips that recognise brain signals for movement and convert them into action. Monkeys fitted with the devices have been trained to move cursors around monitors. Such devices translate signals from the brain's motor cortex, the region that directs physical movement.

But now Richard Andersen from the California Institute of Technology, Pasadena, and colleagues have decoded signals from a different region, the parietal cortex, which helps us plan our actions. Their study is published in Science¹.

"It's the difference between thinking 'I want to move my hand to the right' and 'I want to reach for the water'," says Andersen. Devices that tap into the parietal cortex could, in theory, be used to reveal people's intentions and desires.

Flash point

Three monkeys, who had wires inserted into their parietal cortex, were shown a flash of light on a computer screen. After a second of planning, the animals who touched the highlighted spot received a rewarding fruit-juice treat.

Andersen's team recorded the neural activity during the monkeys' thinking phase and identified certain electrical signals that related to planned movement. They then used powerful algorithms to recognise these signals and translate them into the movement of a cursor on the screen. Within a day, the monkeys had learned that thinking about their plan yielded a reward, when the cursor touched the flash of light, and they stopped touching the computer screen.

The team then altered the task to include a variety of reward types, sizes and frequencies. The researchers found they were able to predict what each monkey expected to get in return for thinking about the task.

"It's an exciting study," says John Donoghue, chief scientific officer of Cyberkinetics in Foxborough, Massachusetts, who is developing similar technology for human use. "They know what the monkey is going to do before it even does it."

Computer control

Cyberkinetics recently obtained Food and Drug Administration approval to implant chips in the motor cortex region of five quadriplegic patients to give them mouse control and computer access. Results will be available next year.

Implanting chips in the parietal cortex might yield unexpected side-effects, cautions Donoghue. Suppose you planned to shake your boss's hand, but thought transiently about slapping him in the face. The slap could happen.

Andersen believes that training would soon rule out unwanted responses. And the ideal brain-chip would tap into many different brain regions, coordinating planned actions with instructions for movement.

But there are many hurdles to overcome before neural prosthetics become a reality. Current chips function for up to a year and are connected to a computer by wires. The next generation will need to be longer lasting and wireless.