New Way to Control Prosthetic Device with Brain Signals

Another milestone has been achieved in the quest to create prosthetic devices operated by brain activity. Californian neuroscientists report on success in getting monkeys to move the cursor on a computer screen by merely thinking about a goal they would like to achieve, and assigning a value to the goal.09/07/2003

The research California Institute of Technology neuroscientists Sam Musallam, Brian Corneil, Bradley Greger, Hans Scherberger, and Richard Andersen holds significant promise for neural prosthetic devices. Andersen explains that the "goal signals" from the brain will permit paralyzed patients to operate computers, robots, motorized wheelchairs--and perhaps someday even automobiles. The "value signals" complement the goal signals by allowing the paralyzed patients' preferences and motivations to be monitored continuously.

This new approach departs from earlier work on the neural control of prosthetic devices in that most previous results have relied on signals from the motor cortex of the brain used for controlling the limb. Andersen says the new study demonstrates that higher-level signals, also referred to as cognitive signals, emanating from the posterior parietal cortex and the high-level premotor cortex (both involved in higher brain functions related to movement planning), can be decoded for control of prosthetic devices.

The study involved three monkeys that were each trained to operate a computer cursor by merely "thinking about it," Andersen explains. Combined with the goal task, the monkey is also told what reward to expect for correctly performing the task. The researchers are able to predict what each monkey expects to get if he thinks about the task in the correct way. The monkey's expectation of the value of the reward provides a signal that can be employed in the control of neural prosthetics.

This type of signal processing may have great value in the operation of prosthetic devices because, once the patient's goals are decoded, then the devices' computational system can perform the lower-level calculations needed to run the devices.

Since the brain signals are high-level and abstract, they are versatile and can be used to operate a number of devices. As for the value signals, Andersen says these might be useful in the continuous monitoring of the patients to know their preferences and moods much more effectively than currently possible.

"The result suggests that a large variety of cognitive signals could be interpreted, which could lead, for instance, to voice devices that operate by the patients' merely thinking about the words they want to speak”, Andersen concludes.

- Find out more on: www.caltech.edu

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