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Brain-Computer Interfaces for Communication and Control
Published: Jun 21, 2007


For many years, people have speculated on how electrophysiological measures of brain function might provide a new non-muscular channel for sending messages and commands to the external world * a brain-computer interface (BCI).

With the advent of powerful low-cost computer equipment and recognition of the needs and potentials of people with disabilities, the productive BCI research programs have arisen over the past decade. These programs concentrate on developing new augmentative communication and control technology for those with severe neuromuscular disorders, such as amyotrophic lateral sclerosis, brainstem stroke and spinal cord injury, so that they can express their wishes to caregivers, operate simple word processing programs, or even control a neuroprosthesis.

With BCI, a person can communicate with or control the external world without using the brain’s normal output pathways of peripheral nerves and muscles. Messages and commands are expressed by electrophysiological signals from the brain, and not by muscle contractions. Present-day BCIs determine the wishes of the user from a variety of different signal features. They are translated in real-time into commands that operate a computer display or other device. Successful operation requires that the user have control over the signal features and that the BCI correctly derive the user’s intentions from them. BCI operation depends on the interaction of two adaptive controllers, the user, who must maintain close correlation between his or her intentions and these signal features, and the BCI, which must translate them into device commands that accomplish the user’s intentions. The user and the BCI system need to adapt to each other both initially and continually so as to ensure stable performance.

Present-day BCIs provide information transfer rates of up to 25 bits/min. With this relatively limited capacity, they can provide basic communication and control functions (e.g., environmental controls, simple word processing) to those with the severe neuromuscular disabilities. They might also support basic control of a neuroprosthesis that provides hand-grasp to those with mid-level cervical spinal cord injuries. More complex BCI applications useful to a larger population of users depend on achievement of higher information transfer rates.

BCI systems might provide an important new communication and control option for those with motor disabilities. They might also give to those without disabilities a supplementary control channel or a control channel useful in special circumstances.

Source: Jonathan R. Wolpaw, Laboratory of Nervous System Disorders, Wadsworth Center
http://www.axistive.com/brain-comput...d-control.html