contributed articles

DoI: 10.1145/1941487.1941506

It has been known since the pioneering work of Hans Berger more than 80 years ago that the brain’s electrical activity can be recorded noninvasively through electrodes on the surface of the scalp. 23 Berger observed that a rhythm of about 10Hz was prominent on the posterior scalp and reactive to light. He called it the alpha rhythm. This and other observations showed the electroencephalogram (EEG) could serve as an index of the gross state of the brain. Despite Berger’s careful work many scientists were initially skeptical, with some suggesting that the EEG might represent some sort of artifact. However, subsequent work demonstrated conclusively that the EEG is indeed produced by brain activity. 23

Electrodes on the surface of the scalp are at some distance from brain tissue, separated from it by the coverings of the brain, skull, subcutaneous tissue, and scalp. As a result, the signal is considerably degraded, and only the synchronized activity of large numbers of neural elements can be detected, limiting the resolution with which brain activity can be monitored. Moreover, scalp electrodes pick up activity from sources other than the brain, including environmental noise (such as 50Hz or 60Hz activity from power lines) and biological noise (such as activity from the heart, skeletal muscles, and eyes). Nevertheless, since the time of Berger, many studies have used the EEG to gain insight into brain function, with many of them using averaging to separate EEG from superimposed electrical noise.

Brain-Computer
Interfaces for
Communication
and Control
BY DennIs J. mCfaRLanD anD Jonathan R. WoLPaW

The brain’s electrical signals enable people
without muscle control to physically interact
with the world.

BraIn aCtIVIty ProDUCes electrical signals detectable on the scalp, on the cortical surface, or within the brain. Brain-computer interfaces (BCIs) translate these signals into outputs that allow users to communicate without participation of peripheral nerves and muscles36 (see Figure 1). Because they do not depend on neuromuscular control, BCIs provide options for communication and control for people with devastating neuromuscular disorders (such as amyotrophic lateral sclerosis, or ALS, brainstem stroke, cerebral palsy, and spinal cord injury). The central purpose of BCI research and development is to enable these users to convey their wishes to caregivers, use word-processing programs and other software, and even control a robotic arm or neuroprosthesis. Speculation has suggested that BCIs could be useful even to people with lesser, or no, motor impairment.

key insights

Brain-computer interfaces provide a new communication-and-control option for individuals for whom conventional methods are ineffective.

Current BCI technology is slow, benefiting only those with the most severe disabilities.

Research may greatly expand the number of people who would benefit from the technology.