How Brain-computer Interfaces Work

BCI Drawbacks and Innovators

Two people in Germany use a brain-computer interface to write "how are you?"
Two people in Germany use a brain-computer interface to write "how are you?"
Volker Hartmann/AFP/Getty Images

Although we already understand the basic principles behind BCIs, they don't work perfectly. There are several reasons for this.

  1. The brain is incredibly complex. To say that all thoughts or actions are the result of simple electric signals in the brain is a gross understatement. There are about 100 billion neurons in a human brain [source: Greenfield]. Each neuron is constantly sending and receiving signals through a complex web of connections. There are chemical processes involved as well, which EEGs can't pick up on.
  2. The signal is weak and prone to interference. EEGs measure tiny voltage potentials. Something as simple as the blinking eyelids of the subject can generate much stronger signals. Refinements in EEGs and implants will probably overcome this problem to some extent in the future, but for now, reading brain signals is like listening to a bad phone connection. There's lots of static.
  3. The equipment is less than portable. It's far better than it used to be -- early systems were hardwired to massive mainframe computers. But some BCIs still require a wired connection to the equipment, and those that are wireless require the subject to carry a computer that can weigh around 10 pounds. Like all technology, this will surely become lighter and more wireless in the future.

BCI Innovators

A few companies are pioneers in the field of BCI. Most of them are still in the research stages, though a few products are offered commercially.

  • Neural Signals is developing technology to restore speech to disabled people. An implant in an area of the brain associated with speech (Broca's area) would transmit signals to a computer and then to a speaker. With training, the subject could learn to think each of the 39 phonemes in the English language and reconstruct speech through the computer and speaker [source: Neural Signals].
  • NASA has researched a similar system, although it reads electric signals from the nerves in the mouth and throat area, rather than directly from the brain. They succeeded in performing a Web search by mentally "typing" the term "NASA" into Google [source: New Scientist].
  • Cyberkinetics Neurotechnology Systems is marketing the BrainGate, a neural interface system that allows disabled people to control a wheelchair, robotic prosthesis or computer cursor [source: Cyberkinetics].
  • Japanese researchers have developed a preliminary BCI that allows the user to control their avatar in the online world Second Life [source: Ars Technica].

To learn more about brain-computer interfaces, take a look at the links below.

Related HowStuffWorks Articles

More Great Links


  • CBC News. "Out of the Dark." Jan. 5, 2003.
  • Cheng, Jacqui. "Researchers help users control Second Life avatars via brain activity." ARS Technica, Oct. 15, 2007.
  • Cyberkinetics. "BrainGate Neural Interface System."
  • Greenfield, Susan A. "Brain Story: Unlocking Our Inner World of Emotions, Memories, Ideas and Desires." DK Adult, 2001.
  • McKee, Maggie. "NASA develops 'mind-reading' system." New Scientist, March 2004.
  • Neural Signals. "Speech Restoration Project."
  • Pollack, Peter. "Brain control gives hope to the paralyzed." ARS Technica, July 13, 2006.
  • Walker, Richard. "Secret Worlds: Brain." DK Children, 2002.