Advances in cognitive neurosci- ence and brain-imaging technologies give us the unprecedented ability to interface directly with brain activity. These technologies let us monitor the physical processes in the brain that correspond with certain forms of thought. Driven by society's growing recognition of the needs of people with physical disabilities, researchers have begun using these technologies to build brain-computer interfaces (BCIs)communication systems that don't depend on the brain's normal output pathways of peripheral nerves and muscles. In BCIs, users explicitly manipulate their brain activity instead of motor movements to produce signals that control computers or communication devices. This research has extremely high impact, especially for disabled individuals who can't otherwise physically communicate.