Sensors pick up brain activity, software decodes what it means and an output device acts on it, such as a cursor, a robotic arm or a speech synthesizer. Non-invasive systems use electrodes on the scalp, called EEG, and are safe but give weak signals. Invasive systems place electrodes on or inside the brain and give far richer signals but need surgery. Most work aims to help people with paralysis, ALS or stroke communicate and move.
BCIs remain mostly in research and early clinical trials. Signals change over time, so systems need frequent recalibration, hardware can fail or provoke scarring, and equipment is costly and complex. Privacy, consent and who owns neural data raise open questions.
The BrainGate project implanted a sensor array in a paralyzed man, Matthew Nagle, in 2004, and he controlled a computer cursor with his thoughts. In 2023 two research teams, at Stanford and at the University of California, San Francisco, reported systems that turn brain signals into speech at rates of about 62 and 78 words per minute.
When you read about a BCI, check whether it was tested in people, how many took part, how long it worked and how accurate it was outside the lab.