What are brain-computer interfaces?

Brain-computer interfaces read patterns in brain activity and translate them into commands for a device.

These devices read brain signals to control computers, prosthetics, or wheelchairs. Companies are testing implants that help paralyzed patients type and move—raising big medical hopes and big ethical questions.

Why it matters

For someone who cannot move or speak — after a spinal injury or with a condition like ALS — a reliable link between brain and computer is not a gadget. It is communication, independence, and control over their surroundings. That medical need is why most BCI research starts with patients who have the fewest other options.

How a BCI works, step by step

1. Sensors listen. Electrodes either sit on the scalp (a cap or headset) or, in implanted systems, rest in or on the brain itself, close to the neurons.
2. The system records patterns. When you imagine moving your hand or focus on a letter, groups of neurons fire in a recognizable pattern.
3. Software decodes the pattern. Trained on examples from that person, it translates “they are imagining a right-hand move” into a command.
4. The device acts: a cursor moves, a letter appears, a robotic arm or wheelchair responds.
5. The person practices. BCIs are a skill on both sides — the software learns the user while the user learns to produce clearer signals.
6. Implants hear the clearest signals but require surgery; headsets avoid surgery but hear a muffled version through the skull. Every BCI design trades between those two facts.