artifact (signal artifact)

An artifact is non-brain junk that sneaks into a brain recording and masquerades as real signal. The sensors do not only pick up neurons; they also catch electrical activity from elsewhere — and that intruding clutter is the artifact. It is the static on the radio that has nothing to do with the song.

Common culprits are very ordinary: an eye blink sends a big sweep across nearby electrodes, clenched or moving muscles add a buzzing mess, the heartbeat leaves a steady pulse, head or cable movement causes jumps, and the building's power lines hum a constant 50 or 60 cycles per second into everything. Because brain signals are so faint, these intruders are often much larger than the activity you actually want.

Dealing with artifacts is a huge part of practical brain–computer interface work. Engineers design recordings to avoid them, then detect and remove or filter them out afterward, so the genuine neural signal underneath can be read. A system that ignores artifacts will happily mistake a blink or a twitch for a brain command.