Intermediate
P300
Also known as: P300 speller, Event-related potential, ERP
A brain response that appears about 300 ms after you notice something you were looking for. It powers classic EEG "speller" BCIs.
In a P300 speller, letters flash in a grid. When the letter you want flashes, your brain produces a detectable P300 response. By averaging many flashes, the system works out your choice. It’s slow, at a few characters per minute, but reliable and fully non-invasive.
Last updated Sep 30, 2026. Educational content, not medical advice.