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EEG (electroencephalography)

Also known as: Electroencephalography, Scalp EEG

Recording the brain's electrical activity with electrodes on the scalp. Safe, cheap and fast, but low in spatial detail.

EEG is the most widely used non-invasive method for recording the brain. It responds within milliseconds but blurs activity across centimetres, because signals spread as they pass through the skull.

It’s used in hospitals (epilepsy, sleep studies), research labs and consumer products such as meditation headbands and focus-tracking headphones. Classic EEG-based BCIs rely on P300, SSVEP or motor imagery signals.

Last updated Sep 30, 2026. Educational content, not medical advice.

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Brain waves (frequency bands)
Rhythmic patterns in brain activity, grouped by frequency: delta, theta, alpha, beta and gamma.
Dry vs. wet electrodes
Wet EEG electrodes use conductive gel for a clean signal; dry electrodes skip the gel for convenience at some cost in quality.
P300
A brain response that appears about 300 ms after you notice something you were looking for. It powers classic EEG "speller" BCIs.
SSVEP
When you look at a light flickering at a fixed rate, your visual cortex echoes that rate. BCIs detect which flicker you're looking at.

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