Brainwaves
Delta, theta, alpha, beta, gamma: what these frequencies actually measure, and why they show up everywhere — from deep sleep to meditation.
The electroencephalogram (EEG) measures the brain’s surface electrical activity. Depending on the state, that activity oscillates at different dominant rhythms — the famous “brainwaves”.
The frequency map
- Delta (0.5–4 Hz): deep sleep, recovery.
- Theta (4–8 Hz): drowsiness, hypnagogia, deep meditation, memory.
- Alpha (8–12 Hz): relaxed wakefulness, eyes closed.
- Beta (12–30 Hz): active wakefulness, focus, sometimes stress.
- Gamma (30 Hz and up): integration, notably observed in experienced meditators.
Read these numbers with care
These bands describe correlations, not magic switches: you do not “shift into theta” like changing gears. But they provide a precious common language linking sleep, meditation and tools like binaural beats.