Our brains are made up of billions of brain cells called neurons. Neurons use electricity to communicate with each other. The combination of millions of neurons sending signals at once produces an enormous amount of electrical activity in our brains, which can be detected using sensitive medical equipment such as an EEG (Electroencephalograph), measuring electricity levels over areas of the scalp. Because of its cyclic, wave-like nature, the combination of electrical activity of the brain is commonly called a brainwave pattern.
Brainwave speed is measured in Hertz (cycles per second) and can be categorized into five main groups – Gamma, Beta, Alpha, Theta and Delta.1 For each category we have presented broadly descriptions, because in practice things are far more complex than that, and brainwaves reflect many different aspects when they occur in different locations in the brain and different circumstances.
12Hz to 27Hz
Wide awake. This is generally the mental state most people are in during the day and most of their waking lives. Usually, this state in itself is uneventful, but don’t underestimate its importance. Many people lack sufficient beta activity, which can cause mental or emotional disorders such as depression and ADD.7 8 and insomnia. And low SMR production (a sub-range of beta at 12-15hz) may be related to insomnia.9 Stimulating beta activity can improve emotional stability, energy levels, attentiveness and concentration.10 11 12
8Hz to 12Hz
Awake but relaxed and not processing much information. When you get up in the morning and just before sleep, you are naturally in this state. When you close your eyes your brain automatically starts producing more alpha waves.
Many studies monitoring the EEG activity of experienced meditators have revealed strong increases in alpha activity.13 Alpha activity has also been connected to the ability to recall memories, lessened discomfort and pain, and reductions in stress and anxiety.14 15 16 17
0.2Hz to 3Hz
Deep, dreamless sleep. Delta is the slowest band of brainwaves. When your dominant brainwave is delta, your body is healing itself and “resetting” its internal clocks.20 You do not dream in this state and are completely unconscious.
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