To understand ultradian rhythms you need to know a little about brain wave activity in the brain.

 

Brainwaves are the tiny electrical pulses, only a few millionths of a volt, which occur during various types of brain activity such as relaxing, learning, and thinking. Different brainwaves can occur at the same time in different parts of the brain.

 

They are recorded on an electroencephalograph (EEG) by placing electrodes directly onto the scalp.

Brainwaves are categorized according to their frequency, which is shown as hertz (Hz) - the number of times a wave occurs each second.

 

There at least 6 categories of brain waves but we are only going to discuss the main 4 that are related to sleep. If you need more detail then please see the Brainwaves page.

 

Gamma 38 - 90Hz
Beta 14 - 37Hz
SMR 12 - 15Hz
Alpha 8 - 12Hz
Theta 4 - 7Hz
Delta 0.5 - 3Hz

Beta Waves Fully awake and alert.

Alpha Waves Relaxed or daydreaming. Generally associated with right-brain thinking activity.

Theta Waves These waves are associated with flashes of dreamlike imagery, inspiration, and your long-forgotten memories. It is common in deep states of meditation.

Delta Waves Long, slow, undulating waves. Delta is the slowest of all four brain wave frequencies. Most commonly associated with deep sleep, certain frequencies in the Delta range also trigger the release of Human Growth Hormone and so is beneficial for healing and regeneration.