These are small electrical currents that can be measured by the number of vibrations or waves per second.
Brain waves are expressed in Herz (Hz) and are measured by an EEG. They can be divided into five different categories based on the number of Hz:
- Gamma waves: 38 to 80 Hz. These waves occur during strong mental activities such as studying and solving problems.
- Beta waves: 14 to 38 Hz. Beta waves occur when you are active and allow you to concentrate. When there is an excess of these types of waves, you experience stress. While sleeping or meditating, the amount of beta waves decreases.
- Alpha waves: 8 to 14 Hz. These waves are active when you are relaxed, for example while sleeping or daydreaming.
- Theta waves: 4 to 8 Hz. Theta waves are present when you are creative. They also often occur during REM sleep, the phase of sleep where you dream. You need this sleep phase to process the events of the day. People who do not sleep well therefore have problems processing the experiences of the day.
- Delta waves: 0.5 to 4 Hz. During deep sleep, a phase before and after REM sleep, the delta waves are active. They are associated with the body’s recovery stage in which new cells are produced.