“Researchers have speculated that a fully functioning brain can generate as much as ten watts of electrical power.”*
The electrical activity emanating from the brain is displayed in the form of brainwaves. There are four categories of these brainwaves, ranging from the highest to lower frequency.
Beta waves ~ the brain is aroused and actively engaged in mental activities.
Beta waves are of relatively low amplitude and are the fastest of the four different brainwaves. The frequency of beta waves ranges from 15 to 40 cycles a second.
Beta waves are characteristics of a wide awake / alert state and a strongly engaged mind.
Having all your senses on alert walking down a dark alley at night, making a speech, reading an instruction manual, conscious problem solving or simply having an active conversation are all indications of Beta brainwave activity.
Alpha waves ~ a non-aroused resting state
Alpha brainwaves are slower and higher in amplitude. Their frequency ranges from 9 to 14 cycles per second.
Alpha waves are characteristic of a resting and relaxed mind along with a sense of calmness and well-being.Having worked hard and then sitting down to rest, taking time out reflect on something; doing a light meditation and digesting a big meal are examples of Alpha brainwave activity.
Theta waves ~ the mind is disengaged in an almost dream-like state
Theta brainwaves are typically of even greater amplitude and slower frequency. This frequency range is normally between 5 and 8 cycles a second.
Theta brainwaves indicate a state of mental relaxation such daydreaming or any activity that disengages the active mind such as driving on a freeway and then realising that you can’t recall the last couple of kilometers.
The Theta state is often one of heightened receptivity, flashes of dreamlike imagery, inspiration, long-forgotten memories and great intuition. Theta brain activity makes you receptive to information beyond your normal conscious awareness.
It is also the realm of hypnosis.
Delta waves ~ the sleeping state
Delta brainwaves are of the greatest amplitude and slowest frequency – around a range of 1.5 to 4 cycles per second.
Delta brainwave activity is an indication of restful sleep.
* Ned Herrmann – Scientific American; https://www.scientificamerican.com/article/what-is-the-function-of-t-1997-12-22/