What is Consciousness? This question has been subject of debate since the time of Descartes.
Simply put, consciousness can be considered a level of awareness, both internal and external. (Subjective or Objective) Let’s look at 3 of the most common states of consciousness.
1) Waking state.
2) Dreaming State
3) Dreamless Sleep
These 3 states of consciousness are pretty self-explanatory and familiar to any mentally healthy functioning human being. From here, there are many other states of consciousness that very, depending on the source material from which you may be investigating.
One theory on what creates various states of consciousness is based on brainwave patterns. There are 4 basic ranges of brainwave frequencies.
Beta Waves (14-30 Hz)
Beta waves are the most common in everyday waking state consciousness. Chances are, as you are reading this, you are creating primarily Beta waves. This frequency is often associated with concentration and cognition. Beta waves at the higher levels are associated with anxiety and overwhelm.
Alpha Waves (8-13.9 Hz)
Alpha waves are common while in a state of relaxation, light trance, or meditation. Serotonin levels are increased, and is often associated with the experience of pre-sleep, and pre-waking.
Theta Waves (4-7.9 Hz)
Theta waves occur prominently in REM sleep cycles. They are also common in deep meditation and trance states.
Delta Waves (.1-3.9 Hz)
Dreamless sleep. HGH released in the brain. Non-physical awareness.
The multiple frequencies occurring in any human at anytime create a mandala like pattern that informs the state of consciousness in the moment. There are many kinds of biofeedback machines that can detect or even entrain particular brain wave states through light or sound waves. (I have been using binaural beats in my meditation practice for years)
There are also 2 other types of brain wave frequencies discovered in the last century, Gamma Waves, and Mu Waves. Most of research has yet to be conclusive on these frequencies. (See Ken Wilber change his Brainwave patterns Here)