Consciousness

The fact that our brains are electrical is a relatively new discovery. The first article about electrical phenomena in the brains of monkeys and rabbits was published in the British Medical Journal of 1875.
Nearly a half century would pass before the first human EEG (electroencephalogram) was recorded. That distinction would go to German psychiatrist and physiologist Hans Berger who invented the device that would begin the field of electroencephalography. There are 4 basic brain wave frequencies and each correlates with a specific state of consciousness. Like sound frequencies, brain waves are measured in Hz, or cycles per second. In general, the slower the frequency of your brain waves, the more relaxed you feel.