State University, academician of RAEN V.Pimenov, newspaper "Trud", 25.03.2006. made between the brain and spinal cord. In invertebrates, the brain is called the accumulation of nerve cells at the front end of the body.
"The human brain represents 1011 connected and interacting neurons. The following main parts are distinguished in the neuron: body, branches and ends. The body of the neuron is an accumulation of cellular plasma (cytoplasm), which houses the nucleus – the carrier of genetic information and mitochondria – universal energy generators needed to support the cell's activity. The surface of the nucleus is covered by a shell, which is called a membrane. The membrane is the structure in which complex bioelectrical processes take place, ensuring the exchange of the nerve cell with the environment.
The brain works continuously, only in different states it functions differently.
When the state of consciousness is changed (sleep, hibernation, trance, hypnosis, meditation, intoxication, hallucination, delirium, madness, trauma, etc.) the brain continues to work and goes to a different level. It is known that the reflection of brain activity is its bioelectric activity or electroencephalogram.
In modern conditions wide application in experimental and clinical-diagnostic practice has received use of a method of electroencephalography (EEG): "As applied to everyday conditions EEG represents simple enough procedure which does not cause any troubles to the investigated person. A standard number of electrodes are applied to the surface of the head with the help of which potentials from the corresponding areas of the projection of the cortex are recorded and after the preliminary amplification they are recorded in one way or another – on paper, film, tape recorder. Potentials recorded in this way have a value from very weak to 150-
200 мV in a very wide range of frequencies. For the analysis the following frequencies (rhythms) are used more often than others: delta rhythm – 2-4 col/sec, theta rhythm – 4-8, alpha rhythm – 8-13, beta rhythms – 13-30 col/sec. Other indicators are also used in special conditions. The nature of EEG-activity reflects the interaction of different parts of the brain, but expressed in the activity of the cortex of large hemispheres, in the interaction and dynamics of excitation and inhibition processes on its surface.