Consciousness is the highest integrative function of the human brain. It is consciousness reflecting reality in all its manifestations that underlies the process of cognition of the surrounding world and one's personality as well as the purposeful, active regulation of the interaction among a human, nature and society. A human is simultaneously the subject of society and its member, and they are a member of a community of people actively transforming nature and society. The laws of the nature and development of society are revealed unconsciously, spontaneously, a human on the contrary, comprehends them consciously and applies them to casual situations and for their existence. In this regard, consciousness is a necessary quality that helps a human to adapt to the environment.
The prefix "со" ("so") in the Russian word "сознание" ("soznaniye") (for "consciousness" in English), in opinion of S.S. Korsakoff (1901), reflects the set of knowledge possessed by an individual; in this respect, A.A. Megrabyan (1972) assumes that such semantics of the term also means that knowledge is achieved by an individual together with people and society. One should note that consciousness is not only a knowledge of the environment and oneself, it includes thinking processes, memory, the emotional-volitional sphere, and orientation of an individual; such orientation manifests their attitude to the environment.
K. Jaspers (1913), a prominent historian, existentialist, philosopher and psychiatrist, has grounded the basic criteria for understanding and diagnosing clinical types of disorder (disintegration), or clouding of consciousness. Speaking about the common indicators of clouding of consciousness formulated by K. Jaspers, it is important to bear in mind that only the simultaneous presence of all the indicators in the disease's clinical picture is a necessity and is sufficient criterion for any diagnosis. Indeed, individual indicators can be found in other psychopathological syndromes that are not related to syndromes of clouding of consciousness. The persuasiveness of generalisation of consciousness clouding main indicators, given by K. Jaspers is beyond question as these provisions have been confirmed by the practice of several generations of research psychiatrists