What distinguishes the conscious-unconscious polarity is the degree of accessibility or awareness of behavior of ones own introspection, that is, the range with which we can refer exactly to our activity. Unconscious, in the term “unconscious mental processes” mean all mental processes except those discrete aspects of brief phase which enter awareness as they occur. The unconscious reminds us that human objectivity and freedom certain limitations. “Conscious” is a subjective term without, as yet,(i) interpretation in terms of physiological structure, or(ii) explanation of its function. Conscious, expresses the normal idea of awareness that the individual has of himself or of things as they are present. In short, consciousness involves a) monitoring ourselves and our environment so that percepts, memories, and thoughts are represented in awareness; and b) controlling ourselves and our environment so that we are able to terminate the behavioral and cognitive activities. And subconscious, comprises all that area of psychic experience which is not present t the actual consciousness of the individual and cannot be evoked at leisure.
We spend about one-third of our lives in the altered state of consciousness called sleep. But first, what is sleep? Sleep is a state during which brain activity differs from that during the waking state. Sleep is an active mental process that does not involve a “turning off” of the brain as scientists once believed. Although sleep is a natural state, we knew little about sleep patterns until the sleep studies on the 1960s and 1970s. These studies revealed that we alternate between two different stages of sleep known as non-rapid eye movement (NREM) sleep and the rapid eye movement (REM) sleep, during which most dreaming takes place. Each type of sleep exhibits different physiological features. There are at least four different stages of sleep have been identified, and each state is associated with characteristic brain waves. A fifth stage of sleep, the period during which dreaming takes place. The first stage of sleep is called the light sleep of the falling asleep stage- a very short stage, usually occurring a few minutes after bed time. The person is easy to wake and may not realize he has been asleep if awakened. Stage two of sleep is characterized by sudden bursts of fast wave activity from the front regions of the head (called sleep spindles). The third stage is somewhat similar to stage two and is also marked by large, slow changes in voltage. The sleeper is hard to wake and unresponsive to stimuli. Stage four is the deepest level of sleep, characterized by the largest, slowest waves (1-3 cycles per second), which are called delta waves. Delta sleep occurs in 15-or-20 minute segments (interspersed with lighter stages) during the first half of the night.