Sleep and Stages of Sleep

body when it was itself not physical. He said there was a dualism between the realm of thought and the realm of the body and believed that the brain played a role.

Sigmund Freud addressed consciousness. He said there were three levels of awareness. These are the conscious, the preconscious, and the unconscious. They relate to his ideas of the id, the ego, and the superego. The conscious is the alert state, with awareness of the internal and external environment. The preconscious are where memories are stored and retrieved. The unconscious are things outside the awareness that cannot be retrieved or are felt to be unacceptable. They still have the capacity to influence behavior.

Modern theorists have studied consciousness. There is a theory that consciousness is related to a person s developmental level. Social psychologists see consciousness as related to cultural influences with language playing a big role in the experience of reality. Neurobiologists see consciousness as purely a function of the biology of the brain.

SLEEP AND STAGES OF SLEEP

People spend a third of their lives just sleeping. Sleep varies greatly in the animal kingdom, with little sleep gotten by amphibians and dolphins and certain death to rats who die from sleep deprivation. Sleep involves decreased physical activity and reduced awareness. Sleep rebound happens when people fall asleep faster after a period of deprivation.

There are multiple brain areas that work together to facilitate and regulate sleep. These include the pons, the hypothalamus, and the thalamus. The thalamus and the hypothalamus together help control slow-wave sleep, while the pons participates in REM or rapid eye movement sleep.

There are hormones associated with sleep. These include melatonin, growth hormone, luteinizing hormone (LH), and follicle stimulating hormone (FSH). It is during sleep that FSH and LH are secreted so sleep seems to be important in the generation of normal sexual function. Growth hormone is released by the pituitary gland in response to sleep.

No one knows exactly why people sleep but there are theories. It is probably partly related to evolutionary selection. Sleep might be important in reducing energy needs by the body. It may have also once been adaptive to the presence of predators that usually come out at night. Sleep lowers stress levels, helps to maintain weight, improves motor coordination, enhances mood, and improves memory and cognition. Memories are formed during sleep, particularly slow-wave sleep. Creativity increases with sufficient sleep.

There are several stages of sleep. These can be demonstrated showing different brain wave patterns. The two main divisions of sleep are REM sleep and non-REM sleep. REM sleep is seen with eye fluttering and is usually when dreaming occurs. Non-REM sleep has four stages.

Stage 1 sleep is the transition between sleep and wakefulness. There are alpha and theta waves during this phase. The person is very relaxed and easily awakened. Stage 2 sleep is deeper and is associated with sleep spindles that are crucial for learning and memory. K-complexes are seen in stage-2 sleep, which can be triggered by the external environment.

Stages 3 and 4 of sleep are related and are together referred to as slow-wave sleep or delta sleep because of the presence of delta brain waves. The heart rate and respiratory rate will diminish significantly and it is most difficult to awaken a person from this stage of sleep. It takes the presence of delta waves in these stages to feel the most rested sleep.

REM sleep reveals electroencephalograhic (EEG) waves that are most similar to the waking state. This is when dreaming most occurs. There is paralysis of the muscles, except for those that are necessary for respirations and circulation. There is such a thing as REM rebound, in which there is more REM sleep after a period of lost REM sleep. REM sleep is related to emotional regulation and the processing of certain emotions. There are no negative impacts from a lack of REM sleep and its suppression may help depression.

Sigmund Freud was interested in dream interpretation; he felt that dreams represented a way to have access to the unconscious state. There was manifest content, which is the