How Do We Dream?
Understanding the sleep cycle is the first important part of understanding dreams and how dreams happen. The average human being spends eight hours a day, fifty six hours a week, two hundred twenty-four hours a month, and two thousand, six hundred eighty-eight hours a year sleeping.
Sleep is thought to be made of two basic forms known as slow wave sleep (SWS) and rapid eye movement (REM) sleep. Humans seem to go through four really sharp stages of SWS and then enter REM sleep. The four stages plus REM are mostly happen various times every nightly sleep cycle.
While awake and alert, a human's EEGs (electroencephalograms) contain beta waves at 14-30 Hz, which is relatively high frequency and low voltage activity. When the human is resting and quiet, the EEGs have alpha waves at 8-13 Hz with slightly higher voltage. As humans begin to fall asleep, the EEGs have slower, higher-voltage delta waves, which are a large number of brain neurons (e.g., nerves) firing in unison. The myth is that we "drift off to sleep." The reality is that the onset of sleep is quite sudden. Stage ones sleep involves our breathing slowing, our muscle tone decreasing, and our body relaxing, with slow and low-voltage EEG. Stages 2-4 are notable for the person not awakening by outside push. These stages are marked by increasing frequency of delta waves, and the continued slowing of the body's functions. An exit from the pattern of Stage 1, then 2, 3 and 4 is a sign of physical and/or psychological disorder.
Rapid eye-movement sleep differs from the 4 stages of sleep. During REM sleep, EEG activity of the brain resembles the awake but resting pattern. During REM, there are no delta waves, and the voltage activity is low and fast. To an observer, a human in REM sleep's eyes are beginning to move rapidly beneath the closed lids, as if the human is watching a movie. Also, during REM sleep, there is almost a full clampdown of muscle responses of the body. The body almost seems to be paralyzed.During REM, dream activity is happening.
Dream research has tended to focus to a big degree on dream interpretation and meaning. It may be less interesting to consider how dreams happen. Recent discoveries find that dreams are neurocognitive in origin. To understand dreaming and particularly to understand dream content, it is necessary to better understand dreaming as a developmental cognitive achievement. The word "cognitive" refers to "thinking". "Neuro" refers to "the central nervous system". "Developmental" refers to the changes and maturation that occur from birth. Finally, the neurocognitive system, which is developing and maturing, suggests that there are several forebrain structures which are important to dreaming. Recent research states that the limbic, paralimbic, and associational areas of the forebrain are vital to visual dream imagery. Related research reports that dreaming is a cognitive achievement and in humans develops over the first 8-9 years of life and happens at about the same pace as other developmental areas such as cognition and language. Young children's dreams are very different from adolescent dreams or adult dreams. Until recently, dreams were believed to occur only during REM sleep. Some scientists, known as "brainstorm theorists" believe dreams may occur during Stage 2 Non-Rapid Eye Movement Sleep (NREM). These same scientists believe brainstorm stimulation is as important to dreams as stimulation of the forebrain areas mentioned earlier in this section.
Humans usually enter REM ninety minutes into sleeping and go through Stages 1-4, plus REM, 5-6 times per night. In one year, a human could have on average 1825 dreams of which the typical human remembers only a few of their dreams. REM sleep is thought to be vital for memory and learning. Sleep, particularly REM sleep, is hypothesized to be restorative in nature. If deprived of REM sleep, humans become irritable, anxious, and depressed. When deprived of REM sleep, some humans go into "REM rebound". In other words, REM periods of sleep would occur more often and for a longer period of time than is typical. Drugs and medications frequently interfere with dreaming which suggests that there is a neurochemical relationship to dreams. Recent research is looking at the relationship between the neurochemical dopamine and dream activity. Serotonin may also have a relationship to dreams.