This definition came from the popular reference text, An Universal Etymological English Dictionary, first published by Nathan Bailey in and reprinted through Although adults can suffer from nightmares, they are more typical in children, especially those between the ages of 3 and 6. Nightmares may partially reflect this vulnerability. Dreams are understood to be recent autobiographical episodes that become woven with past memories to create a new memory that can be referenced later, but nightmares are simply dreams that cause a strong but unpleasant emotional response. REM sleep is one example of a quiet period. It is a stage of sleep that is characterized by rapid eye movement, irregular heartbeat, and increased rates of respiration. REM sleep is discontinuous, chunked into four or five periods that together make up about 20 percent of our slumber. It is during these REM episodes that brain structures in the default network exert influence, and it is during REM sleep that vividly recalled dreams occur most often.


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Dreams are hallucinations that occur during certain stages of sleep. Much is known about the role of sleep in regulating our metabolism, blood pressure, brain function, and other aspects of health. When you sleep, your brain is still active, but your thoughts or dreams often make little or no sense. This may be because the emotional centers of the brain trigger dreams, rather than the logical regions. However, there are some popular theories on the role of dreams.
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Dreams are stories and images that our minds create while we sleep. They can be entertaining, fun, romantic, disturbing, frightening, and sometimes bizarre. This article looks at how we dream, what nightmares are, lucid dreams, and why some dreams are difficult to remember where others are more memorable. Most dreams happen during a phase known as rapid eye movement REM sleep. The first REM sleep period usually occurs around 70 to 90 minutes after we fall asleep. During this phase, an amino acid known as glycine is released from the brain stem onto the motor neurons. These motor neurons conduct impulses outward from the brain or spinal cord.
While scientists have been studying dreams for years, the images that appear while we snooze are still incredibly misunderstood. When asleep, our minds are active, creating stories and images that can be either vivid or fleeting; nonsensical or seemingly prophetic; terrifying or absolutely mundane. Why do we dream? We may not have definitive answers, but there are several types of dreams and themes, and different factors that cause these dreams to occur. According to the National Sleep Foundation , we typically dream about four to six times per night. Dreaming happens throughout the night, but our most vivid and often remembered dreams happen during rapid eye movement REM sleep.