Nightmare

The New YorK Times
By NATALIE ANGIER
Published: October 23, 2007

In the Dreamscape of Nightmares, Clues to Why We Dream at All By all evidence, outrageously bad dreams are a universal human experience. Sometimes the dreams are scary enough to jolt the slumberer awake, in which case they meet the formal definition of nightmares — bad dreams that wake you up.

Nightmare content also shifts over time and across cultures. A young man in 21st-century America might not mind the occasional bawdy dream, but for St. Augustine, the fourth-century Christian philosopher, “sexual dreams were nightmares”.

When slipping into REM sleep, “the whole brain changes.” “Neurochemically, it’s like the Fourth of July,”

Most sleep scientists are convinced that dreaming serves an essential, possibly evolutionarily adaptive, purpose; "dreaming served to create what they call “fear extinction memories,” the brain’s way of scrambling, detoxifying and finally discarding old fearful memories, the better to move on and make synaptic space for any novel threats that may show up at the door. “The brain learns quickly what to be afraid of,” . “But if there isn’t a check on the process, we’d fear things in adulthood we feared in childhood.”
Ordinary bad dreams rarely recapitulate unpleasant events from real life but instead cannibalize them for props and spare parts, and through that reinvention, Dr. Nielsen explained, the fears are defanged. “A bad dream that doesn’t lead to awakening is successful in dealing with intense emotion,” he said. “It’s disturbing, but there is some kind of resolution to the extent we don’t wake up.”
By this scenario, nightmares, in allowing you to escape prematurely, represent a failure of the “fear extinction” system. “Bad dreams are functional, nightmares dysfunctional,” he said.
If you feel yourself falling, spread your arms out and learn how to fly.