A<unk>  of a Girl Before a Sunrise c. 1830–33 by Karl Bryullov (1799–1852) A<unk>  is a succession of images, ideas, emotions, and sensations that usually occur involuntarily in the mind during certain stages of sleep. Humans spend about two hours<unk> ing per night, and each<unk>  lasts around 5 to 20 minutes. The content and function of<unk> s have been topics of scientific, philosophical and religious interest throughout recorded history.<unk>  interpretation, practiced by the Babylonians in the third millennium BCE and even earlier by the ancient Sumerians, figures prominently in religious texts in several traditions, and has played a lead role in psychotherapy. The scientific study of<unk> s is called oneirology. Most modern<unk>  study focuses on the neurophysiology of<unk> s and on proposing and testing hypotheses regarding<unk>  function. It is not known where in the brain<unk> s originate, if there is a single origin for<unk> s or if multiple regions of the brain are involved, or what the purpose of<unk> ing is for the body or mind. The human<unk>  experience and what to make of it have undergone sizable shifts over the course of history. Long ago, according to writings from Mesopotamia and Ancient Egypt,<unk> s dictated post-dream behaviors to an extent sharply reduced in later millennia. These ancient writings about<unk> s highlight visitation<unk> s, where a<unk>  figure, usually a deity or a prominent forebear, commands the<unk> er to take specific actions and may predict future events. The brain activity capable of formulating such<unk> s, rare among literate people in later eras, conforms to the bicameral mentality hypothesized by Julian Jaynes as dominant into the second or first millennium BCE. Framing the<unk>  experience varies across cultures as well as through time.<unk> ing and sleep are intertwined.<unk> s occur mainly in the rapid-eye movement (REM) stage of sleep—when brain activity is high and resembles that of being awake. Because REM sleep is detectable in many species, and because research suggests that all mammals experience REM, linking<unk> s to REM sleep has led to conjectures that animals<unk> . However, humans<unk>  during non-REM sleep, also, and not all REM awakenings elicit<unk>  reports. To be studied, a<unk>  must first be reduced to a verbal report, which is an account of the subject's memory of the<unk> , not the subject's<unk>  experience itself. So,<unk> ing by non-humans is currently unprovable, as is<unk> ing by human fetuses and pre-verbal infants.
Dream
Sniffle
Blood squirt
Powder
Snake
Drustbed
Snuff 
Tablet 