A dream is the experience of images, sounds/voices, words, thoughts or sensations during sleep, with the dreamer usually unable to influence the experience. Dreams are full of (mental) imagery. This imagery ranges from the banal to the surreal; in fact, dreams often provoke artistic and other forms of inspiration. Forms of dreams include the frightening or upsetting nightmare, and erotic dreams with sexual images, erection in males, and nocturnal emission.
The meaning of dreams has interested humanity throughout history. The scientific discipline of dream research is oneirology; dreams have been understood physiologically as a response to stimuli during sleep, psychologically as reflections of the unconscious, and spiritually as messages from God or predictions of the future (oneiromancy).
Most scientists believe that dreams occur in all humans with about equal frequency per amount of sleep; what varies is the ability to recall what is dreamed.
Neurology of dreams
There are many competing theories as to the neurological cause of the dreaming experience. It is not clear in what phase of sleep dreaming takes place, where in the brain dreams originate — if there is such a single location, or even why dreams occur at all.
Dreaming has been associated with rapid eye movement (REM) sleep, a lighter form of sleep that occurs during the latter portion of the sleep cycle. REM sleep is characterized by rapid horizontal eye movements, stimulation of the pons, increased respiratory and heart rate, and temporary paralysis of the body. The nature of the relationship remains an open question, as research has shown that slow-wave sleep impedes dream recall. By way of comparison, dreams (in men) are associated with penis erection about as frequently as with REM sleep.
In line with the theory of REM sleep, the activation synthesis theory developed by Allan Hobson and Robert McCarley states that the brain tries to interpret random impulses from the pons as sensory input. Memory, attention and the other features lacking in a dream state depend on the lack of norepinephrine and serotonin, producing a psychotic state, as well as a lack of orientation in time, place and person.
On the other hand, research by Mark Solms suggests that dreams are generated in the forebrain, and that REM sleep and dreaming are two different brain systems.
Eugen Tarnow suggests that dreams are everpresent excitations of the long term memory system, even during waking life — McCarley also observes that when asked to recall their last thought, subjects often reported somewhat hallucinatory thoughts. The strangeness of dreams is then due to long-term memories being stored in "dream format"; this is reminiscent of the Penfield & Rasmussen’s findings that electrical excitations of the cortex give rise to experiences similar to dreams. During waking life an executive function interprets long term memory consistent with reality checking.
The meaning of dreams has interested humanity throughout history. The scientific discipline of dream research is oneirology; dreams have been understood physiologically as a response to stimuli during sleep, psychologically as reflections of the unconscious, and spiritually as messages from God or predictions of the future (oneiromancy).
Most scientists believe that dreams occur in all humans with about equal frequency per amount of sleep; what varies is the ability to recall what is dreamed.
Neurology of dreams
There are many competing theories as to the neurological cause of the dreaming experience. It is not clear in what phase of sleep dreaming takes place, where in the brain dreams originate — if there is such a single location, or even why dreams occur at all.
Dreaming has been associated with rapid eye movement (REM) sleep, a lighter form of sleep that occurs during the latter portion of the sleep cycle. REM sleep is characterized by rapid horizontal eye movements, stimulation of the pons, increased respiratory and heart rate, and temporary paralysis of the body. The nature of the relationship remains an open question, as research has shown that slow-wave sleep impedes dream recall. By way of comparison, dreams (in men) are associated with penis erection about as frequently as with REM sleep.
In line with the theory of REM sleep, the activation synthesis theory developed by Allan Hobson and Robert McCarley states that the brain tries to interpret random impulses from the pons as sensory input. Memory, attention and the other features lacking in a dream state depend on the lack of norepinephrine and serotonin, producing a psychotic state, as well as a lack of orientation in time, place and person.
On the other hand, research by Mark Solms suggests that dreams are generated in the forebrain, and that REM sleep and dreaming are two different brain systems.
Eugen Tarnow suggests that dreams are everpresent excitations of the long term memory system, even during waking life — McCarley also observes that when asked to recall their last thought, subjects often reported somewhat hallucinatory thoughts. The strangeness of dreams is then due to long-term memories being stored in "dream format"; this is reminiscent of the Penfield & Rasmussen’s findings that electrical excitations of the cortex give rise to experiences similar to dreams. During waking life an executive function interprets long term memory consistent with reality checking.
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