Why Do We Have Nightmares
Dreams that help you deal productively with emotions, memories, and other information may seem very helpful. The occasional nightmare is considered a dream thats simply more frightening or upsetting. Nightmares tend to be caused by stress, anxiety, or sometimes as a reaction to certain medications.
However, if you have nightmares frequently, you could have a sleeping disorder. Regularly occurring scary dreams can be labeled a sleeping disorder if the nightmares:
- cause you to be anxious about going to sleep
- lead to frequent disruptions of your sleep
- bring about other sleeping or psychological problems
Many people experience occasional nightmares throughout their lives. However, the American Sleep Association estimates only about 5 percent of the population experiences persistent nightmares as a sleeping disorder.
Some factors that affect us when were awake can also influence our dreams.
Dream Recall And Well
One study looked at whether dream recall and dream content would reflect the social relationships of the person who is dreaming.
College student volunteers on measures of attachment, dream recall, dream content, and other psychological measures.
Participants who were classified as high on an insecure attachment scale were significantly more likely to:
- report a dream
- experience intense images that contextualize strong emotions in their dreams
Older volunteers whose attachment style was classed as preoccupied were significantly more likely to:
- report a dream
- report dreams with a higher mean number of words
Dream recall was lowest for the avoidant subjects and highest for the preoccupied subjects.
Everyone dreams, although we may not remember our dreams. At different times of life or during different experiencs, our dreams might change.
How Are Dreams Created
One study suggests that dreams stem more from your imagination than from perception .
But there is so much more to discover. We know much but not all of whats going on physiologically during dreams. We have far more to learn about whats going on psychologically.
For example, we know that nightmares are a manifestation of tension for people with PTSD, because they recur around their traumatic experience. For others, are dreams related to good moods or bad moods?
We cant answer this easily because we have not found a good way to study dreams in people. Memories of dreams fade quickly after you wake up, and its difficult to correlate brain scans with patients reports of their dreams.
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Awake Brain Makes Model Of The World By Guessing
“Even when we take information from real sensory stimuli directly into the cell roots in an awake state, the information is very difficult to interpret and basically completely incomprehensible to the brain, Storm says.
But the pyramidal neurons can recognize patterns in the signals by comparing them with patterns stored in memory. This is how the brain can guess what we perceive, like recognizing a cup, a house or a human being, says Storm.
This is how the brain builds up an internal model of the outer world, by assembling and interpreting the sensory signals from the sensory organs, he says.
The brain thus uses previous experience to interpret what we see, smell, taste or hear, he says.
In an awake state, the cerebral cortex receives most of its information through the roots of the pyramidal cells.
But when we sleep, this information flow to the roots is turned almost all the way off, Storm says.
Box 1can Reports Be Trusted To Accurately Convey Internal Experiences In Sleep
Do dream reports obtained by awakening a sleeping subject accurately convey subjective experiences in sleep? At one extreme, we could be fully conscious throughout sleep but remember dreams well, little, or not at all depending on the brain state when we are awakened. Indeed, we know that dreaming often goes unreported some people claim they rarely dream, but systematic awakenings in sleep labs have revealed that we greatly underestimate how often and how much we are conscious during sleep. On the other hand, neurological patients who report loss of dreaming are no more likely to have memory disorders than those who report dreaming, suggesting that lack of dream reports indeed reflects lack of experience rather than changes in memory alone. Further studies may illuminate this issue since, for example, memory-related regions in the medial temporal lobe are highly active in REM sleep .
Functional neuroanatomy of human REM sleep: a meta-analysis of PET results
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Dreams: What They Mean
One thing is certain: if you sleep, you dream. Neurologists and other experts have long been trying to ascertain the reason and purpose for our dreams. They generate theories about how dreams work:
for instance, they suspect that when we dream our brain mixes new information with existing experiences and stores these creating a learning effect. Other theories suggest that dreaming instils practical skills in the brain that may be useful later on. Another theory implies that dangerous situations are simulated in dreams to ensure we are better prepared for these when awake. In terms of evolutionary biology, this would mean that our ancestors fought natural foes in dreams, while we in the 21st century imagine precarious situations at work.
But another theory is that, ultimately, our dreams could simply be random products of our brain synapses and have absolutely no systematic meaning.
Where Do Dreams Come From
Dreamland might not require so much imagination after all.
ByShaunacy Ferro | Published Sep 13, 2013 9:28 PM
When we close our eyes and drift off to sleep, something in our mind spins us fanciful tales of teeth falling out, bouncing around in giant marshmallows in the sky, failing midterms in classes weve never taken, taking a walk in the park down the street thats also a spaceship. Common as they are, theres not a lot of definitive science on how we dream.
Are dreams the work of the imagination, or the work of some reflex in the brain? A team of French researchers suggest at its most basic, dreaming is generated by the brainstem, the part of the brain that connects to the spinal cord and plays a role in regulating sleepa bottom-up process rather than a result of the brains higher functions.
The study looked at patients with auto-activation deficit, a syndrome characterized by extreme apathy. People with auto-activation deficit lose the ability to spontaneously activate any cognitive or emotional processes. They report that they dont have any thoughts at all, called mental emptiness. They often sit quietly in the same place all day without speaking or moving. If someone prompts them, they can answer questions and recall memories, but left to their own devices, their minds remain blank. So if these patients dont have spontaneous thoughts, do they dream?
The full study was published in Brain this week.
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Dreams & Whats Happening In The Brain
Dreaming is such a fascinating topic because everyone dreams , but the experience of dreaming can vary from person to person. We do know that most dreams last about 5-20 minutes, and you can have multiple dreams in a night. The variability is in the experience of dreaming, recollection, and intensity.
Some people remember their dreams vividly, and others do not. Some have the same dream over and over while others rarely repeat a dream. Some remember only a handful of dreams in their lifetime but others can recall dreams nightly. Some are lucid dreamers, and most of us are not. Others dream in color, while some dream in black and white .
Muses EEG Spectogram image above shows the intensity of brainwave activity over time. High-intensity regions are indicated by tones of red, yellow, green, and low-intensity regions are indicated by tones of blue.
Up until the advent of the electroencephalogram , researchers were unable to access or measure electrical activity that occurs in the brain during all states of consciousness. Previously, it was believed that sleep was a fully resting state, when in fact there are varying levels of brain activity that occur during different stages of sleep. Our brain fluctuates between four main types of waves depending on the level of wakefulness or relaxation .
Men And Women Dream Differently
Researchers have found some differences between men and women when it comes to the content of their dreams. In several studies, men reported dreaming about weapons significantly more often than women did, while women dreamed about references to clothing more often than men.
Another study showed that men’s dreams tend to have more aggressive content and physical activity, while women’s dreams contain more rejection and exclusion, as well as more conversation than physical activity.
Women tend to have slightly longer dreams that feature more characters. When it comes to the characters that typically appear in dreams, men dream about other men twice as often as they do about women, while women tend to dream about both sexes equally.
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Research Shows That Dreaming Is Not Just A Byproduct Of Sleep But Serves Its Own Important Functions In Our Well
We often hear stories of people whove learned from their dreams or been inspired by them. Think of Paul McCartneys story of how his hit song Yesterday came to him in a dream or of Mendeleevs dream-inspired construction of the periodic table of elements.
But, while many of us may feel that our dreams have special meaning or a useful purpose, science has been more skeptical of that claim. Instead of being harbingers of creativity or some kind of message from our unconscious, some scientists have considered dreaming to be an unintended consequence of sleepa byproduct of evolution without benefit.
Sleep itself is a different story. Scientists have known for a while now that shorter sleep is tied to dangerous diseases, like heart disease and stroke. There is mounting evidence that sleep deprivation leads to a higher risk of obesity and Alzheimers disease. Large population studies reflect a saddening truththe shorter your sleep, the shorter your life. Not only that, sleep helps us to hold onto our memories and to learn facts and skills faster, making it important for everyone including infants, students, athletes, pilots, and doctors.
Much of this I outline in my new book, Why We Sleep: Unlocking the Power of Sleep and Dreams, which summarizes the many findings we have about sleep and its function in our lives.
But what about dreaming? Does it also have a purpose?
Box 3lesion Studies Of Dreaming
The primary source on neuropsychology of dreaming is a study by Solms who examined 361 neurological patients and asked them in detail about their dreaming. Overall, lesion studies indicate that dreaming depends on specific forebrain regions rather than on the brainstem REM sleep generator. In most cases, global cessation of dreaming follows damage in or near the temporo-parieto-occipital junction , more often unilaterally than bilaterally. This region supports various cognitive processes that are essential for mental imagery. Accordingly, patients with such damage typically show a parallel decline in waking visuo-spatial abilities. These results strongly suggest that mental imagery is the cognitive ability most related to dreaming .
Apart from global cessation of dreaming, more restricted lesions produce the cessation of visual dreaming , or the disruption of particular visual dimensions in dreams. For example, lesions in specific regions that underlie visual perception of color or motion are associated with corresponding deficits in dreaming. In general, it seems that lesions leading to impairments in waking have parallel deficits in dreaming.
Despite these remarkable similarities, what makes dream consciousness so fascinating are the ways in which it differs from our waking experience. Some of these phenomenological differences are accompanied by consistent neurophysiological differences.
Reduced voluntary control and volition
Altered mnemonic processes
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The Brain In Norem Sleep
Serotonergic nuclei of the raphe of the brainstem, as well as the nucleus of the solitary fasciculus, the thalamic reticular nucleus, the anterior hypothalamus and nuclei of the preoptic area and the basal forebrain, are decisively involved in the genesis of slow sleep or NREM. Serotonergic neurons block motor activity and the intensity of sensory input.
Other inhibitory neurotransmitters include adenosine and g-aminobutyric acid , as well as various peptides.
The progressive deactivation of the activating reticular cholinergic system allows the appearance of recurrent thalamocortical rhythms that give rise to the sleep spindles and to the slowing of the EEG.
Memory Types And Dreaming
Two types of memory can form the basis of a dream.
- autobiographical memories, or long-lasting memories about the self
- episodic memories, which are memories about specific episodes or events
A study exploring different types of memory within dream content among 32 participants the following:
- One dream contained an episodic memory.
- Most dreams in the study contained low to moderate incorporations of autobiographical memory features.
Researchers suggest that memories of personal experiences are experienced fragmentarily and selectively during dreaming. The purpose may be to integrate these memories into the long-lasting autobiographical memory.
A hypothesis stating that dreams reflect waking-life experiences is supported by studies investigating the dreams of psychiatric patients and patients with sleep disorders. In short, their daytime symptoms and problems are reflected in their dreams.
In 1900, Freud described a category of dreams known as biographical dreams. These reflect the historical experience of being an infant without the typical defensive function. Many authors agree that some traumatic dreams perform a function of recovery.
One paper that the main aspect of traumatic dreams is to communicate an experience that the dreamer has in the dream but does not understand. This can help an individual reconstruct and come to terms with past trauma.
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Lower Brain Causes Rem Sleep
The oldest part of the brain, shared by all vertebrates, is the brain stem. In 1977, Allan Hobson and R McCarley discovered that electrochemical pulses from the brain stem create the stage of sleep in which most dreams occur. Known as REM, which stands for rapid eye movement, this stage of sleep guides the paralysis of all voluntary muscle groups, except for the eyes. Scientists believe these brain pulses from the pons region of the brain stem may create the seemingly random shifts in dream scenery for which dreams are so well known.
- The oldest part of the brain, shared by all vertebrates, is the brain stem.
- In 1977, Allan Hobson and R McCarley discovered that electrochemical pulses from the brain stem create the stage of sleep in which most dreams occur.
Why Do Dreams Seem So Bizarre
This may have to do with neurotransmitters, or brain chemicals. Some are more pronounced, while others are suppressed, during REM sleep.
Acetylcholine is more prominent, as is dopamine . Dopamine may help to give dreams their surreal quality.
The relationship between space and time also changes when we dream. Time may seem to last forever or pass by very quickly.
Meanwhile, REM sleep suppresses the neurotransmitters that usually keep us awake: histamine, serotonin and norepinephrine. Thus, were less conscious of our environment.
Some researchers suspect the thalamus closes when we dream.
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Similarities Between Dreaming And Waking
In order to gain insight into the phenomenology and neural basis of dreams, it is useful to consider both similarities and differences between waking consciousness and dreaming consciousness, and to relate these differences to changes in brain activity and organization. Perhaps the most striking feature of conscious experiences in sleep is how altogether similar the inner world of dreams is to the real world of wakefulness. Indeed, at times the dreamer may be uncertain whether he is awake or asleep. Certainly, dreams are not created in a vacuum but closely reflect the organization and functions of our brain.
In most dreams, perceptual modalities and submodalities that dominate in wakefulness are heavily represented. Dreams are highly visual, in full color, rich in shapes, full of movement, and incorporate typical wakefulness categories such as people, faces, places, objects, and animals. Dreams also contain sounds , and more rarely tactile percepts, smells and tastes, as well as pleasure and pain. Experiences in typical dreams have a clear sensory character and are not mere thoughts or abstractions.
Negative Dreams Are More Common
Over a period of more than 40 years, researcher Calvin S. Hall, PhD, collected over 50,000 dream accounts from college students. These reports were made available to the public during the 1990s by Hall’s student William Domhoff. The dream accounts revealed that many emotions are experienced during dreams.
There are several factors that can impact the emotional content of dreams, including anxiety, stress, and certain medications. One study found that external stimuli, including good and bad smells, can play a role in positive and negative dreams.
The most common emotion experienced in dreams is anxiety, and negative emotions, in general, are much more common than positive ones.
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Left And Right Side Of The Brain
The right and left hemispheres of the brain seem to contribute in different ways to a dream formation.
Researchers of one study concluded that the left hemisphere seems to provide dream origin while the right hemisphere provides dream vividness, figurativeness and affective activation level.
A study of adolescents aged 10 to 17 years found that those who were left-handed were more likely to experience lucid dreams and to remember dreams within other dreams.
Higher Brain Makes Sense Of It All
Why dont we realize when dreaming that monsters, ghosts and goblins are not real? In 2002, co-author Allen Braun of the National Institutes of Health published positron emission tomography, or PET, data from the brain scans of dreaming patients clearly showing how the higher brain is largely offline during dreaming sleep. Specifically, the prefrontal cortex that generates language, logic and critical thinking is taking an electrochemical nap while we run away from our nightmare goblins. However, some critical thinking still occurs in dreams, evidenced by the way we create new outcomes in dreams by trying to work around the weird plot changes and bizarre visual imagery.
An exception to the lack of executive functioning in REM sleep may be lucid dreaming, which is when the dreamer knows he is dreaming 3. Validated in the laboratory by Stanford psychophysiologist Stephen LaBerge, lucid dreaming is marked by conscious choices, active thinking and logical reasoning in the dream 3. This claim is strengthened by researcher Ursula Voss, who along with her colleagues from the Neurological Laboratory in Frankfurt, Germany, revealed that the brain has heightened activity in the frontal and frontolateral areas during these self-aware dreams.
The science of dreaming is still in its infancy, but neuroscience has come a long way since Dr. Freud in explaining which parts of the brain create dreams.
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