Physiological theories claim that dreams are a product of some kind of existing disorder in the brain. Physiological theories claim that dreams are a product of neural firing in the brain, which can sometimes, according to some theorists, aid in the process of learning. This is why it is recommended to get good sleep before a test! Psychological theories claim dreams are a way of processing issues in our lives, founded in Freud's initial dream theory, which posited dreams as ways we process repressed feelings and desires.
There are many who believe dreams are a combination of both theories; they are random, but still serve some purpose. Stage 4 sleep is referred to as delta sleep, or deep sleep. It is very hard to wake someone in this stage of sleep.
Unlike REM sleep, there are no eye or muscle movements. A patient is slightly overweight and has trouble sleeping. He keeps waking up gasping for air, disrupting his sleeping patterns. What is the most likely diagnosis for this patient? Sleep apnea is characterized by pauses or lack of breathing when sleeping. A lack of oxygen to the brain causes a buildup of carbon dioxide in the bloodstream. Accumulated carbon dioxide causes the person to wake up, gasping for air. Normal breathing upon wakefulness will allow normal oxygen flow until the person falls back asleep.
Sleep apnea is more common among middle aged and overweight individuals. While genetics play a significant role, those with enlarged tonsils, allergies which may cause swelling of the throat , sinus problems, or enlarged necks are also at risk of sleep apnea.
Memory is encoded during REM sleep. In the hippocampus, neurons fire four times as opposed to once as a result of ponto-geniculo-occipital PGO spikes. Memories from a day's activities and learning are encoded in the hippocampus four times, contributing to long-term memory. Theta waves are also associated with this stage of sleep and contribute to REM's restorative nature. REM sleep or Rapid Eye Movement is the stage in which dreams occur, because even though the body is essentially paralyzed, this stage is accompanied by intense activity in the brain.
The term "healthy lifestyle" may be broadly defined from culture to culture. While sleep is healthy and good for the body, too much sleep may also be detrimental, or a sign of severe depression. This answer choice is too broad, and not specific enough in its limitations on sleep, to be accurate. If you've found an issue with this question, please let us know.
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Hanley Rd, Suite St. Louis, MO Sleep spindles are generated in the reticular nucleus of the thalamus, and may represent periods in which the brain is inhibiting processing to keep the sleeper in a tranquil state. During sleep these spindles are seen in the brain as a burst of activity immediately following muscle twitching. Spindles have been shown to aid sleeping in the presence of disruptive external sounds, and have also been associated with the integration of new information into existing knowledge, as well as with directed remembering and forgetting.
K-c o mplexes are high-voltage events that occur more frequently in the first sleep cycles. K-complexes are thought to have two main purposes:. Sleep spindles and K-complexes : Sleep spindles and K-complexes are defining characteristics and indicate the onset of stage 2 NREM sleep. During this stage, muscular activity decreases, and conscious awareness of the external environment disappears.
It is also characterized by:. This is the stage in which different forms of parasomnia, such as night terrors, nocturnal enuresis, sleepwalking, and somniloquy sleep talking typically occur. This stage, formerly divided into two separate stages 3 and 4 , is called slow-wave sleep, or SWS. In SWS, the sleeper is less responsive to the environment; many environmental stimuli no longer produce any reactions. The sleeper now enters rapid eye movement REM sleep. In this stage, most muscles are paralyzed.
This level is also referred to as paradoxical sleep because the sleeper, although exhibiting EEG waves similar to a waking state, is harder to arouse than at any other sleep stage. Most memorable dreaming occurs in this stage. Partial paralysis occurs, perhaps to protect organisms from self-damage through physically acting out scenes from the often-vivid dreams that occur during this stage.
Vital signs indicate arousal, and oxygen consumption by the brain is higher than when the sleeper is awake. Sleep has four distinct phases, or stages. Sleep progresses from stage 1 to stage 2 to stage 3, and then back to stage 2 before transitioning into the REM phase.
Once the REM phase is over, stage 2 will repeat. A person will complete this entire cycle about four or five times given a full night of sleep. Note that stages 3 and 4 are now considered to be one stage, stage 3. A sleeper first enters REM sleep after about an hour and a half of sleep, and then the phase will last only briefly.
However, for each successive sleep cycle, the proportion of the cycle spent in REM sleep increases, up to an hour long in later cycles. This is why it is important for humans to sleep in long stretches e. Sleep deprivation tends to cause slower brain waves in the frontal cortex, shortened attention span, higher anxiety, impaired memory, and an unhappy mood. Conversely, a well-rested organism tends to have improved memory and mood. Research has demonstrated that some sleep stages are more important than others in achieving restfulness.
For example, REM deprivation causes a significant increase in the number of attempts to go into the REM stage while asleep. These findings are consistent with the idea that REM sleep is biologically necessary. REM sleep is thought to be largely responsible for the time that our brains take to consolidate learning and memory.
Similarly, sleeping in short bursts is not sufficient for restfulness because it does not allow our bodies enough time for a complete cycle of sleep. Sleep disorders cause sleep disturbances that affect the amount, quality, or timing of sleep or that induce abnormal events during sleep.
Sleep-wake disorders cause a number of sleep disturbances that affect the amount, quality, or timing of sleep or that induce abnormal events during sleep. Some sleep-wake disorders are serious enough to interfere with normal physical, mental, and emotional functioning. Disruptions in sleep can be caused by a variety of issues, from teeth grinding bruxism to night terrors.
Polysomnography is a technique that can be used to identify some sleep disorders. It is often a symptom of a mood disorder e. However, it can also be a disorder in its own right. Hypersomnolence disorder also known as idiopathic hypersomnia is a disease of likely neurological origin that is characterized primarily by severe, excessive daytime sleepiness. It has been diagnosed only rarely and is often very difficult to diagnose at an early stage.
It is usually a debilitating lifelong disease. There is a very low level of public awareness of this disorder, which often results in stigmatization of those who suffer from it. Currently, there is no cure, there are no FDA-approved treatments, and research funding for the study of this disorder is scarce. Narcolepsy is also referred to as excessive daytime sleepiness EDS.
Individuals with this disorder often fall asleep spontaneously but unwillingly at inappropriate times. People with narcolepsy tend to have trouble in areas such as work, leisure, and personal relationships. Narcolepsy : Narcolepsy is characterized by an individual uncontrollably falling asleep very suddenly, typically in inappropriate situations. Some sleep disorders are caused by disturbances in breathing. Sleep apnea, for example, is a disorder in which obstruction of the airway during sleep causes a lack of sufficient deep sleep, often accompanied by snoring.
Sleep apnea is usually caused by some sort of physical condition that obstructs the breathing system, such as obesity, rather than a mental condition. The DSM-5 names two types of sleep apnea: obstructive sleep apnea, in which your airway collapses during sleep, and central sleep apnea, in which your brain does not signal your lungs to continue to inhale. Individuals with sleep apnea often feel tired throughout the day, as the constant breaks in their sleep cycle cause unrestful nights.
Parasomnias are a category of sleep disorders that involve abnormal movements, behaviors, emotions, perceptions, and dreams that occur while falling asleep, while sleeping, while between sleep stages, or during arousal from sleep.
Most parasomnias are due to partial arousal during the transitions between wakefulness and non-rapid-eye-movement N-REM sleep or between wakefulness and rapid-eye-movement REM sleep.
The hypothesis states that the function of sleep is to process, encode, and transfer data from short-term memory to long-term memory through a process called consolidation.
However, there is not much evidence to back this up. NREM sleep processes the conscious-related memory declarative memory , and REM sleep processes the unconscious related memory procedural memory. The underlying assumption of continual-activation theory is that, during REM sleep, the unconscious part of the brain is busy processing procedural memory. Meanwhile, the level of activation in the conscious part of the brain descends to a very low level as the inputs from the senses are basically disconnected.
Review the purpose and stages of sleep as well as the reasons why we dream in the following CrashCourse video:. Privacy Policy. Skip to main content. Module 4: States of Consciousness. Search for:. Dreams and Dreaming Learning Objectives Describe and differentiate between theories on why we dream. The eye movements of REM sleep would allow the dreamer to scan the imaginary scene of the dream the scanning hypothesis ; the cerebral cortex activation revealed by the rapid EEG would allow intense cognitive activity, creating the complex stories of a dream; and the lack of muscle tone would prevent the dreamer from acting out his dreams.
From that time on, researchers investigated REM sleep to obtain answers about dreaming. In the s, researchers used functional neuroimaging techniques such as positron emission tomography PET to investigate brain activity during REM sleep in humans. This new approach enabled researchers to demonstrate that the functional organization of the brain during REM sleep is different from the functional organization of the brain during wakefulness Maquet et al.
In comparison to wakefulness, brain activity during REM sleep is decreased in some brain regions e. Looking more generally for brain activity correlating with REM sleep the vigilance states considered included wakefulness, slow-wave sleep, and REM sleep , Maquet et al. Based on these results, researchers argued that the particular functional organization of the brain during REM sleep could explain the phenomenological characteristics of dream reports Hobson and Pace-Schott, ; Schwartz and Maquet, ; Maquet et al.
They considered that brain activity increases and decreases during REM sleep could be interpreted on the basis of what we know about brain activity during wakefulness. In this context, the increased occipital cortex activity during REM sleep could explain the visual component of dream reports because neuroimaging results during wakefulness showed that visual imagery with the eyes closed activates the occipital cortex Kosslyn and Thompson, The decreased activity in the temporoparietal junction during REM sleep may explain why dreams are mainly experienced in the egocentric coordinates of the first-person; indeed, during wakefulness, activity in the temporoparietal junction was reported to be greater for allocentric vs.
The increased activity in the hippocampus during REM sleep could explain why dreams are often composed of known images or characters, as the hippocampus is known to be associated with the encoding and retrieval of lived events during wakefulness e. Indeed, during wakefulness, the lateral prefrontal cortex is involved in executive function, cognitive control, and working memory Petrides, ; Koechlin and Hyafil, The increased activity in the medial prefrontal cortex during REM sleep could explain the attribution of thoughts, beliefs, and emotions to the characters in the dream because, during wakefulness, the medial prefrontal cortex is known to participate in mind reading Ruby et al.
In conclusion, results from experimental psychology and neuroscience allow us to better understand the phenomenology of dreaming and the cerebral correlates of some characteristics of dream reports.
Still, what do they tell us about the role of dreaming? What are the current hypotheses about dream function s? At the end of the twentieth century, the neurologist Alan Hobson, who was profoundly anti-psychoanalysis, proposed a theory that deprived dreaming of any function. This lesion resulted in the appearance of movements during REM sleep. Movies from the Jouvet lab show sleeping cats performing complex motor actions with altered control and coordination resembling those of wakefulness, such as fur licking, growling, chasing prey, mastication, and fighting.
Later in his career, Jouvet moved toward a hypothesis focusing on the role of dreaming in the individual dimension. We thus have to explain how certain aspects of psychological heredity found in homozygote twins raised in different surroundings may persist for a whole life psychological individuation.
A definitive genetic programming during development by neurogenesis is unlikely due to the plasticity of the nervous system. That is why we have to consider the possibility of an iterative genetic programming. The internal mechanisms synchronous of paradoxical sleep SP are particularly adapted to such programming. This would activate an endogenous system of stimulation that would stimulate and stabilize receptors genetically programmed by DNA in some neuronal circuits.
The excitation of these neurons during SP leads to oniric behaviors that could be experimentally revealed — the lists of these behaviors are specific to each individual and indirect data suggest a genetic component of this programming. Amongst the mechanisms allowing the iterative programming of SP, sleep is particularly important.
Security — and hence the inhibition of the arousal system — is a sine qua non-condition for genetic programming to take place. This process would ensure the stability of personality across time. The Finnish psychologist Antti Revonsuo recently proposed a hypothesis called threat simulation theory, which explains the fearful characteristics of dream content Revonsuo, ; Valli and Revonsuo, According to this theory, dreams serve as virtual training places to improve threat avoidance or threat fighting ability.
The theory postulates that such nocturnal training makes the dreamer more efficient at resolving threatening situations during wakefulness. Cartwright et al. Her team showed that, in healthy subjects, the depression level before sleep was significantly correlated with affect in the first REM report.
Her team also observed that low scorers on the depression scale displayed a flat distribution of positive and negative affect in dreams, whereas those with a depressed mood before sleep showed a pattern of decreasing negative and increasing positive affect in dreams reported from successive REM periods Cartwright et al. The researchers concluded that negative dreams early in the night may reflect a within-sleep mood regulation process, whereas those that occur later may indicate a failure in the completion of this process.
Finally, a current mainstream hypothesis in cognitive neuroscience credits sleep and dreaming with a role in memory consolidation for a recent review, see Diekelmann and Born, Numerous studies have shown that brain activity during training is replayed during post-training sleep e. Decreased performance during the post-training day in sleep-deprived subjects further suggested that the replay of brain activity at night contributes to memory consolidation e.
Only recently, however, have experimental results in humans argued in favor of a role of dreaming per se in memory consolidation. In one study, subjects were trained on a virtual navigation task before taking a nap. Post-nap tests showed that subjects who dreamed about the task performed better than subjects who did not dream note that only 4 out of 50 subjects dreamed about the task in this study; Wamsley et al.
Using a different approach, Nielsen and colleagues provided additional arguments supporting a link between dreams and memory Nielsen et al. The similarity between the delay of episodic event incorporation into dreams and the delay of post-training cellular plasticity in the hippocampus led the Canadian team to suggest a link between dreaming and episodic memory consolidation. In summary, the preceding section describes the current state of the art on dreaming, its phenomenology and cerebral correlates and hypotheses about its functions.
Some substantial advances have been made, but much remains to be understood. A piece of evidence in favor of a strong link between REM sleep and dreaming is the oneiric behavior the appearance of complex motor behaviors when motor inhibition is suppressed during REM sleep discovered by Sastre and Jouvet in cats and reproduced by Sanford et al.
Researchers interpreted these results as the animal acting out its dream. However, as animals do not talk, the link between oneiric behavior and dream recall cannot be tested experimentally. This limitation seriously hampers our understanding of dreaming. In humans, complex motor behaviors e. It can be caused by substance withdrawal e.
According to physicians experts on this syndrome, some patients report dreams that are consistent with their behaviors in REM sleep Mahowald and Schenck, According to the literature, however, such matches seem to be loose and not systematic.
Only one study has tested whether observers can link dream content to sleep behaviors in RBD Valli et al. In this study, each video recording of motor manifestations was combined with four dream reports, and seven judges had to match the video clip with the correctly reported dream content.
The authors found that reported dream content can be linked to motor behaviors at a level better than chance. However, only Note, however, that because the authors obtained only movements and not behavioral episodes for many RBD patients, the link between videos and dream reports was unfairly difficult to make. It is important to note that motor behavior during sleep can happen outside of REM sleep. Sleepwalking and sleep terrors, which occur during NREM sleep, are usually not considered dream enactments.
In addition, Oudiette et al. Consequently, the authors concluded that sleepwalking may represent an acting out of corresponding dreamlike mentation. Recent research suggests that any kind of motor behavior during sleep can be considered an oneiric behavior. One of the challenges for future research is to test the strength of the link between these oneiric behaviors and dream reports in a controlled and systematic way.
Despite the numerous neuroimaging studies of sleep in humans, the neurophysiological correlates of dreaming remain unclear. This phenomenon is difficult to understand given what we currently know about the sleeping brain and about dreaming.
One explanation may rely on the possibility that brain activity during sleep is not as stable as we think. Brain activity during REM sleep in humans is considered to be well understood Hobson and Pace-Schott, ; Schwartz and Maquet, ; Nir and Tononi, , but several results question this notion.
First, contrary to the common belief that dorsolateral prefrontal cortex activity decreases during REM sleep, several studies have reported increased activity in the dorsolateral prefrontal cortex during REM sleep Hong et al. Second, brain activity during REM sleep is heterogeneous. Finally, few congruencies have been noted in the results of studies investigating brain activity during REM sleep Hong et al.
Furthermore, few brain regions are consistently reported across the majority of the studies. This inconsistency suggests great intra- and intersubject variability in brain activity during REM sleep in humans. A challenge for future research will be to find out whether the variability in brain activity during REM sleep can be explained by the variability in dream content.
Because dream reports can be collected after awakenings from any sleep stage, one may hypothesize that the brain activity that subserves dreaming if such brain activity is reproducible across dreams is quite constant throughout the night and can be observed during all sleep stages. Some results have supported this hypothesis and encouraged further attention in this direction.
Buchsbaum et al. Interestingly, some authors have suggested that decreased power in the alpha band during wakefulness reflects search and retrieval processes in long-term memory for a review, see Klimesch, This result tells us that internal processes control and shape dream content and thus help us to constrain and shape hypotheses about the function and biological basis of dreaming.
At the end of the nineteenth century, Saint-Denys showed that a sensory stimulus e. The author demonstrated that the external world can influence dream content in a direct or indirect way. Finally, it appears that both external and internal parameters can shape or govern dream content. Nonetheless, few of these parameters are known, and some regularities in the phenomenology of dreams suggest that more influencing parameters remain to be discovered. For example, some individuals experience recurring themes, characters, or places in their dreams.
However, the rule s governing which lived events are incorporated into dreams remain unknown. Do the representations constituting the dream emerge randomly from the brain, or do they surface according to certain parameters? Psychoanalysis, which was developed by the neurologist Sigmund Freud in the beginning of the twentieth century, proposes answers to the questions raised above. Indeed, his theory of the human mind comprises hypotheses about the rules of selection and organization of the representations that constitute dreams.
At the beginning of the twentieth century, Freud presented the concept of the unconscious. He proposed that a part of our mind is made up of thoughts, desires, emotions, and knowledge that we are not aware of, but that nevertheless profoundly influence and guide our behaviors.
In his books e. Its expression, however, is coded within dreams the work of dream , and unconscious thoughts are distorted before they emerge in the conscious mind of the sleeping subject manifest content of the dream. As a consequence, the dreamer is not disturbed by repressed and unacceptable thoughts latent content of the dream and can continue sleeping this is the reason why Freud considered dreams the guardians of sleep.
As a consequence, Freud developed techniques to decode dreams and provide a way for an analyst to look inside the words and unconscious images of the patient, and to free them through patient insight.
One of these techniques is called free association, and is regarded as an essential part of the psychoanalytic therapy process. Free association is the principle that the patient is to say anything and everything that comes to mind.
Over time, the therapist or analyst will draw associations between the many trains of uncensored speech the patient shares during each session.
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