Monday, 29 April 2013
Monday, 22 April 2013
ScienceDaily (Nov. 23, 2011) — They say time heals all wounds, and new research from the University of California, Berkeley, indicates that time spent in dream sleep can help us overcome painful ordeals.UC Berkeley researchers have found that during the dream phase of sleep, also known as REM sleep, our stress chemistry shuts down and the brain processes emotional experiences and takes the edge off difficult memories.
The findings offer a compelling explanation for why people with post-traumatic stress disorder (PTSD), such as war veterans, have a hard time recovering from distressing experiences and suffer reoccurring nightmares. They also offer clues into why we dream.
"The dream stage of sleep, based on its unique neurochemical composition, provides us with a form of overnight therapy, a soothing balm that removes the sharp edges from the prior day's emotional experiences," said Matthew Walker, associate professor of psychology and neuroscience at UC Berkeley and senior author of the study to be published on Nov. 23, in the journal Current Biology.
For people with PTSD, Walker said, this overnight therapy may not be working effectively, so when a "flashback is triggered by, say, a car backfiring, they relive the whole visceral experience once again because the emotion has not been properly stripped away from the memory during sleep."
The results offer some of the first insights into the emotional function of Rapid Eye Movement (REM) sleep, which typically takes up 20 percent of a healthy human's sleeping hours. Previous brain studies indicate that sleep patterns are disrupted in people with mood disorders such as PTSD and depression.
While humans spend one-third of their lives sleeping, there is no scientific consensus on the function of sleep. However, Walker and his research team have unlocked many of these mysteries linking sleep to learning, memory and mood regulation. The latest study shows the importance of the REM dream state.
"During REM sleep, memories are being reactivated, put in perspective and connected and integrated, but in a state where stress neurochemicals are beneficially suppressed," said Els van der Helm, a doctoral student in psychology at UC Berkeley and lead author of the study.
Thirty-five healthy young adults participated in the study. They were divided into two groups, each of whose members viewed 150 emotional images, twice and 12 hours apart, while an MRI scanner measured their brain activity.
Half of the participants viewed the images in the morning and again in the evening, staying awake between the two viewings. The remaining half viewed the images in the evening and again the next morning after a full night of sleep.
Those who slept in between image viewings reported a significant decrease in their emotional reaction to the images. In addition, MRI scans showed a dramatic reduction in reactivity in the amygdala, a part of the brain that processes emotions, allowing the brain's "rational" prefrontal cortex to regain control of the participants' emotional reactions.
In addition, the researchers recorded the electrical brain activity of the participants while they slept, using electroencephalograms. They found that during REM dream sleep, certain electrical activity patterns decreased, showing that reduced levels of stress neurochemicals in the brain soothed emotional reactions to the previous day's experiences.
"We know that during REM sleep there is a sharp decrease in levels of norepinephrine, a brain chemical associated with stress," Walker said. "By reprocessing previous emotional experiences in this neuro-chemically safe environment of low norepinephrine during REM sleep, we wake up the next day, and those experiences have been softened in their emotional strength. We feel better about them, we feel we can cope."
Walker said he was tipped off to the possible beneficial effects of REM sleep on PTSD patients when a physician at a U.S. Department of Veterans Affairs hospital in the Seattle area told him of a blood pressure drug that was inadvertently preventing reoccurring nightmares in PTSD patients.
It turns out that the generic blood pressure drug had a side effect of suppressing norepinephrine in the brain, thereby creating a more stress-free brain during REM, reducing nightmares and promoting a better quality of sleep. This suggested a link between PTSD and REM sleep, Walker said.
"This study can help explain the mysteries of why these medications help some PTSD patients and their symptoms as well as their sleep," Walker said. "It may also unlock new treatment avenues regarding sleep and mental illness."
Other co-authors of the study are UC Berkeley sleep researchers Justin Yao, Shubir Dutt, Vikram Rao and Jared Saletin.
The Guardian, 25 November 2011 referred to the article in Current Biology
No, not the late-lamented band, whom we praised a few weeks ago. We refer to the state in which the twitch of the closed eye betrays the unshackling of the imagination. REM is something shared with many animals. Humans can't even claim to do more than the rest – a glance at the REM league table suggests armadillos dream far bigger dreams. The unlikely connection between the flittering iris and the unconscious mind's eye was first discerned in the 1950s, and was established fact before long. Ever since, we have known we owe our nightly flights of fancy to this distinctive sleep phase which features a complex chemistry and irregular breathing as well as the rapid eye movement itself. We owe to it, too, the whole cultural story of dreaming which stretches from Sumerian myths to Freudian speculation by way of the Bible itself. Throughout, there's been speculation as to why we dream in the first place, and yet most of the myriad "theories" advanced remain just that. Now a paper in Current Biology sheds a little light on what happens in the dark hours. The researchers showed subjects images that pulled on the heartstrings before allowing half – and depriving the rest – of a proper sleep. The next day they saw the images again, and scans revealed that while the raw emotional centres non-sleepers brains still buzzed in response, the sleepers' reasoning apparatus kicked in. Sleep seems to lay demons to rest, or at least allow them to be approached in a dispassionate spirit. Sweet dreams indeed.
Perhaps an example of the process whereby an idea which starts off being ignored, then controversial and rejected finally becomes mainstream and part of the background with no one quite sure where it came from but just obvious when you think about it. Joe's theory links the mystery of dreaming as the leader article says with a rational EXPLANATION so joining two pars of our conscious lives - wondering and digesting satisfying answers.
But as it’s well past midnight I'd better get some rem in myself
If you go to The Guardian web site and search 'In praise of rem' there is a link to the Current Biology
REM Sleep Depotentiates Amygdala Activity to Previous Emotional Experiences
Els van der Helm, Justin Yao, Shubir Dutt, Vikram Rao, Jared M. Saletin, Matthew P. Walker
Sleep and Neuroimaging Laboratory, Department of Psychology, University of California, Berkeley, Berkeley, CA 94720-1650, USA Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720-1650, USA Corresponding author
► Sleep decreases amygdala activity to prior waking emotional experiences ►The amygdala decrease is associated with reestablished prefrontal connectivity ►These neural changes are accompanied by overnight reductions in subjective reactivity ►Reductions in both brain and behavioral reactivity are associated with REM physiology
Clinical evidence suggests a potentially causal interaction between sleep and affective brain function; nearly all mood disorders display co-occurring sleep abnormalities, commonly involving rapid-eye movement (REM) sleep [1,2,3,4]. Building on this clinical evidence, recent neurobiological frameworks have hypothesized a benefit of REM sleep in palliatively decreasing next-day brain reactivity to recent waking emotional experiences [5,6]. Specifically, the marked suppression of central adrenergic neurotransmitters during REM (commonly implicated in arousal and stress), coupled with activation in amygdala-hippocampal networks that encode salient events, is proposed to (re)process and depotentiate previous affective experiences, decreasing their emotional intensity . In contrast, the failure of such adrenergic reduction during REM sleep has been described in anxiety disorders, indexed by persistent high-frequency electroencephalographic (EEG) activity (>30 Hz) [7,8,9,10]; a candidate factor contributing to hyperarousal and exaggerated amygdala reactivity [3,11,12,13]. Despite these neurobiological frameworks, and their predictions, the proposed benefit of REM sleep physiology in depotentiating neural and behavioral responsivity to prior emotional events remains unknown. Here, we demonstrate that REM sleep physiology is associated with an overnight dissipation of amygdala activity in response to previous emotional experiences, altering functional connectivity and reducing next-day subjective emotionality.
Scientific American Mind and Brain 29.12.11
Research finds that dreams may help consolidate and soothe troubled memories and experiences. Christie Nicholson reports
November 28, 2011Sleep also helps us learn. During REM sleep, which is the dreaming stage of sleep, the brain stops releasing stress chemicals. Now a new study finds that as we dream we can even soothe our stressful associations to certain experiences.
Scientists scanned the brains of 35 subjects while they viewed emotionally arousing images. Half of the subjects viewed the images in the morning and again in the evening of the same day. The other half viewed the same images in the evening and then again the next morning after sleeping.
Those who slept between viewings reported a significant decrease in their emotional reaction to seeing the images the second time. And brain scans corroborated the self-reports, showing a reduction of activity in the amygdala, an area responsible for processing emotions.
The research was published in the journal Current Biology.
The researchers note that by processing emotional experiences during REM sleep, when norepinephrine levels are dramatically reduced, we feel less strongly about such experiences when we wake.
As Shakespeare knew when he said that sleep “knits up the ravell’d sleave of care” and was “the balm of hurt minds.”
New research sheds light on how and why we remember dreams--and what purpose they are likely to serve
By Sander van der Linden | July 26, 2011 SciAm M&BFor centuries people have pondered the meaning of dreams. Early civilizations thought of dreams as a medium between our earthly world and that of the gods. In fact, the Greeks and Romans were convinced that dreams had certain prophetic powers. While there has always been a great interest in the interpretation of human dreams, it wasn’t until the end of the nineteenth century that Sigmund Freud and Carl Jung put forth some of the most widely-known modern theories of dreaming. Freud’s theory centred around the notion of repressed longing -- the idea that dreaming allows us to sort through unresolved, repressed wishes. Carl Jung (who studied under Freud) also believed that dreams had psychological importance, but proposed different theories about their meaning.
Since then, technological advancements have allowed for the development of other theories. One prominent neurobiological theory of dreaming is the “activation-synthesis hypothesis,” which states that dreams don’t actually mean anything: they are merely electrical brain impulses that pull random thoughts and imagery from our memories. Humans, the theory goes, construct dream stories after they wake up, in a natural attempt to make sense of it all. Yet, given the vast documentation of realistic aspects to human dreaming as well as indirect experimental evidence that other mammals such as cats also dream, evolutionary psychologists have theorized that dreaming really does serve a purpose. In particular, the “threat simulation theory” suggests that dreaming should be seen as an ancient biological defence mechanism that provided an evolutionary advantage because of its capacity to repeatedly simulate potential threatening events – enhancing the neuro-cognitive mechanisms required for efficient threat perception and avoidance.
So, over the years, numerous theories have been put forth in an attempt to illuminate the mystery behind human dreams, but, until recently, strong tangible evidence has remained largely elusive.
Yet, new research published in the Journal of Neuroscience provides compelling insights into the mechanisms that underlie dreaming and the strong relationship our dreams have with our memories. Cristina Marzano and her colleagues at the University of Rome have succeeded, for the first time, in explaining how humans remember their dreams. The scientists predicted the likelihood of successful dream recall based on a signature pattern of brain waves. In order to do this, the Italian research team invited 65 students to spend two consecutive nights in their research laboratory.
During the first night, the students were left to sleep, allowing them to get used to the sound-proofed and temperature-controlled rooms. During the second night the researchers measured the student’s brain waves while they slept. Our brain experiences four types of electrical brain waves: “delta,” “theta,” “alpha,” and “beta.” Each represents a different speed of oscillating electrical voltages and together they form the electroencephalography (EEG). The Italian research team used this technology to measure the participant’s brain waves during various sleep-stages. (There are five stages of sleep; most dreaming and our most intense dreams occur during the REM stage.) The students were woken at various times and asked to fill out a diary detailing whether or not they dreamt, how often they dreamt and whether they could remember the content of their dreams.
While previous studies have already indicated that people are more likely to remember their dreams when woken directly after REM sleep, the current study explains why. Those participants who exhibited more low frequency theta waves in the frontal lobes were also more likely to remember their dreams.
This finding is interesting because the increased frontal theta activity the researchers observed looks just like the successful encoding and retrieval of autobiographical memories seen while we are awake. That is, it is the same electrical oscillations in the frontal cortex that make the recollection of episodic memories (e.g., things that happened to you) possible. Thus, these findings suggest that the neurophysiological mechanisms that we employ while dreaming (and recalling dreams) are the same as when we construct and retrieve memories while we are awake.
In another recent study conducted by the same research team, the authors used the latest MRI techniques to investigate the relation between dreaming and the role of deep-brain structures. In their study, the researchers found that vivid, bizarre and emotionally intense dreams (the dreams that people usually remember) are linked to parts of the amygdala and hippocampus. While the amygdala plays a primary role in the processing and memory of emotional reactions, the hippocampus has been implicated in important memory functions, such as the consolidation of information from short-term to long-term memory.
The proposed link between our dreams and emotions is also highlighted in another recent study published by Matthew Walker and colleagues at the Sleep and Neuroimaging Lab at UC Berkeley, who found that a reduction in REM sleep (or less “dreaming”) influences our ability to understand complex emotions in daily life – an essential feature of human social functioning. Scientists have also recently identified where dreaming is likely to occur in the brain. A very rare clinical condition known as “Charcot-Wilbrand Syndrome” has been known to cause (among other neurological symptoms) loss of the ability to dream. However, it was not until a few years ago that a patient reported to have lost her ability to dream while having virtually no other permanent neurological symptoms. The patient suffered a lesion in a part of the brain known as the right inferior lingual gyrus (located in the visual cortex). Thus, we know that dreams are generated in, or transmitted through this particular area of the brain, which is associated with visual processing, emotion and visual memories.
Taken together, these recent findings tell an important story about the underlying mechanism and possible purpose of dreaming.
Dreams seem to help us process emotions by encoding and constructing memories of them. What we see and experience in our dreams might not necessarily be real, but the emotions attached to these experiences certainly are. Our dream stories essentially try to strip the emotion out of a certain experience by creating a memory of it. This way, the emotion itself is no longer active. This mechanism fulfils an important role because when we don’t process our emotions, especially negative ones, this increases personal worry and anxiety. In fact, severe REM sleep-deprivation is increasingly correlated to the development of mental disorders. In short, dreams help regulate traffic on that fragile bridge which connects our experiences with our emotions and memories.
ABOUT THE AUTHOR(S)Sander van der Linden is a doctoral researcher in social experimental psychology at the London School of Economics and Political Science. His research is concerned with the process of behavioral change and funded by the Grantham Research Institute on Climate Change and the Environment.
A Role for REM Sleep in Recalibrating the Sensitivity of the Human Brain to Specific Emotions Ninad Gujar et al
Although the impact of sleep on cognitive function is increasingly well established, the role of sleep in modulating affective brain processes remains largely uncharacterized. Using a face recognition task, here we demonstrate an amplified reactivity to anger and fear emotions across the day, without sleep. However, an intervening nap blocked and even reversed this negative emotional reactivity to anger and fear while conversely enhancing ratings of positive (happy) expressions.
Most interestingly, only those subjects who obtained rapid eye movement (REM) sleep displayed this remodulation of affective reactivity for the latter 2 emotion categories. Together, these results suggest that the evaluation of specific human emotions is not static across a daytime waking interval, showing a progressive reactivity toward threat-related negative expressions. However, an episode of sleep can reverse this predisposition, with REM sleep depotentiating negative reactivity toward fearful expressions while concomitantly facilitating recognition and ratings of reward-relevant positive expressions. These findings support the view that sleep, and specifically REM neurophysiology, may represent an important factor governing the optimal homeostasis of emotional brain regulation.
Full paper: http://walkerlab.berkeley.edu/reprints/Gujar-Walker_CC_2011.pdf