Sleep and dreaming: The how, where and why

Within a few hours of reading this you will lose consciousness and slip into a strange twilight world. Where does your mind go during that altered state – or more accurately states – we call sleep? And what is so vital about it that we must spend a third of our lives sleeping? In these articles, we review the latest ideas on why we sleep and look at new ways to enhance its benefits.

Previously unknown sleep pattern revealed in University of Sydney research

There’s no need to panic if you didn’t get a solid eight hours of beauty sleep last night. According to new University of Sydney research, sleep duration naturally waxes and wanes over a period of days regardless of individual lifestyle, timing of sleep or waking, and social and environmental influences.

With further research, the discovery could have important implications for predicting work performance, managing fatigue-related accidents after shift work, and treatment recovery in clinical populations.

"Sleep requirements vary in a cyclical fashion and between individuals. If you incur a sleep debt, your body will signal a need to catch up on extra sleep," says Dr Chin Moi Chow, principal investigator of the article published in Nature and Science of Sleep.

"As you increase your sleep duration to recover from the debt, your ability to prolong wakefulness increases. Then, as prior wakefulness increases, sleepiness is inevitable, and a need for further sleep develops again."

Dr Chow and colleagues Shi Wong and Dr Mark Halaki, from the University’s Faculty of Health Sciences, monitored a group of healthy young males over a fortnight using an actigraph - a small activity recording device worn like a wristwatch on the non-dominant arm - designed to measure sleep patterns.

To the researchers’ fascination, the actigraph data showed participants’ sleep duration oscillated in a sine wave pattern - a phenomenon that had not previously been observed. Clear periodic patterns were found in the majority of the participants, varying from periods of between two and 18 days.

The cyclic pattern observed in the research suggests that the sleep balance mechanism operates on an ongoing basis in daily life, with changes in sleep duration constantly accompanied by compensatory adjustments.

Interestingly, despite the fact that participants in the study habitually slept below the recommended seven to eight hours a night, they still maintained a cyclic sleep duration pattern.

"Our sleep quantity and quality vary according to a range of factors," Dr Chow says. "Some individuals have a slower accumulation or faster dissipation of sleep pressure, which may define their pattern of total sleep time."

Variations in daily sleep duration may also arise from differences such as slight variations in the body clock or external factors like temperature, daylight, exercise, or eating and drinking patterns.

"Changing your sleep patterns on weekends, or resetting the pattern through shift work, could alter your sleep duration cycle and could put the body under significant strain," says Dr Chow.

This research is part of Dr Chow’s broader interest in the lifestyle factors influencing sleep. The team hopes to follow the research by examining the cyclical phenomenon in special groups such as long or short sleepers and people with insomnia.

Poor sleep in old age prevents the brain from storing memories

The connection between poor sleep, memory loss and brain deterioration as we grow older has been elusive. But for the first time, scientists at the University of California, Berkeley, have found a link between these hallmark maladies of old age. Their discovery opens the door to boosting the quality of sleep in elderly people to improve memory.

UC Berkeley neuroscientists have found that the slow brain waves generated during the deep, restorative sleep we typically experience in youth play a key role in transporting memories from the hippocampus – which provides short-term storage for memories – to the prefrontal cortex’s longer term “hard drive.”

However, in older adults, memories may be getting stuck in the hippocampus due to the poor quality of deep ‘slow wave’ sleep, and are then overwritten by new memories, the findings suggest.

“What we have discovered is a dysfunctional pathway that helps explain the relationship between brain deterioration, sleep disruption and memory loss as we get older – and with that, a potentially new treatment avenue,” said UC Berkeley sleep researcher Matthew Walker, an associate professor of psychology and neuroscience at UC Berkeley and senior author of the study published in the journal Nature Neuroscience.

Reviewing alcohol’s effects on normal sleep

Sleep is supported by natural cycles of activity in the brain and consists of two basic states: rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. Typically, people begin the sleep cycle with NREM sleep followed by a very short period of REM sleep, then continue with more NREM sleep and more REM sleep, this 90 minute cycle continuing through the night. A review of all known scientific studies on the impact of drinking on nocturnal sleep has clarified that alcohol shortens the time it takes to fall asleep, increases deep sleep, and reduces REM sleep.

Results will be published in the April 2013 issue of Alcoholism: Clinical & Experimental Research and are currently available at Early View.

"This review has for the first time consolidated all the available literature on the immediate effects of alcohol on the sleep of healthy individuals," said Irshaad Ebrahim, medical director at The London Sleep Centre as well as corresponding author for the study.

"Certainly a mythology seems to have developed around the impact of alcohol on sleep," added Chris Idzikowski, director of the Edinburgh Sleep Centre. "It is a good time to review the research as the mythology seems to be flourishing more rapidly than the research itself. Also, our understanding of sleep has accelerated in the past 30 years, which has meant that some of the initial interpretations need to be revisited."

Some of the review’s key themes are:

• At all dosages, alcohol causes a reduction in sleep onset latency, a more consolidated first half sleep, and an increase in sleep disruption in the second half of sleep.

  "This review confirms that the immediate and short-term impact of alcohol is to reduce the time it takes to fall asleep," said Ebrahim. "In addition, the higher the dose, the greater the impact on increasing deep sleep. This effect on the first half of sleep may be partly the reason some people with insomnia use alcohol as a sleep aid. However, the effect of consolidating sleep in the first half of the night is offset by having more disrupted sleep in the second half of the night."

• The majority of studies, across alcohol dose, age, and gender, confirm an increase in slow-wave sleep (SWS) in the first half of the night. SWS, often referred to as deep sleep, consists of stages 3 and 4 of NREM. During SWS, the body repairs and regenerates tissues, builds bone and muscle, and appears to strengthen the immune system. Alcohol’s impact on SWS in the first half of the night appears to be more robust than its effect on REM sleep.

  "SWS or deep sleep generally promotes rest and restoration," said Ebrahim. "However, when alcohol increases SWS, this may also increase vulnerability to certain sleep problems such as sleepwalking or sleep apnoea in those who are predisposed."

• Alcohol’s effects on REM sleep in the first half of sleep appear to be dose related. Low and moderate doses show no clear effects on REM sleep in the first half of the night, whereas at high doses, REM sleep reduction in the first part of sleep is significant. Total night REM sleep percent is decreased in the majority of studies at moderate and high doses.

  "Dreams generally occur in the REM stage of sleep," said Ebrahim. "During REM sleep the brain is more active, and may be regarded as ‘defragmenting the drive.’ REM sleep is also important because it can influence memory and serve restorative functions. Conversely, lack of REM sleep can have a detrimental effect on concentration, motor skills, and memory. REM sleep typically accounts for 20 to 25 percent of the sleep period."

• The onset of the first REM sleep period is significantly delayed at all doses and appears to be the most recognizable effect of alcohol on REM sleep, followed by a reduction in total night REM sleep.

"One consequence of a delayed onset of the first REM sleep would be less restful sleep," said Idzikowski. "The first REM episode is often delayed in stressful environments. There is also a linkage with depression."

520-Day Simulated Mission to Mars Reveals Critical Data about Sleep and Activity Needs for Astronauts

In the first study of its kind, a team of researchers led by faculty at the Perelman School of Medicine at the University of Pennsylvania and the Baylor College of Medicine, has analyzed data on the impact of prolonged operational confinement on sleep, performance, and mood in astronauts from a groundbreaking international effort to simulate a 520-day space mission to Mars. The findings, published online-first in the Proceedings of the National Academy of Sciences, revealed alterations of life-sustaining sleep patterns and neurobehavioral consequences for crew members that must be addressed for successful adaption to prolonged space missions.

"The success of human interplanetary spaceflight, which is anticipated to be in this century, will depend on the ability of astronauts to remain confined and isolated from Earth much longer than previous missions or simulations," said David F. Dinges, PhD, professor and chief, Division of Sleep and Chronobiology in the Department of Psychiatry at the Perelman School of Medicine, and co-lead author of the new study. "This is the first investigation to pinpoint the crucial role that sleep-wake cycles will play in extended space missions."

The 520-day simulation, which was developed by the Institute for Biomedical Problems (IBMP) of the Russian Academy of Sciences, and sponsored in part by the European Space Agency (ESA), was initiated on June 3, 2010 when the hatches were closed on a 550-cubic-meter IBMP spacecraft-like confinement facility in Russia. The simulated mission, involving an international, six-man team of volunteers, involved more than 90 experiments and realistic scenarios to gather valuable psychological and medical data on the effects of a long-term deep space flight. The 520-day mission was broken into three phases: 250 days for the trip to Mars, 30 days on the surface, and 240 days for the return to Earth.

“As the only U.S. research team involved with the Mars 520-day simulation, the study required international coordination and strong collaborations to ensure that the experiments were conducted in a thorough and rigorous manner,” said Jeffrey P. Sutton, MD, PhD, professor and director, Center for Space Medicine at Baylor College of Medicine, and senior study author. The investigators monitored the crew’s rest-activity patterns, performance and psychological responses to determine the extent to which sleep loss, fatigue, stress, mood changes and conflicts occurred during the mission.

Measurements included continuous recordings of body movements using wrist actigraphy (a noninvasive means of estimating sleep and movement intensity), and light exposure and weekly computer-based neurobehavioral assessments to identify changes in the crew’s activity levels, sleep quantity and quality, sleep–wake intervals, alertness performance, and workload throughout the 17 months of mission confinement.

Data from the actigraph devices revealed that crew sedentariness increased across the mission, as illustrated by decreased waking movement and increased sleep and rest times. The majority of crewmembers also experienced one or more disturbances of sleep quality, alertness deficits, or altered sleep–wake intervals and timing, suggesting inadequate circadian synchronization.

"Taken together, these measurements point to the need to identify markers of differential vulnerability to abnormal decrease in muscular movement and sleep– wake changes in crew members during the prolonged isolation of exploration spaceflight and the need to ensure maintenance of the Earth’s natural circadian rhythm, sleep quantity and quality, and optimal activity levels during exploration missions," said Mathias Basner, MD, PhD, MSc, assistant professor of Sleep and Chronobiology in Psychiatry at Penn, and co-lead author.

The research team concludes that successful adaptation to such missions will require crews to transit in spacecraft and live in surface habitats that artificially mimic aspects of Earth’s sleep-wake activity cycles, such as appropriately timed light exposure, food intake, and exercise. This dynamic will be necessary to maintain neurocognition and human behavior throughout the flight.

Decoding Dreams

“[I was] somewhere, in a place like a studio to make a TV program or something,” a groggy study participant recounted (in Japanese). “A male person ran with short steps from the left side to the right side. Then, he tumbled.” The participant had recently been awoken by Masako Tamaki, a postdoc in the lab of neuroscientist Yukiyasu Kamitani of the ATR Computational Neuroscience Laboratories in Kyoto, Japan. He was lying in a functional magnetic resonance imaging (fMRI) scanner, doing his best to recall what he had been dreaming about. “He stumbled over something, and stood up while laughing, and said something,” the participant continued. “He said something to persons on the left side.”

At first blush, the story doesn’t seem particularly informative. But the study subject saw a man, not a woman. And he was inside some sort of workplace. That fragmented information is enough for Kamitani and his team, who recorded dream appearances of 20 key objects, such as “male” or “room,” and used a machine-learning algorithm to correlate those concepts with the fMRI images to find patterns that could be used to predict what people were dreaming about without having to wake them. Such information could help inform the study of why people dream, an elusive question in neurobiology, Kamitani says. “Knowing what is represented during sleep would help to understand the function of dreaming.”

Analyzing more than 200 dream reports—some 30–45 hours of interviews with each of three participants—Kamitani and his colleagues built a “dream-trained decoder” based on fMRI imagery of the V1, V2, and V3 areas of the visual cortex. “We find some rule, or mapping, or pattern between what the person is seeing and what activity is happening in the brain,” Kamitani explains. And it worked, according to Kamitani, who presented the results at the Society for Neuroscience meeting in New Orleans in October 2012, predicting whether or not the 20 objects occurred in dreams with 75–80 percent accuracy.

But while Kamitani’s dream-decoding study is interesting, says neurobiologist David Kahn of Harvard Medical School, the algorithms used are quite primitive, only providing a handful of clues about the dream’s content. “We still have a long way to go before we can actually re-create the story that is the dream,” he says. “This is almost science fiction, because we’re way, way far from it … [but] this is an added tool.”

“Decoding is very primitive,” Kamitani agrees, “but I think there are a lot of potentials.” One way to get a more complete picture of the dream is to increase the complexity of the decoder, he notes. In this first study, for example, the researchers focused on nouns representing visual objects, but going forward, Kamitani says he hopes to include other concepts, like verbs. “By analyzing that aspect we may be able to add some action aspects in the dream.”

Furthermore, researchers might not have to fully interpret the dream themselves to benefit from the new decoder. Instead, the clues gleaned from the fMRI images could simply be used to jog participants’ memories. “We know that dreams—even the most vivid dreams we remember, [like] nightmares or lucid dreams—are really fragile memories,” says Antonio Zadra, an experimental psychologist at the University of Montreal. “Unless you wrote it down or told it to someone in the morning, usually even before lunch, that memory will start fading. And by night, you might just have the essence.”

Unfortunately, that failing memory was the only resource for researchers studying dreams. Now, with a little bit of supplemental information, they may be able to help participants recall dreams more precisely. “The subjective reports are never complete,” Kamitani says. “By giving the subject what we reconstructed, they may remember something more.”

At an even more basic level, the decoder could help scientists understand what’s happening in the brain during dreaming. “To create this whole virtual world out of nothing—with no visual input or auditory input—is quite fascinating and undoubtedly very complex,” Zadra says. “This research will certainly help us better understand what brain areas are doing what, to even allow for this to happen.”

In Kamitani’s study, for example, the researchers found that areas of higher-level visual processing, which respond to more abstract features, were more useful for interpreting dream content than lower-level processing areas. This makes sense, given that those lower areas of the visual cortex are more closely connected to the direct input from the retina. But, Kamitani notes, this could simply have to do with the way the study was designed. “We didn’t train the decoder with low-level visual features,” such as shape or contrast, he says. “We just used the semantic category information.”

Indeed, given the richness of the dreaming experience, such visual qualities may well be encoded during sleep. “Your brain creates a whole virtual world for you when you are dreaming, complete with characters, settings, interactions, dialogues,” says Zadra. “But you’re actually in your bed asleep; there is no visual input. So your brain is literally creating this virtual world from A to Z.”

REM sleep enhances emotional memories

Witnessing a car wreck or encountering a poisonous snake are scenes that become etched in our memories.

But how do we process and store these emotional scenes so that they’re preserved more efficiently than other, more neutral memories?

In a new study published recently in “Frontiers in Integrative Neuroscience,” University of Notre Dame researchers Jessica Payne and Alexis Chambers found that people who experienced rapid eye movement (REM) sleep soon after being presented with an emotionally-charged negative scene — a wrecked car on a street, for example — had superior memory for the emotional object compared to subjects whose sleep was delayed for at least 16 hours. This increased memory for the emotional object corresponded with a diminished memory for the neutral background of the scene, such as the street on which the wrecked car was parked.

These results suggest that the sleeping brain preserves in long-term memory only those scenes that are emotionally salient and aid in adaptation.

“Our results suggest that REM sleep, which has long been thought to play a role in emotional processing and emotional memory, helps us selectively preserve in memory only what is most important and perhaps beneficial to survival,” says Payne, a Notre Dame assistant professor of psychology who specializes in sleep’s impact on memory, creativity and the ability to process new ideas.

We know that emotional events occupy a privileged position in our memories — they shape our personalities, represent defeats and achievements, mark milestones in our lives and often drive anxiety and mood disorders.

This study shows that the sleeping brain doesn’t just consolidate all recently encountered information. It appears to select for consolidation only the most emotional part of the experience, and the evidence suggests that REM sleep critically modulates memory for highly arousing emotional information.

(Image: iStock)

Extended sleep reduces pain sensitivity

A new study suggests that extending nightly sleep in mildly sleepy, healthy adults increases daytime alertness and reduces pain sensitivity.

"Our results suggest the importance of adequate sleep in various chronic pain conditions or in preparation for elective surgical procedures," said Timothy Roehrs, PhD, the study’s principal investigator and lead author. "We were surprised by the magnitude of the reduction in pain sensitivity, when compared to the reduction produced by taking codeine."

The study, appearing in the December issue of the journal SLEEP, involved 18 healthy, pain-free, sleepy volunteers. They were randomly assigned to four nights of either maintaining their habitual sleep time or extending their sleep time by spending 10 hours in bed per night. Objective daytime sleepiness was measured using the multiple sleep latency test (MSLT), and pain sensitivity was assessed using a radiant heat stimulus.

Results show that the extended sleep group slept 1.8 hours more per night than the habitual sleep group. This nightly increase in sleep time during the four experimental nights was correlated with increased daytime alertness, which was associated with less pain sensitivity.

In the extended sleep group, the length of time before participants removed their finger from a radiant heat source increased by 25 percent, reflecting a reduction in pain sensitivity. The authors report that the magnitude of this increase in finger withdrawal latency is greater than the effect found in a previous study of 60 mg of codeine.

According to the authors, this is the first study to show that extended sleep in mildly, chronically sleep deprived volunteers reduces their pain sensitivity. The results, combined with data from previous research, suggest that increased pain sensitivity in sleepy individuals is the result of their underlying sleepiness.

New Treatment for ‘Sleeping Beauty’ Syndrome?

Most of us have experienced it: that dull, dragging semi-conscious state of deadened awareness and desperate urge to nap that comes from sleep deprivation. For people with primary hypersomnia, however, this is the way they go through life, constantly feeling only half-awake but never able to get enough good sleep to arise truly refreshed. Also known as “Sleeping Beauty Syndrome,” the condition leaves those with the worst cases languishing in bed in what seems like the opposite of a fairy tale, without a prince’s kiss to cure them.

But a new study, published in Science Translational Medicine, suggests both a possible cause and a potential treatment for the condition, which may ultimately lead to treatments for other sleep disorders. The origin of primary hypersomnia, which has some genetic components is still unknown, as is the number of people who are affected by it.

One particularly striking form of the disease, Kleine-Levin syndrome, produces such tiredness and sleep-drunkenness that people are unable to attend school or work. In males, it can include hypersexual behavior, compulsive masturbation, a desire for promiscuous sex or making inappropriate sexual advances, all while in a sleepy, semi-conscious state.

In the latest study, researchers led by David Rye of Emory University in Atlanta studied 10 men and 22 women seeking treatment for primary hypersomnia. In the patients’ spinal fluid, the scientists discovered a previously uncharacterized chemical that stimulates the GABA-A receptor. This receptor is best known as the site where sleep-inducing drugs like Valium and Xanax have their effects, since activating GABA-A receptors can result in drowsiness.

The finding suggested a possible treatment. A drug, known as flumanezil can treat Valium and Xanax overdoses or to reverse the effects of related compounds used in anesthesia. Could it block or reverse the effects of the unknown agent that was activating GABA-A receptors in primary hypersomnia?

The authors conducted a brief placebo controlled trial with seven patients—including one with Kleine-Levin symptoms — to find out. Indeed, injections of flumanezil improved the participants’ ability to pay attention and remain alert. One participant has now taken the drug daily for four years. “Although her nightly sleep duration remained at 9 to 10 hours, she nearly always awakened refreshed without an alarm and daytime sleepiness was markedly reduced,” the researchers write.