Sleep enhances emotional memory, preserves emotional intensity

Sleeping on a negative thought helps preserve it, a recent study concluded. Participants were shown images. Some of the images were positive, others negative. Twelve hours later, those who’d been asleep had better recognition of the images. The negative images and the positive ones.

Emotional reaction to the negative images was greatly diminished over time when participants stayed awake. But for people who slept, the reaction to the negative images was just as strong as when they’d first viewed them. Researchers also linked a longer time spent in REM sleep with preserving emotional reactions to the images. The study was unable to connect REM sleep with recognizing the images.

The study was conducted by the Department of Psychology and Neuroscience and Behavior Program at the University of Massachusetts. It appeared in the January issue of The Journal of Neuroscience.

Mid-Life Sleep Changes May Accelerate Cognitive Decline

New research published in the journal SLEEP
shows that middle-aged adults who have negative changes in sleep duration may experience a decline in cognitive function comparable to four to seven years of aging. The findings suggest that poor sleep can accelerate the aging process and lead to dementia at an earlier age.

The study involved more than 5,400 London-based public employees ages 45 to 69. The researchers used a series of questionnaires and tests to examine the participants’ sleep habits and cognitive function over a span of approximately five years.

Results show that the study participants who began sleeping less than six hours per night scored lower on tests for cognitive reasoning, vocabulary and overall cognitive function.

People who moved to sleeping an unusually long amount of hours – more than eight per night – had an even worse outcome. Long-sleepers had lower scores on all of the cognitive function tests except for short-term verbal memory.

The reason why long-sleepers had a worse cognitive outcome is unknown because the study relied on questionnaires to determine sleep length. It’s possible that the subjects who reported more than eight hours had poor quality of sleep due to frequent wakings.

Sleep apnea has been linked to a cognitive decline that is often mistaken for dementia. People with sleep apnea may wake hundreds of times per night without even knowing it. As a result, they may feel tired and “foggy-headed” the next day. Common treatments such as CPAP can reverse the brain tissue damage caused by sleep apnea and reverse cognitive impairment.

A small decline in memory is a normal part of the aging process and is common in much older adults. As the study shows, when found in middle-aged adults, memory problems and overall cognitive decline can be a red flag for sleep apnea or unhealthy sleep habits.

Invest in your long-term health by making six to eight hours per night a priority. If you are still fatigued most mornings you may want to consult a sleep specialist and get tested for sleep apnea or other sleep disorders.

A Solution to Sleep Problems from Post-War Trauma

A new pilot study shows a treatment approach that combines cognitive-behavioral therapy with image rehearsal can help shell-shocked veterans find more peaceful sleep. PTSD affects nearly 1 in 4 veterans who served in either Afghanistan or Iraq. Once they return home, as many as 91 percent of veterans report having trouble falling asleep or staying asleep.

The study involved a group of 22 veterans with sleep problems related to symptoms of post-traumatic stress disorder (PTSD). Half of the veterans received a combination of cognitive-behavioral for insomnia and image rehearsal therapy for PTSD-related nightmares. The control group was assigned prescription drugs including sleeping pills, antidepressants and other mood stabilizers. Both treatments lasted about twelve weeks.

Short term results show the group who received CBT and image rehearsal therapy saw significant improvements in sleep and PTSD symptoms. Due to the sample size and the nature of the pilot study, further research is needed to demonstrate the effectiveness of the approach.

The study was published in the February issue of Journal of Clinical Sleep Medicine, the official journal of the American Academy of Sleep Medicine.

The approach used in the study combines two commonly used treatments for related conditions. Cognitive behavioral therapy is considered the front line treatment for long-term insomnia. And behavioral sleep specialists use image rehearsal therapy to treat nightmare disorder. Both sleep disorders bare similarities to the sleep-related symptoms of PTSD.

Another recent study proposed a more radical treatment for PTSD - sleep avoidance after a traumatic event. The authors theorize the trauma won’t go into memory if you don’t sleep. Sleep after all plays an important role in the development of memories.

Learn more about sleep and memory.

Sleep: Nature’s Study Aid

Get some sleep instead of pulling an all-nighter to buy extra time to cram for a vocabulary exam. A new study found that sleeping after a study session dramatically helps with the recall of new words. This approach can help prospective students improve their performance on the make-or-break tests like the SAT, ACT or GRE.

Two groups of study participants learned a series of new words phonologically similar to familiar words. Both groups were tested after the initial study session. The session occurred in the evening for half of the subjects; the others studied in the morning.

Volunteers who studied in the evening slept before taking a follow-up test in the morning. The people who studied in the morning had to take the second test later in the evening, and were not permitted to sleep.

Results indicate the participants remembered more words when they slept before the follow-up exam. Brain activity data suggests sleep spindles during deep sleep helped the volunteers retain the new words.

In a statement to the media, one of the authors suggested sleep plays an important role in the reorganization of new memories.

Regular may notice studies these findings are in line with several recent studies involving sleep and memory. One noted study involved word association problems commonly found in the SAT. The research concluded that long naps with REM sleep led to higher test scores than short naps or waking rest periods.

Another article published in April reported that naps helped a group of study participants learn the correct path through a complex maze.

The message is clear: sleep on your academic success and shun the caffeine and cram sessions.

REM Sleep Boosts Creative Problem Solving

The sleep stage sometimes characterized by vivid dreams is when your mind goes to work for you. A study presented at the Annual Convention of the American Psychological Association demonstrated how REM sleep can boost memory and creative problem solving.

Sleep researchers at the University of California, San Diego, used a word association test to show the difference REM sleep makes on memory. Participants took the test in the morning and the afternoon, after either a nap with REM sleep, a short nap without REM sleep or a quiet rest period.

The first part of the test resembled SAT word-analogy questions. One sample question was:

Q: Chips:salty::candy:______
A: Sweet

After a 90 minute rest period, the subjects moved onto the second round. That involved using the first round’s answers as a response to three seemingly unrelated words.

Q: cookie: heart: sixteen
A:Sweet

The participants who were allowed REM sleep performed better in the afternoon, while the people who didn’t nap or get any REM sleep saw no improvement.

The authors believe REM sleep helped connect networks of previously unassociated information in the brain, which helped creative problem solving.

The findings are similar another recent study involving dreams and memory. Both results suggest REM sleep is when we pull together all the information from the day and turn it into memory.

Make Plans and Sleep on Them for Memory Boost

If you want to check off more items on that to-do list, your best bet may be to think it over and then get some rest.

A new Washington University study found people are more likely follow through with their plans if they memorize them before bedtime. Study participants who tried to carry out their intentions before sleep had less success.

The memory boost is a sort of “trigger effect.” A situation, place or thing the next day will suddenly remind you of your plans. Sleep strengthens the association between context and intention. Researchers say it doesn’t help the direct connection between the person and the message itself.

A process called prospective memory happens during slow wave, or deep sleep. Researchers believe it involves communication between the hippocampus and cortical regions. The hippocampus reactivates recently learned memories and places them in long-term storage.

The study involved four groups of 24 university students. One of the groups learned a test routine in the evening and returned for the test in the morning.
The group who tested in the morning performed the prospective memory task best in the part of the test that emphasized context.

The memory-boost may be helpful for everyday texts. For people who follow sleep hygiene the planning process seems to be an appealing wind-down activity compared to watching television or using a computer.

Updating Memories to Prevent the Return of Fear

A new study shows that old fear memories can be “updated” to prevent the return of fear. The discovery is promising for the treatment of post-traumatic stress disorder.

"Our results suggest a non-pharmacological, naturalistic approach to more effectively manage emotional memories," study co-author Elizabeth Phelps, PhD, said in a press release.

The researchers used mild wrist shocks to condition participants to fear colored squares. A day later, the memory was reactivated.

Participants were re-exposed to the feared squares. This was followed by extinction training. They were repeatedly exposed to the colored squares without shocks.

The fear response was banished only if extinction training followed soon after the fear reactivation. This “reconsolidation window” appears to last for about six hours after the fear is reactivated.

During this time an old memory can be “rewritten.” It can be updated with non-fearful information.

"Timing may have a more important role in the control of fear than previously appreciated," said Phelps. "Our memory reflects our last retrieval of it rather than an exact account of the original event."

The study also found that the technique had a long-lasting effect. Fear responses were no longer expressed when tested one year later.

The AASM reports that recurring nightmares tend to be most disturbing aspect of PTSD. In these dreams the event may be relived in a way that seems shockingly real.

Earlier this year the Sleep Education Blog reported that playing the computer game Tetris can reduce unwanted “flashbacks.” Last month the blog noted that imagery rehearsal therapy is helping some people change their nightmares.

Learn more about sleep and memory.

Image by Stu Mayhew

Sleep, Performance & Mental Practice

A new study examined how sleep enhances physical performance following mental practice. The results were published Dec. 1 in the journal Sleep.

The French study involved 32 healthy volunteers. They were between the ages of 20 and 35 years.

The volunteers were trained to perform a computerized finger-tapping task. First they memorized a sequence of eight finger movements.

Then they repeatedly tapped the sequence on a computer keyboard during 30-second periods. The goal was to be as fast and accurate as possible.

The authors reported that previous studies have used this task to show delayed gains in performance after a night of sleep. As a result some researchers recommend that physical practice should be followed by sleep to enhance a newly learned motor skill.

For this study some volunteers physically practiced the finger sequence. Others practiced it using motor imagery, a form of mental practice.

These participants only simulated the action in their mind. They perceived the sensations of how it feels to perform the action. But they didn’t practice the actual finger movements.

Performance was tested right after the 8 p.m. training session. It was retested at 8 a.m. after practice and an eight-hour night of sleep.

As a control, one group was tested after motor imagery practice and no sleep. They were trained at 8 a.m. and retested the same day at 8 p.m.

Results show “offline gains” in performance after a night of sleep for both practice groups. Their speed and accuracy improved. In contrast, the “no sleep” group was slower and made more errors during the retest session.

The results indicate that sleep contributes to the consolidation of motor learning acquired through motor imagery. They also support the principle of “functional equivalence” between mental practice and physical practice.

The authors suggest that motor imagery practice could be included during physical therapy and rehabilitation. For the maximum benefit this practice should be performed before a period of sleep.

Last month the Sleep Education Blog reported that sleep can improve skills that have been learned through observation. Learn more about sleep and memory.

Sleep & Memory: Sleeping “Soundly”

A new study examined how sounds affect memory consolidation during sleep.

Participants were taught to associate 50 images with a random location on a computer screen. Each object was paired with a corresponding sound.

About 45 minutes later they took a nap of 90 minutes or less. This was long enough to enter deep, slow-wave sleep. But they didn’t nap long enough to enter rapid eye movement sleep – or REM sleep.

Twenty-five of the sounds were replayed as they slept. Participants were unaware of the sounds. Then they were tested again after waking from the nap.

Results suggest that the sounds improved their memory. Their performance was more accurate for the 25 objects that had been reinforced by sounds as they slept.

"The research strongly suggests that we don't shut down our minds during deep sleep," lead author John Rudoy said in a Northwestern University news release. "Rather this is an important time for consolidating memories."

Senior author Ken Paller told the New York Times that the method probably isn’t useful for teaching new information. But it may reinforce what you’ve already learned.

“One of our speculations is that SAT scores could be improved,” he said. He added that the technique might be able to help football players learn a playbook.

Recently the Sleep Education Blog reported that what you smell during sleep can affect your dreams. Learn more about sleep and memory.

Sleep & Observational Learning

Sleep enhances the performance of motor skills that have been learned through physical practice. Can it also improve skills that have been learned through observation?

A new study involved 64 healthy people. They were shown a video of a hand performing a finger-tapping task, reports the LA Times.

They were only allowed to watch; they couldn’t practice the movements. EMG monitoring verified the absence of hand muscle movements during observation.

Some participants slept right after the observation period; others slept after a delay of more than 12 hours. Then they were asked to perform the finger-tapping task.

Results show that immediate sleep is necessary for the enhancement of a motor skill through prior observation. There was no performance benefit when sleep occurred more than 12 hours after observation.

Sleeping right after observation improved performance speed by 22 percent; it also reduced the error rate by 42 percent.

The authors conclude that people can transfer observational learning into physical movements without practice. But an “early sleep window” is required to consolidate the procedural memory.

They suggest that this learning method could help athletes or children master new motor skills. It also could help people who have to relearn skills after a stroke or injury.

Image by Bernardo Borghetti

Sleep Deprivation: A Memory-Enhancing Drug?

Researchers report that they have identified the molecular mechanism by which sleep deprivation causes memory problems. They also suggest that drug treatment may be able to prevent the cognitive effects of sleep deprivation.

Their letter was published today in the journal Nature.

“Millions of people around the world suffer from a lack of sleep,” study co-author George S. Baillie said in a University of Glasgow news release. “This research opens the door for effective treatment of the memory loss associated with this debilitating condition."

The research team studied mice that had been deprived of sleep for five hours, reports NatureNews. They detected increased levels and activity of the “PDE4” enzyme in sleepy mice.

Then they treated sleep-deprived mice with the drug rolipram. It is a PDE4 inhibitor. The treatment prevented memory deficits that normally would have appeared after sleep deprivation.

Study co-author Christopher G. Vecsey cautioned that drugs like rolipram do have side effects. He also said that the study targets only one of the negative effects that sleep deprivation can have on the brain.

Study co-author Miles D. Houslay noted that sleep deprivation has many causes.

“People suffer sleep loss not only from disease but also jet lag, looking after young babies, getting old and through types of lifestyle,” he said. “This discovery offers hope for a simple and effective treatment.”

But sleep specialist Dr. Neil Stanley expressed concerns about the potential treatment. He worries that some people may take a drug for sleep loss when lifestyle changes would be a better solution.

“We really need to be thinking about ways to achieve adequate sleep in the first place - not how to deal with the consequences," Stanley told BBC News.

"We are always going to need drugs for people with serious disorders,” Stanley added. “But we don't want to end up medicalising lifestyles. We need to go back to basics and think about the way we as a society lead our lives, and the impact this has on our sleep, rather than looking for a cure."

In March the Sleep Education Blog reported on concerns that many healthy people are taking some medications as “smart drugs.” Learn more about sleep deprivation, and sleep and memory.

Sleep & Memory: Can a Nasal Spray Help You Remember?

German researchers have tested how a unique nasal spray affects sleep and memory.

The study involved a nasal spray containing “interleukin-6.” IL-6 is a cytokine; it is a signaling molecule that transmits information between cells.

Seventeen young men spent two nights in a lab, reports a FASEB Journal statement. Each time they read either an emotional or neutral short story. Then they were given either the IL-6 nasal spray or a placebo spray.

Declarative memory was tested in the morning after a night of sleep. Participants wrote down as many words as they could remember from the story.

Results show that IL-6 distinctly improved the sleep-related consolidation of emotional text material; participants who received the dose of IL-6 could remember more words from the emotional story.

The authors report that this type of memory consolidation benefits mostly from sleep in the second half of the night. This is when REM sleep dominates the sleep cycle.

A 2007 study in the journal Sleep found a link between IL-6 and REM sleep; higher IL-6 levels were independently associated with a longer latency to REM sleep.

A study abstract presented at SLEEP 2009 examined sleep and emotional memory; it suggested that sleep preserves in long-term memory only what is emotionally important and relevant to future goals.

The study found that emotional items are selectively remembered both 24 hours and four months later; but these memories are retained only if sleep comes soon after learning.

Learn more about sleep and memory.

Sleep Reduces False Memories

A new study shows that sleep may improve the accuracy of your memory. Lead author Kimberly Fenn said that this is the first study to examine sleep and memory errors.

The research involved college students who studied lists of words; 12 hours later they were tested. From a list with new words mixed in, they had to identify words that they had studied 12 hours earlier.

Some students studied the original word list at 10 a.m.; they were tested at 10 p.m. after spending the day awake. Other students studied the words at night; they were tested in the morning after at least six hours of sleep.

Results show that false recognition of non-studied words was reduced after sleep; there was no change in correct recognition of studied words.

“It’s easy to muddle things in your mind,” Fenn said in a Michigan State University news release. “This research suggests that after sleep you’re better able to tease apart the incorrect aspect of that memory.”

How does this process work? Fenn suggested that sleep may strengthen the source of a memory. Or a long period of wakefulness may hinder your ability to remember; your memories may be confused with other information that you gathered while awake.

In a video statement Fenn added that the findings could be important for students. After a full night of sleep you might be more likely to pick out the wrong answers on a multiple-choice test.

Sleep also could help you take medications safely; you might be less likely to confuse medications or have a false memory of taking them.

A recent article in the New Zealand Herald examined the impact of false memories on the legal system. It reports that eyewitness error is a factor in 75 percent of wrongful convictions in the U.S.

The article suggests that false memories are easily created. These false memories can be powerful; people with false memories tend to have absolute confidence that they are right.

Learn more about sleep and memory.

Sleep & Long-Term Memory: A “Sharp” Discovery

Researchers report that they have discovered how sleep plays a role in memory consolidation.

The process involves “sharp wave ripples.” These are short, intense, compressed oscillations in the brain; they occur during the sleep stage of slow-wave sleep.

The research team suggests that these events are responsible for consolidating memory. The sharp wave ripples transfer learned information to the brain region where long-term memories are stored.

“This specific brain pattern is the cause behind long-term memory formation,” study co-author György Buzsáki said in a Rutgers news release.

Buzsáki explained that the sharp wave ripples “teach” the brain to form a long-term memory. The ripples occur hundreds to thousands of times during sleep; this helps explain how a momentary event can be ingrained in the memory for a lifetime.

The finding may aid the development of effective treatments for memory disorders.

Learn more about sleep and memory.

Sleep & Memory: “Replay” to Remember

A study published yesterday reports that the role of sleep in memory consolidation has been confirmed.

The study involved mice that ran a maze and then slept. Electrodes monitored their brain activity. While awake the brains of the mice “mapped” the pattern of the maze. Results show that their brains “replayed” this pattern during slow-wave sleep.

"Ours is the first study to demonstrate this link between memory replay and memory consolidation,” study co-author Susumu Tonegawa said in an MIT statement. “The sleeping brain must replay experiences like video clips before they are transformed from short-term into long-term memories."

The study identified a specific circuit in the brain that is involved in this process - the “trisynaptic pathway.” It is located in the “hippocampus.” This is a complex brain structure that is shaped like a seahorse.

In some of the mice the trisynaptic pathway was blocked. This impaired the replay process during sleep. Only mice with a functioning trisynaptic pathway were able to form long-term memories of the maze.

"We demonstrated that this pathway is crucial for the transformation of a recent memory, formed within a day, to a remote memory that still exists at least six weeks later," Tonegawa said.

Read more about sleep and memory on the Sleep Education Blog. Learn more about the stages of sleep on SleepEducation.com.

Sleep & Memory: “That Face Looks Familiar”

Studies show that there is a strong link between sleep and memory. A new study even examines how sleep affects memory for face identity. Does sleep help you recognize a familiar face?

The study involved 112 volunteers; their average age was 25 years. Each participant was shown 60 computer-generated faces in random order.

The heads were bald, and the faces had no unique features such as a mole or a scar. Each face was shown on a computer screen for two seconds at a time. The entire set of faces was shown five times.

Recognition was tested after varying periods of time. Some people were tested after getting sleep; others were tested before getting any sleep. Sixty faces were shown; 30 faces had been seen earlier, and 30 were new faces that had never been seen before.

The results do not show that sleep enhances memory strength. But they do suggest that time spent awake during the retention period impairs memory for face identity.

Wakefulness of 12 hours or more had a detrimental impact on recognition memory strength; it made participants less likely to feel familiar with a test face.

The authors suggest that ongoing sensory stimulation when awake may interfere with visual memory. Sleep may not actively enhance visual memory; but it may temporarily prevent memory loss by “sheltering” visual memory from interference.

Read the full text of the study online.

Sleep and Memory: Remembering & Forgetting

A new article in Newsweek provides an overview of how “sleeping on it” improves memory.

Forming memories. Consolidating memories. Making connections between memories. Sleep appears to play an important role in all these processes.

Another Newsweek article examines whether or not we can learn to forget. New research shows that memory “reconsolidation” may be possible.

Being able to change long-term memories could have practical benefits. In particular it could aid people who suffer from post-traumatic stress disorder.

Nightmares tend to be the most disturbing feature of PTSD. Most people with PTSD also report having disturbed sleep.

Finally, Newsweek offers an online memory Q&A. Find answers to some of the most common questions about memory.

Sleep and Memory: Survival of the Fittest?

An article in the April issue of The Scientist takes an in-depth look at a new theory about sleep and memory.

The theory proposes that sleep’s core function is to prune the synapses formed when you are awake. Only the strongest neuronal connections “survive.”

Thus the most important connections remain; unimportant connections are eliminated. This pruning process boosts learning and memory.

The article addresses a number of questions about the theory.

Will it replace the theory that the purpose of sleep is to replay memories and “consolidate” them? What role does slow-wave sleep play in this process? What about rapid eye movement (REM) sleep? And where do memory patterns fit in – are specific memories reactivated and reorganized during sleep?

Also, how does the theory align with another study published in February? That study suggests that sleep strengthens connections instead of weakening them.

Read the article to find out more.

Why Do We Sleep?

An article from the University of Wisconsin takes a closer look at one of the research teams that just published a new study on sleep and memory.

It explains how their research is taking the study of sleep and memory in new directions. It also examines the question that lies at the foundation of their research: Why?

Why do we sleep? It’s a simple question. And progress is being made to answer it. But definitive answers remain elusive.

“Why is it that the brain cells need to sleep?” researcher Chiara Cirelli said in the article. “That’s really what we are trying to understand.”

Cirelli and colleague Giulio Tononi probed this question last fall in the essay “Is sleep essential?” They conclude that there is still no consensus for “the elusive phoenix of sleep.”

Emmanuel Mignot explored this “unsolved mystery” last year in “Why we sleep: the temporal organization of recovery.” He concludes that it is still unclear why sleep is required. But “recent work suggests multiple roles.”

And Jerome Siegel addressed the topic in the 2003 article “Why we sleep.” He writes that “we have no comparably straightforward explanation for sleep.” But sleep research has led to numerous “reasonable proposals.”

A group from Spain offered a more controversial perspective in the 2007 article “The trivial function of sleep.” They argue that “sleep does not provide additional advantages over simple rest.”

So why do we sleep? Researchers are exploring complex answers to this simple question. And the debate is sure to continue.

Sleep & Memory: Lessons from Fruit Flies

Two new studies in the journal Science use fruit flies to examine the link between sleep and memory.

One study shows that the connections between nerve cells in the brain increase during the day. Then these “synapses” decline during sleep. This reduction of synapses is prevented by sleep deprivation.

This suggests that sleep may “prune” less important connections. This may create space for the brain to store more important memories.

Author Paul Shaw said in a statement that these results have practical implications.

“These data suggest the best thing you can do to make sure you stay sharp…is to make getting enough sleep a top priority," he said.

Another study used three-dimensional photos to look at protein levels in the brains of fruit flies. It focused on proteins that carry messages in the synapses between neurons.

These protein levels dropped by 30 percent to 40 percent during sleep. But the same proteins accumulated in the brains of fruit flies that were deprived of sleep by a “fly agitator.”

This suggests that sleep “resets” the brain. It empties the junk mail from the previous day. This prepares the brain for more learning the next day.

"Much of what we learn in a day, we don't really need to remember," author Chiara Cirelli said in a statement. "If you've used up all the space, you can't learn more before you clean out the junk that is filling up your brain."

But can we really learn about ourselves by studying fruit flies? Why are they useful study subjects? And how do we study them anyway?

A TIME article provides some useful insights. Fruit flies are simple enough to study. But with a genome that has 14,000 genes, they are more complex than you may think.