We need to sleep to unburden ourselves of an excessive strengthening of neural connections.
MADISON – Most people know it from experience: After so many hours of being awake, your brain feels unable to absorb any more—and several hours of sleep will refresh it.
Now new research from the University of Wisconsin School of Medicine and Public Health clarifies this phenomenon, supporting the idea that sleep plays a critical role in the brain’s ability to change in response to its environment. This ability, called plasticity, is at the heart of learning.
Reporting in the Jan. 20, 2008, online version of Nature Neuroscience, the UW-Madison scientists showed by several measures that synapses — nerve cell connections central to brain plasticity — were very strong when rodents had been awake and weak when they had been asleep.
The new findings reinforce the UW-Madison researchers’ highly-debated hypothesis about the role of sleep. They believe that people sleep so that their synapses can downsize and prepare for a new day and the next round of learning and synaptic strengthening.
The human brain expends up to 80 percent of its energy on synaptic activity, constantly adding and strengthening connections in response to all kinds of stimulation, explains study author Chiara Cirelli, associate professor of psychiatry.
The idea is that we form lots of connections and not all of them matter. Probably if we form similar connections day after day those end up not getting weakened by sleep.
How about a nap after an intense learning exercise to help form memories?
In this new research, which was conducted by researchers at the University of Haifa in cooperation with the Sleep Laboratory at the Sheba Medical Center and researchers from the Department of Psychology at the University of Montreal, it was revealed that a daytime nap changes the course of consolidation in the brain. Two groups of participants in the study practiced a repeated motor activity which consisted of bringing the thumb and a finger together at a specific sequence. The research examined the "how" aspect of memory in the participants' ability to perform the task quickly and in the correct sequence. One of the groups was allowed to nap for an hour and a half after learning the task while the other group stayed awake.
The group that slept in the afternoon showed a distinct improvement in their task performance by that evening, as opposed to the group that stayed awake, which did not exhibit any improvement. Following an entire night's sleep, both groups exhibited the same skill level. "This part of the research showed that a daytime nap speeds up performance improvement in the brain. After a night's sleep the two groups were at the same level, but the group that slept in the afternoon improved much faster than the group that stayed awake," stressed Prof. Karni.
This makes intuitive sense. We form more permanent memories while we sleep. We can get our brain to form memories by falling asleep.
Here is the cool part: If you are going to learn two tasks you might learn more efficiently if you nap after you learn the first task and before you learn the second task.
A second experiment showed that another aspect of memory consolidation is accelerated by sleep. It was previously shown that during the 6-8 hours after completing an effective practice session, the neural process of "how" memory consolidation is susceptible to interference, such that if, for example, one learns or performs a second, different task, one's brain will not be able to successfully remember the first trained task. A third group of participants in the University of Haifa study learned a different thumb-to-finger movement sequence two hours after practicing the first task. As the second task was introduced at the beginning of the 6-8 hour period during which the brain consolidates memories, the second task disturbed the memory consolidation process and this group did not show any improvement in their ability to perform the task, neither in the evening of that day nor on the following morning. However, when a fourth group of participants was allowed a 90 minute nap between learning the first set of movements and the second, they did not show much improvement in the evening, but on the following morning these participants showed a marked improvement of their performance, as if there had been no interference at all.
We need better methods of inducing sleep and in particular for inducing the sleep states where memories get processed.
If I was king one of the things I'd do is abolish Daylight Savings Time (though I'd ban car lock and car alarm horn beeping first). In my view Daylight Savings Time is a manifestation of the modern tendency of humans to try to deny their biological nature. No, we can't just en masse shift our sleep cycles without some cost to be paid. I like it when science produces evidence that confirms my intuitions. Well, here is some scientific evidence for the idea that Daylight Savings Time is a bad idea.
In a large survey, which examined the sleep patterns of 55,000 people in Central Europe, Roenneberg’s group now shows that the timing of sleep on free days follows the seasonal progression of dawn under standard time, but not under DST.
In a second study, they analyzed the timing of sleep and activity for eight weeks around each of the two DST transitions in 50 people, taking into account each individual’s natural clock preferences, or “chronotypes,” ranging from morning larks to night owls. They found that the timing of both sleep and peak activity levels readily adjust to the release from DST in autumn, but that the timing of activity does not adjust to the start of DST in spring, especially in those who like to stay up late and sleep in.
“While we generally think that the time changes enforced by the DST transitions are ‘only an hour,’ they have far more drastic effects if viewed in the context of the circadian clock’s seasonal changes,” Roenneberg said. “This seemingly small hour translates to a repeat of 10 weeks in the annual progression of the relationship between our sleep-wake cycle and dawn—four weeks in spring and six weeks in autumn. In effect, it’s as if the entire population of Germany, for example, is transported to Morocco in spring and back again in autumn.”
Indeed, “after taking the seasonal adjustment into account, our results show that the human circadian clock does not adjust to the DST transition,” Roenneberg said. “This is especially obvious in the late chronotypes in spring when one looks at their daily activity patterns. Essentially, their biological timing stays on standard, winter time, while they have to adjust their social schedules to the advanced clock time throughout the summer.”
A lot of high school kids are probably the ones most in need of escape from what some adults foolishly think is a good idea. Forcing kids to adhere to schedules that make them really sleepy in class is a big waste.
Skimp on the sleep and your emotional control will decay.
Without sleep, the emotional centers of the brain dramatically overreact to negative experiences, reveals a new brain imaging study in the October 23rd issue of Current Biology, a publication of Cell Press. The reason for that hyperactive emotional response in sleep-deprived people stems from a shutdown of the prefrontal lobe—a region that normally keeps emotions under control.
The new study from Harvard Medical School and the University of California, Berkeley is the first to explain, at the neural level, what seems to be a universal phenomenon: that sleep loss leads to emotionally irrational behavior, according to the researchers. The findings might also offer some insight into the clinical connection between sleep disruptions and psychiatric disorders.
Have a hard time controlling your emotions? Get enough sleep. You can't afford to cut corners on your sleep.
Maybe people become more primitive when they lack sleep.
In the new study, Walker’s team assigned 26 healthy people to either a sleep-deprivation group—in which participants were kept awake for about 35 hours—or a normal sleep group. On the following day, the study subjects’ brains were scanned by functional magnetic resonance imaging (fMRI), which measures brain activity on the basis of blood flow, while viewing 100 images. The images were at first emotionally neutral, but became increasingly aversive over time.
“We had predicted a potential increase in the emotional reaction from the brain [in people deprived of sleep], but the size of the increase truly surprised us,” Walker said of the study’s findings. “The emotional centers of the brain were over 60% more reactive under conditions of sleep deprivation than in subjects who had obtained a normal night of sleep. It is almost as though, without sleep, the brain reverts back to a more primitive pattern of activity, becoming unable to put emotional experiences into context and produce controlled, appropriate responses.
Do we have free will? At best the extent of our free will varies as a function of how much sleep we get, whether we take steroids (roid rage), and countless other influences.
If you are prone to depression don't work the late night shift.
WESTCHESTER, Ill. -- People who work rotating shifts have significantly lower levels of serotonin, a hormone and neurotransmitter in the central nervous system believed to play an important role in the regulation of sleep, according to a study published in the August 1st issue of the journal SLEEP.
Heard of anti-depressant drugs like Prozac, Celexa, Lexapro, Zoloft, or Paxil? They are all selective serotonin reuptake inhibitors (SSRIs). They work by preventing neurons from pulling serotonin back onto the internal side of neural cell membranes. That leaves more serotonin to bind to receptors which boosts certain types of neural signalling which somehow lifts people out of depression. But if you do something that lowers the amount of serotonin available (and working the night shift does this) then you are going to be more prone to depression.
Night shift workers are probably not asking for enough additional compensation to make it worth the effect on their bodies.
The study, authored by Carlos J. Pirola, PhD, of the Universidad de Buenos Aires, Argentina, focused on 683 men of self-reported European ancestry, in which 437 day workers were compared with 246 rotating shift workers. Day and night work periods started at 6 a.m. and 6 p.m. respectively. None of the subjects interchanged their job schedule.
The results showed that serotonin content differed greatly between day workers and rotating shift workers, with levels of serotonin significantly higher in day workers.
“These findings may be important not only to understand the mechanisms related to the circadian rhythm desynchronization imposed by the rotating shift work regime, but also to target truly effective therapeutic strategies that may ameliorate the associated comorbidities and behavioral problems in rotating shift workers,” said Pirola.
In addition to sleep problems, low levels of serotonin are also associated with other conditions such as anger, depression and anxiety.
What would be interesting follow-up experiments: Can high intensity lights, melatonin, or some other treatment or style of living allow people to work late shifts without lowered serotonin? Also, is some fraction of the populace able to do late shift work without getting lowered levels of serotonin?
Now, Giulio Tononi, a professor of psychiatry at the University of Wisconsin-Madison School of Medicine and Public Health, has discovered how to stimulate brain waves that characterize the deepest stage of sleep. The discovery could open a new window into the role of sleep in keeping humans healthy, happy and able to learn.
Tononi figured out how to use transcranial magnetic stimulation above a particular spot to induce the slow wave state of sleeping.
During slow wave activity, which occupies about 80 percent of sleeping hours, waves of electrical activity wash across the brain, roughly once a second, 1,000 times a night. In a paper being published this week in the Early Edition of the scientific journal PNAS, Tononi and colleagues, including Marcello Massimini, also of the UW-Madison School of Medicine and Public Health, described the use of transcranial magnetic stimulation (TMS) to initiate slow waves in sleeping volunteers. The researchers recorded brain electrical activity with an electroencephalograph (EEG).
A TMS instrument sends a harmless magnetic signal through the scalp and skull and into the brain, where it activates electrical impulses. In response to each burst of magnetism, the subjects' brains immediately produced slow waves typical of deep sleep, Tononi says. "With a single pulse, we were able to induce a wave that looks identical to the waves the brain makes normally during sleep."
The researchers have learned to locate the TMS device above a specific part of the brain, where it causes slow waves that travel throughout the brain. "We don't know why, but this is a very good place to evoke big waves that clearly travel through every part of the brain," Tononi says.
Tononi is going to use this capability to investigate his hypothesis that the slow wave state allows the brain to weaken connections that formed from events experienced during the day. He sees sleep as something that weakens many unimportant memories so that our brains do not become burdened with too many memories.
Montreal, October 2, 2006 -- A new study at the Université de Montréal has concluded that people drinking coffee to get through a night shift or a night of studying will strongly hurt their recovery sleep the next day. The study published in the current issue of Neuropsychopharmacology was conducted by Dr. Julie Carrier from the Department of Psychology at the Université de Montréal. Dr. Carrier runs the Chronobiology Laboratory at the Hôpital du Sacré-Coeur de Montréal.
"We already knew that caffeine has important effects on nocturnal sleep. It increases the time taken to fall asleep, it increases the amount of awakenings, and it decreases the amount of deep sleep. We have shown that these effects of caffeine on sleep are way stronger when taken at night prior to a daytime recovery sleep episode than in the evening before a nocturnal sleep episode."
"Caffeine makes daytime sleep episodes too shallow to override the signal from the biological clock that tells the body it should be awake at this time of day," explains Dr. Carrier. "We often use coffee and other sources of caffeine during the nighttime to counteract sleepiness generated by sleep deprivation, jet lag, and shift-work. However, this habit may have important effects when you then try to recuperate during daytime."
Thirty-four moderate caffeine consumers participated in both caffeine (200 mg) and placebo (lactose) conditions in a double-blind crossover design. Seventeen subjects followed their habitual sleep–wake cycle and slept in the laboratory during the night (Night), while 17 subjects were sleep deprived for one night and recovery sleep started in the morning (DayRec). All subjects received a capsule of 100 mg of caffeine (or placebo) 3 hours before bedtime, and the remaining dose 1 hour before bedtime. Compared to placebo, caffeine lengthened sleep latency, increased stage 1, and reduced stage 2 and slow-wave sleep (SWS) in both groups. However, caffeine reduced sleep efficiency more strongly in the DayRec group, and decreased sleep duration and REM sleep only in that group.
People who stay up all night feel the greatest need to use coffee and other sleep-fighting stimulants. But they should most try to avoid use of coffee since they need quality deep sleep when they try to sleep during the day. Sorry about that late night workers.
Also see my posts Scientists Demonstrate Best Way To Use Caffeine and Coffee Drinking Slows Cognitive Decline.
People are known to differ markedly in their response to sleep deprivation, but the biological underpinnings of these differences have remained difficult to identify. Researchers have now found that a genetic difference in a so-called clock gene, PERIOD3, makes some people particularly sensitive to the effects of sleep deprivation. The findings, reported by Antoine Viola, Derk-Jan Dijk, and colleagues at the University of Surrey's Sleep Research Center, appear online this week in the journal Current Biology, published by Cell Press.
There are two variants of the PERIOD3 gene found in the human population, encoding either long or short versions of the corresponding protein. Each individual will possess two copies of the gene, either of which might be the long or short form. Previous work had indicated that the different forms of the gene appear to influence characteristic morning and evening activity levels—for example, "owl" versus "lark" tendencies.
In the new work, a multidisciplinary research team consisting of biological scientists and psychologists compared how individuals possessing only the longer gene variant and those possessing only the shorter one coped with being kept awake for two days, including the intervening night. The researchers found that although some participants struggled to stay awake, others experienced no problems with the task.
The results were most pronounced during the early hours of the morning (between 4 and 8 a.m.), during which individuals with the longer variant of the gene performed very poorly on tests for attention and working memory.
But how do the carriers of the short and long versions perform during the day when they have plenty of sleep?
Carriers of the longer version spent a larger portion of their sleep time in the deepest sleep state. My guess is that confers some sort of advantage. Any idea what that advantage might be?
An additional finding was that the effects of this gene on performance may be mediated by its effects on sleep. When the volunteers were allowed to sleep normally, those possessing only the longer form of the gene spent about 50% more of their time in slow-wave sleep, the deepest form of sleep. Slow-wave sleep is a marker of sleep need, and it is known that carrying a sleep debt makes it very difficult to stay awake and perform at night.
What I'd like to know: Do the people with the longer form of the gene form more memories when they sleep? I ask this because if there are two versions of the gene widespread then likely each version provides advantages and disadvantages. What advantage does the long version provide that compensates for its disadvantages when one stays up all night?
When offspring genetic engineering becomes possible prospective parents are going to be faced with thousands or even tens of thousands of trade-offs between different genetic variations for their offspring. Make your kid a night owl? Or make him wake up at the crack of dawn? Make your kid able to handle lots of sleep disruptions and get by on less sleep? Or perhaps make her brain age more slowly or form more memories per time asleep?
Chronic inflammation is now widely seen as a contributing factor to many diseases of old age. Any dietary or lifestyle choices that increase the amount of inflammation in your body is probably going to accelerate your aging and make you more prone to not just infections but chronic degenerative illnesses such as heart disease and arthritis. With that thought in mind consider that skimping on sleep increases the amount of inflammation in the body.
Researchers at UCLA are the first to show how sleep loss affects the immune system's inflammatory response and suggest sleep interventions as a possible way to address problems associated with inflammation and autoimmune disorders.
Reporting in the Sept. 6 edition of the peer-reviewed journal Archives of Internal Medicine, the research team finds that even modest sleep loss triggers cellular and genetic processes involved in the immune system's inflammatory response to disease and injury.
The findings increase understanding of sleep's role in altering immune cell physiology and suggest sleep interventions as a possible way to address inflammation associated with risk of cardiovascular disease, arthritis, diabetes and other autoimmune disorders.
"This study shows that even a modest loss of sleep for a single night increases inflammation, which is a key factor in the onset of cardiovascular disease and autoimmune disorders such as rheumatoid arthritis." said Dr. Michael Irwin, professor and director of the Cousins Center for Psychoneuroimmunology at the Semel Institute for Neuroscience and Human Behavior at UCLA.
About one-third of the people in the United States have trouble getting a good night's sleep. The problem is more prevalent among people with chronic inflammatory disorders, including heart disease. Epidemiology studies link poor sleep with risk of chronic disease in some people.
Inflammation, with its accompanying redness and swelling, occurs when the immune system floods a diseased or damaged portion of the body with infection-fighting white blood cells that promote healing. However, a variety of immune system disorders can cause the body to turn on itself, sometimes causing inflammation that can damage healthy organs and tissues.
The UCLA research team conducted blood and DNA analyses of 30 healthy adults drawn during the day across three baseline periods and after partial night sleep deprivation. The results show white blood cells called monocytes produce significantly greater amounts of two disease-fighting proteins after a night of sleep loss, compared with amounts found after a night of uninterrupted sleep.
So the dog who insisted I let him out at 4 AM this morning helped accelerate aging. I explained this to him and he was complelely indifferent.
If you can see small changes you can make to your life to up the amount of sleep you get to an adequate amount then make those changes. You'll be better off in the long run.
Update: Does anyone know of scientific research into factors that increase or decrease your need for sleep? For example, if you are doing a lot of mental work and learning during the day does that increase the need for sleep because the mind needs to spend more time processing to form lasting memories of what it learned that day? Or do high fat diets increase the need for sleep as compared to low fat diets? Or does a diet high in vegetables decrease the need for sleep?
A new University of Colorado at Boulder study shows that people who awaken after eight hours of sound sleep have more impaired thinking and memory skills than they do after being deprived of sleep for more than 24 hours.
The study showed test subjects had diminished short-term memory, counting skills and cognitive abilities during the groggy period upon awakening known as sleep inertia, said CU-Boulder Assistant Professor Kenneth Wright, lead study author. The new study has implications for medical, safety and transportation workers who are often called upon to perform critical tasks immediately after waking, since cognitive deficiencies following 24 hours of sleep deprivation have previously been shown to be comparable to the effects of alcohol intoxication, he said.
The study appears in the Jan. 11 issue of the Journal of the American Medical Association. Study authors included Wright and Adam Wertz of CU-Boulder's integrative physiology department and Joseph Ronda and Charles Czeisler of Brigham and Women's Hospital in Boston, which is affiliated with Harvard Medical School.
"This is the first time anyone has quantified the effects of sleep inertia," Wright said. "We found the cognitive skills of test subjects were worse upon awakening than after extended sleep deprivation. For a short period, at least, the effects of sleep inertia may be as bad as or worse than being legally drunk."
Following six nights of monitored sleep lasting eight hours per night, the study participants were given a performance test that involved adding randomly generated, two-digit numbers, said Wright. Based on the results, the researchers concluded the subjects exhibited the most severe impairments from sleep inertia within the first three minutes after awakening, he said.
The most severe effects of sleep inertia generally dissipated within the first 10 minutes, although its effects are often detectable for up to two hours, according to the study authors.
Studies conducted by Dr. Thomas Balkin and colleagues at the Walter Reed Army Institute of Research in Washington, D.C., have shown cortical areas of the brain like the prefrontal cortex take longer to come "on-line" following sleep than other areas of the brain, Wright said. The prefrontal cortex is thought to be responsible for problem solving, emotion and complex thought.
People who have to suddenly do critical work upon waking are prone to making potentially lethal mistakes in those first minutes.
The CU-Boulder study has implications for medical professionals who are often called on to tend patients in crisis on a moment's notice, often at odd hours, Wright said. Medical residents, for example, who may work 80 hours or more per week and who "catnap" at times, could be prone to make simple math mistakes when calculating dosages of medicine during bouts of sleep inertia, he said.
The results also have implications for emergency medical technicians and firefighters who may be hastily awakened and called upon to drive a vehicle to an emergency scene, putting themselves and others at risk, said Wright. The study also has implications for commercial truck drivers, who frequently pause for quick naps in their vehicles' sleeping berths during cross-country excursions, he said.
We should avoid having intellectually difficult problems to solve upon awaking. We should also structure our immediate environments around beds to not require any great cognitive effort to safely navigate.
When I was in grade school and high school I always wanted to stay up later and sleep later than school schedules allowed. My mind was always better later in the day and in the evening. Well, a new study vindicates by feeling at the time that school was not set up for my circadian cycle. Kids are being forced wake up and get going about 2 hours too early.
Current high school start times deprive adolescents of sleep and force students to perform academically in the early morning, a time of day when they are at their worst, according to a study in the June issue of the journal Pediatrics.
Results from high school senior sleep/wake diaries kept for the study also showed that adolescents lost as much as two hours of sleep per night during the school week, but weekend sleep times during the school year were similar to those in summer.
Advanced placement biology students were recruited for the study. So the kids do not sound like they were slackers.
The study was a collaborative project involving researchers at the Feinberg School of Medicine and the Center for Sleep and Circadian Biology at Northwestern University and faculty, students and parents from Evanston Township High School, Evanston, Ill. The students were advanced placement biology students who helped conduct the study and analyze the collected data.
Martha Hansen, advanced placement biology teacher and current science department chair at Evanston Township High School, headed the project in collaboration with Margarita L. Dubocovich, professor of molecular pharmacology and biological chemistry and of psychiatry and behavioral sciences, Feinberg; and Phyllis C. Zee, M.D., professor of neurology, Feinberg.
The study assessed the impact of sleep loss after the start of school on cognitive performance and mood and examined the relationship of weekday to weekend sleep in adolescents.
The study also showed that
exposure to bright light in the morning did not modify students' sleep-wake cycle or improve daytime performance during weekdays probably because of their strict school schedule. All students performed better in the afternoon than in the morning.
Students in early morning classes reported being wearier, less alert and having to expend greater effort. Potential solutions to this problem could be solved by changing school start times and by giving standardized tests later in the day, the authors suggested.For example, classes at Evanston Township High School start at 8:05 a.m. and run until 3:35 p.m. – one of the longest school days in Illinois. Many high schools in the country have start times of 7:15 or 7:30 a.m. In addition, almost all standardized tests in high school begin at 8 a.m.
Since this is when adolescents show their poorest performance levels, a change is clearly needed and would be relatively easy to negotiate, the researchers suggest.
Technology should be used to allow kids to adjust their learning schedules to their body's circadian rhythms. The use of pre-recorded high quality and high resolution lectures would allow kids to watch lectures on difficult subjects when their minds feel keen enough to handle difficult material. Our current regimented method of marching kids through a series of fixed time length classes strikes me as a hold-over from the factory era. Lecture delivery could be done electronically at any time of the day or night. A kid who has a hankering to just listen to hours of biology on one day and hours of history on another day ought to be able to do that as long as all the needed material is viewed. Or if the kid wants to watch physics lectures only after 9 PM then make it easy to do so.
I can even picture electronic methods to detect whether each kid paid attention to n hours of biology lectures and m hours of calculus lectures. Biometric scanning equipment attached to a device that plays lecture videos could track whether each kid has watched each lecture. Or kids could have to set for automatically delivered tests to monitor their progress.
Kids could even win greater flexibility in the use of their time by meeting testing goals. A kid who manage to, say, test as being a month ahead of schedule could be allowed to spend more hours listening to music, watching movies, playing video games, or other activities. We should make education less like a planned regimented socialist economy and give kids ways to earn the ability to exercise greater control of their time. I bet many kids would learn more rapdily and also be happier about learning.
A company called Axon Sleep Research Laboratories has developed a headband alarm clock that awakens you when you are not in a deep stage of sleep.
Have you ever felt that you have had a full night’s sleep, but you still feel tired when your alarm rings? When we sleep, we repeatedly move through several cycles of brain activity. It is incorrectly believed that an extra 15 minutes of sleep would make us feel better. What actually makes us feel alert and energetic, however, is being awoken out of the right sleep cycle.
The scientific community has known about this phenomenon for decades, but the technology has not existed to take advantage of it — until now. Enter SleepSmart: an intelligent alarm clock that monitors your sleep cycles as you sleep, waking you at the ideal moment from the optimal stage of sleep. This optimal moment might be several minutes prior to your set alarm time. However, when you wake up, you will be refreshed and ready for action — just as if you had awoken naturally.
The device is worn on your head and it analyses your EEG brain wave to decide when to awaken you. The device does not appear to be on sale yet.
They claim that being awakened from a lighter stage of sleep will cause a person to feel less tired.
SleepSmart’s technology is based on the existence of sleep cycles. For the sake of simplicity, we will classify the cycles into 3 categories: light, deep and REM (rapid eye movement) sleep. Recent scientific research has learned that the way one feels after waking up is determined not by the length of sleep, but rather the sleep cycle from which that person awakens. When awoken from deep sleep, the sleeper feels groggy, tired, and grumpy. However, if someone wakes up from a lighter stage of sleep, no matter how many hours they slept, they still wake up recharged, invigorated, energetic and alert.
SleepSmart capitalizes on this finding by waking people only from light sleep. In order to do this, users wear a soft headband that passively monitors the brain. The end result is the aversion of sleep inertia and the production of a more energetic, attentive and happy morning.
The headband is the idea of a group of Brown University students.