Posts Tagged ‘Sleep’


May 29, 2016

The Cover Page of the 28 May 2016 New Scientist has SLEEP THE GOOD SLEEP as the title.  According to Matt Walker of he University of California, Berkeley, “sleep has been labelled he this pillar of good health, along with diet, exercise.  But that’s underselling it:  sleep is the foundation on which these other two pillars rest.  There is no tissue within the body and no process within the brain that is not enhanced by sleep, or demonstrably impaired when you don’t get enough.”

Besides the well recognized benefits for memory consolidation, repair and growth sleep—or the lack of it— is now though to have a host of other ill effects.  Too little sleep messes with our emotions and our ability to make sound decisions.  It affects our immune systems and appetites, and has been linked to metabolic diseases such as obesity and type 2 diabetes.  Increasingly, a lack of sleep is implicated in mental health problems to include depression, bipolar disorder, schizophrenia, and neurological conditions such as Alzheimer’s disease.  One of the articles even makes the claim that too much sleep can be harmful, but other articles raise issues that seem to contradict this claim.  One of the reasons for this might be due to genetics and individual differences.

To account for these differences, the best rule of thumb is that we should not need an alarm clock to wake up in the morning.  In other words, we should wake up naturally.

Shift work has bad effects on health.  Unfortunately,  the jobs of many people require shift work.  Quantitative estimates of the damage caused by shift work would be useful for these people in determining whether they should seek different types of employment.  Catching up during weekends for lost sleep, although necessary, does not appear to make up for adverse healthy effects.  The thinking is that the dangers here might be comparable to those incurred via shift work.

Here are the phases of sleep.


REM — 25% of sleep at night.  First occurs about 90 minutes after falling asleep, then every 90 minutes.  These phases get longer later in the night.

STAGE 1 — light sleep.  Happens when we first doze off and just before waking.  Typically lasts for up to 7 minutes.  During this phase we’re prone to twitches, or hypnagogic  jerks.

STAGE 2 — deeper sleep.  Lasts up to about 25 minutes.  Brainwaves become slower and researchers can pick up “sleep spindles,” distinct patterns of brainwaves associated with memory consolidation.

STAGE 3 + 4 — final and deepest stages of non-REM sleep.  heart rate slows.  Lasts up to about 40 minutes.  Brain activity switches to “slow waves.”  Less aware of external noises.  If you’re aroused  from this stage of sleep, it can take up to an hour to become fully alert.

One might conclude from these stages of sleep that napping will not be beneficial.  This is not so.  According to a piece by Catherine de Lange a “nano-nap” lasting just 10 minutes can boost alertness, concentration, and attention for as much as 4 hours.  A “nano-nap”  takes 20 minutes and you increase your powers of memory and recall, too.  We are unlikely  to enter deeper stages of sleep, so we’ll avoid the phenomenon known as sleep inertia, which is the groggy feeling that can occur when waking from deep sleep.

Deep sleep does provide the biggest boost to learning.  Opt for a nap between 60 and 90 minutes, says Walker.  His research shows this aids learning by shifting memories from short-term storage in the brain’s hippocampi to lockdown in the prefrontal cortex, like clearing space on a USB memory stick.   In addition to aiding the retention of factual information, longer naps can increase motor memory, which is useful for training skills such as sport or playing a musical instrument.

A longer nap can also improve equanimity.  When we’re feeling emotional, we should try snoozing for 45 minutes or more.  This should take us through a stage of REM sleep, and brain scans of people following a REM sleep nap showed more positive responses to images and to pleasant experiences.

This post will conclude with statistics that can come in handy when conversations lull.

29 % of people in the US take their cellphones into the bedroom and use it when trying to get sleep (this is not a good idea).

34 minutes is the average extra sleep people get per night after drinking sour cherry juice before bed for 7 days.

67% of the time when men dream about people it’s about other men.  Women dream equally about men and women.

1.2  minutes of sleep is lost per night for each cigarette smoked during the day.

5 is the number of minutes it takes us to fall asleep if were sleep deprived.  The ideal is 10-15 minutes.

100 times an hour:  how often someone with sleep apnea might stop breathing in the night.


Personal Observations on Meditation Techniques in General and the Relaxation Response in Particular

November 3, 2015

Personally I have difficulty in getting comfortable in a chair, much less sitting on a cushion or in some Yoga positions.  I much prefer reclining, that is lying down.  Although I had thought this might be the case it was only in “The Relaxation Response” that I saw the reason, and that is a tendency to fall asleep.  Mental processes while sleeping differ from mental processes while sleeping.  Clearly this is the case or there would be no need to meditate.

However, I would argue that unless one is very tired, it is unlikely that one would fall asleep before the needed ten to twenty minutes of meditation, and surely that pre-sleep time would be beneficial.

Frankly, if I am having difficulty sleeping or have awakened and am having difficulty getting back to sleep, I find that meditation is very useful in getting back to sleep.  After all, meditation quiets the mind and it is a noisy mind that keeps us awake.

I also find that meditating while walking to be extremely useful.  Particularly when one can walk in nature, one experiences the dual benefits of both nature and meditation.

Then there is ad hoc meditation.  This occurs in social, work, or athletic situations when you are stressed.  Try to take a brief break and engage the Relaxation Response to try to de-stress and recenter yourself.  This might well save you from saying or doing something you’ll regret.

The following is from a preceding healthy memory blog post, “A Simple Technique to Spark Mindfulness:”

S – Stop. Simply pause from what you are doing.
T –Take a few slow, deep, breaths with awareness and tune in.
O – Observe and curiously notice your thoughts, feelings, and sensations.
P – Proceed with whatever you were doing with awareness and kindness.

© Douglas Griffith and, 2015. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.

Sleep Time

December 21, 2014

Given that around one-third of our lives is spent sleeping, sleep must be considered for effective time management. I believe it’s a mistake to regard sleeping as wasted time and to work to keep the time we sleep to a minimum. I have a good friend who is quite proud to have gotten it down to four hours per night. I have never been able to understand why this is desirable. For me, sleeping is one of my favorite activities. Apart from being refreshing, I enjoy dreaming. We are able to slip the bounds of reality when we dream.

Levitin in his book The Organized Mind: Thinking Straight in the Age of Information Overload notes other reasons sleep is important. Newly acquired memories are initially unstable and require a process of neural strengthening to become resistant to interference and accessible to us for retrieval. Usually there are a variety of ways that an event can be contextualized. The brain has to toss and turn and analyze the experience after it happens, extracting and sorting information in complex ways.

Recent research has given us a better understanding of the different processes that are accomplished during distinct phases of sleep. New experiences become integrated into a more generalized and hierarchical representation of the outside world. Memory consolidation fine tunes the neural circuits that first encountered the new experience. It has been argued that this occurs when we sleep because otherwise those circuits might be confused with an actually occurring experience. Moreover, all this consolidation does not occur during a single night. Rather, it unfolds over several sequential nights. Sleep that is disrupted even two or three days after an experience can disrupt our memories of it months or years later. Mathew Walker (from UC Berkeley) and Robert Stickgold (frm Harvard Medical School) notes three distinct kinds of information that occur during sleep.

The first is unitization, the combining of discrete elements or chunks of an experience into a unified concept. The second kind of information processing that takes place during sleep is assimilation. The brain integrates new information into the existing network structure of other items in memory. The third process is abstraction where hidden rules are discovered and entered into memory. Across a range of inferences involving not only language but mathematics, logic problems, and spatial reasoning, sleep enhances the formation and understanding of abstract relations to the extent that people often wake having solved a problem that was unsolvable the night before. Levitin writes that this might be part of the reason why young children just learning language sleep so much.

This kind of information consolidation happens all the time, but it happens more intensely for tasks in which we are intensely engaged. If you struggle with a problem for an hour or more during the day in which you have invested your focus, energy, and emotions, the it is ripe for replay and elaboration during sleep.

Sleep is also necessary for cellular housekeeping. Specific metabolic processes in the glymphatic system clear neural pathways of potentially toxic waste products that are produced during waking thought.

Parts of the brain sleep while others do not. Sometimes we are either half-asleep or sleeping only lightly. Sometimes people experience a brain freeze being unable to momentarily to remember something obvious. Should we find ourselves doing something silly, such as putting orange juice on cereal, it might be that part of the brain is asleep.

Levitin likens the sleep-wake cycle to a thermostat. Sleep is governed by neural switches that follow a homeostatic process that are influenced by our circadian rhythm, food intake, blood sugar level, condition of the immune system, stress, sunlight, and darkness. When our homeostats increase above a certain point, it triggers the release of neurohormones that induce sleep. When the homeostat decreases below a certain point, a separate set of neurohormones are released to induce wakefulness.

Our current 6 to 8 hour followed by a 16-18 hour sleep cycle is relatively new according to Levitin. He writes that for most of human history, our ancestors engaged in two rounds of sleep, called segmented or bimodal sleep, in addition to an afternoon nap. The first round of sleep would occur for four or five hours after dinner, followed by an awake period of one of more hours in the middle of the night, followed by a second period of four or five hours sleep. He notes that bimodal sleep appears to be a biological norm that was subverted by the invention of artificial light.. He writes that there is scientific evidence that the bimodal sleep plus nap regime is healthier and promotes greater life satisfaction and efficiency.

Admittedly, it would be difficult for most of us to be able to accommodate this bimodal sleep regime. Do what works for you and fits into your requirements. Do not overlook the beneficial effects of naps, even very short ones. And stay away from sleep medications that can do more harm than good. Should you have difficulty falling asleep, the worst thing you can do is to get upset about it. Relax. Try meditating on a word or phrase. If you have difficulty attending to the phrase, just relax and gently bring your attention back to meditating. If you are having pleasant thoughts or memories, just go with the flow. Remember that parts of the brain might be sleeping while other parts remain awake, so don’t panic. Be patient. You might be getting more sleep that you think you are getting.

In closing, Levitin notes that sleep deprivation is estimated to cost US. businesses more than $150 billion a year in absences, accidents, and lost productivity It’s also associated with increased risk for heart disease, obesity, stroke, and cancer. So sleep is important. Don’t shortchange yourself.. If you have a chronic problem sleeping, seek professional help.

Sleep, the Brain, and Alzheimer’s

November 24, 2013

Sleep has always presented a problem for science. It is an activity in which we humans spend approximately one-third of our lives. So there must be some justification, but what is it? Dreaming is an important area of study. The healthymemory blog has a substantial number of posts on dreaming, which will not be reviewed here (to find them, enter “dreaming” into the search block of the healthymemory blog). Recent research has identified how waste materials are removed from the brain, and how this removal increases when we sleep. A healthymemory blog reader has led me to some of this research and I do thank him for his assistance.

For most of the body there is a complex system of lymphatic vessels that cleanse tissues of potentially harmful metabolic waste products, accumulations of soluble proteins and excess interstitial fluid. Unfortunately, the central nervous system lacks a lymphatic vasculature, so the problem was to identify how waste products are removed from the brain. Research by Maiken Nedergaard and her research group at the University of Rochester has appeared to have solved this problem.1 This finding is especially important as the breakdown of the brain’s innate clearance system might underlie the pathogenesis of neurodegenerative disorders such as Alzheimer’s, Parkinson’s, and Huntington’s disease, as well as ALS and chronic traumatic encephalopathy.

The research team injected fluorescent tracers into the brains of living mice, and then imaged the movement of the tracers using two-photon microscopy in real time. They were able to identify a complete anatomical pathway, which they dubbed the “glymphatic system” due to its dependence on glial cells performing a “lymphatic” cleansing of the brain interstitial fluid. (enter “glial” into the healthymemory blog search block to learn more about glial cells).

“During sleep, the cerbrospinal fluid flushed through the brain very quickly and broadly,” said Rochester neuropharmacologist Lulu Xi/”2. Another experiment revealed that sleep causes the space between cells to increase by 60%, allowing the flow to increase. When the mouse was awakened, the flow in the brain was greatly constrained.

“Brain cells shrink when we sleep, allowing fluid to enter and flush out the brain,” Nedergaard said. “It’s like opening and closing a faucet.”3 The research also found that beta-amyloid protein cleans out of the brain twice as fast in a sleeping rodent as in one who is awake.

This research once again underscores the importance of getting enough sleep. It also suggests that failures in this cleansing system might contribute to neurodegenerative disorders such as Alzheimer’s, Parkinson’s, and Huntington’s disease, as well as ALS and chronic traumatic encephalopathy. So this research opens up new research avenues for studying and, possibly curing or remediating these diseases.

2Kim, M. (2013). During sleep, the brain clears up. The Washington Post, October 20, p. A5.


Sleep and a Healthy Memory

December 12, 2012

The Health & Science Section of the Washington Post included a piece of sleep1. Sleep is so important to a healthy memory that I feel compelled to relay the contents of that article to you. Our brains are active throughout the four stages of sleep, which are:

Stage 1: Falling asleep, which is characterized by Beta waves.

Stage 2: Light sleep, which is characterized by Alpha waves.

Stage 3: Deepest sleep, which is characterized by Theta waves.

Stage 4: Rapid Eye Movement (REM), which is characterized by Delta waves.

Memory and learning is impaired. The hippocampus is critical in transferring information into long term storage. Losing two hours of sleep in a single night can impair this information transfer. REM sleep is especially important because that appears to be when the brain filters out irrelevant information.

Missing a few hours sleep can result in accidents. This can produce “local sleep,” in which parts of the brain nod off while a person is nominally awake. One study found that middle school and high school athletes who slept eight or more hours each night were 60% less likely to be injured playing sports than those who slept less.

People who sleep four hours or less a night spend a lower percentage of time in Stage 2 and REM sleep. Consequently, they feel hungrier, crave more sweet and salty foods, and consume more calories than those who sleep longer. This makes them more susceptible to obesity and diabetes.

A study involving mice found that when Alzheimer’s plaques began to build in their brains, their sleep was disrupted. This suggests that poor sleep might be one of the first signs of the disease. It has also been found that connections between areas of a network in the brain used in daydreaming and introspection are disrupted in people who are chronically sleepy during the day. Alzheimer’s damages the same network, so these shaky connections might signal a susceptibility to the disease.

So, get a good night’s sleep. It is refreshing and will keep your memory healthy.

1Berkowitz B., & Cuadra, A. (2012). The Rest of the Story on Sleep. Washington Post, Health & Science, e2, December 4.

Why Do We Dream?

October 2, 2011

Given that we are asleep about one-third of our lives, and given that dreaming is a predominant part of sleeping, dreaming must be important. Researchers have been working on this problem for many years and an article1 in the New Scientist summarizes some recent research. Changes in electrical activity in the brain and movements of the eyes allow us to identify five stages of sleep. Sleep begins with two stages of light sleep, followed by two stages of deep sleep, followed by a stage of Rapid Eye Movement (REM) sleep. This sleep cycle lasts approximately 90 minutes and is repeated until we awaken.

One of the roles of dreaming is memory consolidation (See the Healthymemory Blog Post, “To Remember It, Sleep on It). There are a substantial number of studies reporting that sleep facilitates memory. The New Scientist article reported a study in which non-REM dreams boost people’s performance on a problem. The research participants were given an hour of training on a complex maze. Some participants were allowed to take a ninety-minute nap, while other participants were kept awake. When tested again on the maze, people who dreamed showed bigger improvements than people who did not dream. The largest improvements were in people who dreamed about the maze. This dream content could be somewhat bizarre. One of the participants who showed the largest improvement reported the following dream: “there were people at checkpoints in the maze as well as bat caves that he had visited a few years earlier.”

REM dreams contain more emotion, more aggression, and more unknown characters than non-REM dreams, whereas non-REM dreams are more likely to involve friendly encounters. A conjecture is that non-REM dreams help us practice friendly encounters, whereas REM dreams help us to rehearse threats. REM sleep strengthens negative emotional memories2 . The notion here is that if we don’t remember bad experiences, we will not learn from them. It is also thought that reliving the upsetting experience in the absence of the hormonal rush that accompanied the actual event helps to strip away the raw emotion from the memory. This is somewhat analogous to desensitization techniques employed by therapists. Although these REM dreams can be helpful for many situations, they do not work for people with Post Traumatic Stress Disorders. This is unfortunate.

So sleep and dreaming are activities that are important to both cognitive and emotional health. Shortchanging yourself of this needed activity has adverse effects on your memory health.

1Young, E. (2011). The I in Dreaming. New Scientist, 12 March, 36-39.

2Cerebral Cortex, vol 19, p.1158

Take a Nap: Sleep is Important for a Healthy Memory

December 5, 2010

A recent article1 in the SharpBrains blog relates a study by Matthew Walker presented at this year’s American Association for the Advancement of Science (AAAS) convention. Young adults were separated into two groups: one that napped and one that didn’t. At noon, both groups performed a learning task. At 2 PM the napping group took a 90 minute nap while the other group remained awake. Then both groups performed more learning tasks. The group that had napped performed better than the group that remained awake.

Readers of the Healthymemory Blog should be familiar with the role of the hippocampus. The hippocampus is critical for learning. These researchers interpreted their findings as supporting the notion that a function of sleep is to clear away all the clutter stored in the hippocampus to make room for new information. Walker said “Sleep is critical to learning. It’s like the brain is a sponge. Sleep wrings certain key regions out so you’re able to soak up new information the next day. It’s as though the e-mail box in your hippocampus is full and, until you sleep and clear out those fact e-mails, you’re not going to receive any more mail. It’s just going to bounce until you sleep and move it to another folder.

We spend about one-third of our lives sleeping. So sleep must serve some important functions. There is much theory and conjecture regarding why we sleep, but experiments such as this one provide empirical evidence. It is well established that sleep is good for you. Getting the appropriate amount of sleep is tied to a better immune system, metabolic control, memory, learning, and emotional functioning.

It is said that pulling an all-nighter the night before an exam can decrease the ability to remember information by about 40 percent. Personally, I worked my way through the entire educational system receiving a Ph.D and I never pulled an all-nighter.

As we get older, we tend to sleep less. Learning proficiency also declines. Walker is interested in investigating whether there is a cause and effect relationship here. It is also interesting to speculate regarding the direction of any cause and effect. If we continue to learn and remain mentally active as we age, will our sleep increase proportionately. Perhaps this observed relationship is due to disengaging from life and new experiences when we age, which results in reduced sleep and perhaps even neurogenerative decline. Remaining mentally active, as advocated by the Healthy Memory Blog, might reduce or eliminate this decline.


© Douglas Griffith and, 2010. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.