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Brain Activities During Deep Sleep

Story at-a-glance -

  • Your brain doesn’t simply “turn off” while you’re sleeping; it goes through periods of deep sleep and activity – activity levels similar to those that occur when you’re awake
  • Using an electroencephalogram (EEG) to record brain activity, researchers found that subjects’ brain activity continued to respond accurately to the test questions, albeit at a slower pace
  • Your brain can correctly classify words even while you’re asleep

Some Things You Can Do in Your Sleep, Literally

December 11, 2014 | 92,741 views

By Dr. Mercola

Why do we sleep? And, for that matter, why do all mammals, birds, and reptiles require sleep on a regular basis in order to function? It’s a question that been intensively studied with no definitive answers… except that we know it’s vital to survival.

In people carrying the gene for fatal familial insomnia (FFI), a damaged thalamus (which is located in your brain) makes it impossible to sleep. First, the ability to nap disappears, then it becomes increasingly difficult to sleep at night, progressing over the course of a year until, eventually, it kills you.

In a healthy person, however, it’s estimated that you might be able to survive for two to 10 years without sleep before dying,1 but the consequences it would have on your ability to function would be another story.

It’s known that sleep is crucial for your brain, and that your brain doesn’t simply “turn off” while you’re sleeping. Instead, it goes through periods of deep sleep and activity – activity levels similar to those that occur when you’re awake.

You Can Follow Instructions, Classify Items, in Your Sleep

Sleeping leads to a loss of sensory awareness and an inability to interact with your environment, but your brain is still very much aware, according to new research. The study gave a word test to participants while they were awake and again after they had fallen asleep.

Using an electroencephalogram (EEG) to record brain activity, they found that the subjects’ brain activity continued to respond accurately to the test questions, correctly classifying words, albeit at a slower pace. While the people remained motionless and unaware, their brains were performing complex tasks.

So even if you’re asleep, your brain is likely still awake, which may explain why noises you’re conditioned to respond to – such as the sound of your name or alarm clock – wake you up easily while other noises do not.

The researchers are hoping the finding might lead to more discoveries of what your brain is capable of during sleep – presumably so you could then use your sleeping time in a productive manner… but this is misleading, because sleep is quite possibly among the most productive times of the day, at least as far as your health is concerned.

Your Brain’s Waste-Flushing System Is 10 Times More Active When You’re Sleeping

After you drift off to sleep, your body gets to work repairing and restoring itself. Among the leading theories on why we sleep is that it’s a vial time to recuperate from the damage of daily living. As the Huffington Post reported:2

There's substantive supporting evidence, according to Harvard Medical School, in the facts that ‘many of the major restorative functions in the body like muscle growth, tissue repair, protein synthesis, and growth hormone release occur mostly, or in some cases only, during sleep.’"

Consider, for instance, that repair cells in your brain double during sleep,3 while your brain’s glymphatic system, which helps to flush out waste, is about 10 times more active when you’re sleeping.4

During sleep, your brain cells actually shrink to facilitate the removal of more waste, and removing these “byproducts of neural activity” may be a key reason why sleep is so restorative. Study researcher Maiken Nedergaard, M.D., D.M.Sc., the co-director of the University of Rochester's Center for Translational Neuromedicine, said:5

"The brain only has limited energy at its disposal and it appears that it must [choose] between two different functional states -- awake and aware or asleep and cleaning up… You can think of it like having a house party. You can either entertain the guests or clean up the house, but you can't really do both at the same time."

Other Fascinating Benefits That Take Place While You Sleep

There are many theories for why we sleep, but while many are plausible they fail to explain the whole picture. For instance, theories include that we sleep to:6

  • Stay inactive during times we’re at risk of predation (by staying still, predators cannot see you as easily; critics argue that sleep makes you most vulnerable of all)
  • Conserve energy (including in your brain)
  • Maximize efficiency (such as in animals that sleep much of the day to conserve calories)
  • Boost brain power and learning
  • Repair and restore your body and mind

There are likely many biological reasons why we need sleep. Brain detoxification is only one important process that occurs during this time. Others that we know of include:7

  • Reduction of fears
  • Memory consolidation and strengthening
  • Repair and growth of brain cells

What Happens When You’re Sleep Deprived?

Research tells us that lack of sleep can contribute to everything from diabetes, obesity, and heart disease to physical aches and pains and irreversible brain damage.

In one animal study, sleep-deprived mice lost 25 percent of the neurons located in their locus coeruleus, a nucleus in the brainstem associated with wakefulness and cognitive processes.8 The research also showed that "catching up" on sleep on the weekend will not prevent this damage.

Other research published in the journal Neurobiology of Aging suggests that people with chronic sleep problems may develop Alzheimer's disease sooner than those who sleep well.9

And other research shows that sleeping less than six hours per night more than triples your risk of high blood pressure, and women who get less than four hours of shut-eye per night double their chances of dying from heart disease.10

What makes sleep deprivation so detrimental is that it doesn’t just impact one aspect of your health… it impacts many. Among them are three major risks to your mental and physical well-being:11

  1. Reaction Time Slows: When you’re sleep-deprived, you’re not going to react as quickly as you normally would, making driving or other potentially dangerous activities, like using power tools, risky. One study even found that sleepiness behind the wheel was nearly as dangerous as drinking and driving.12
  2. Your Cognition Suffers: Your ability to think clearly is also dampened by lack of sleep. If you’re sleep-deprived, you will have trouble retaining memories, processing information, and making decisions. This is why it’s so important to get a good night’s sleep prior to important events at work or home.
  3. Emotions Are Heightened: As your reaction time and cognition slows, your emotions will be kicked into high gear. This means that arguments with co-workers or your spouse are likely and you’re probably going to be at fault for blowing things out of proportion.

Meanwhile, previous research has found that sleep deprivation has the same effect on your immune system as physical stress or illness,13 which may help explain why lack of sleep is tied to an increased risk of numerous chronic diseases.

Are You Tired? Try Getting to Sleep Earlier

Since most people have a set time when they must wake up, if you need more sleep the solution is simple: turn off your TV, your cell phone, your computer, and your tablet… and go to sleep early. Try it for a night or two and you might be amazed at how rested you feel.

How do you know if you need more sleep? If you feel tired, it’s a pretty big clue. As William Dement, a co-discoverer of REM sleep and co-founder of the Stanford Sleep Medicine Center, told National Geographic:14

“As far as I know… the only reason we need to sleep that is really, really solid is because we get sleepy.”

Yet, many of us do not listen to our bodies and sleep when we’re tired, and this is a big mistake. For example, when I push myself and don't get high-quality sleep or enough sleep, I'm predisposed to postprandial hypoglycemia. In other words, I have low insulin resistance so when I sleep poorly, it doesn't take much sugar or carbs for it to be easily metabolized and drop my blood sugar—which also makes me really sleepy. When I get enough sleep, I'm far less susceptible to it.

Dr. Rubin Naiman’s -- a clinical psychologist, author, teacher, and the leader in integrative medicine approaches to sleep and dreams -- recommendation is to simply sleep "enough hours so that your energy is sustained through the day without artificial stimulation, with the exception of a daytime nap," which he believes you are biologically programmed for. It’s also said that if you fall asleep within a few minutes of your head hitting the pillow, you’re probably sleep deprived.

A well-rested person will take about 10-15 minutes to fall asleep at night.15 If you’re well rested, you’ll also probably wake up on your own without the need for an alarm clock.

My Top ‘Secrets’ for a Good Night’s Sleep

Making small adjustments to your daily routine and sleeping area can go a long way to ensure uninterrupted, restful sleep and, thereby, better health. I suggest you read through my full set of 33 healthy sleep guidelines for all of the details, but to start, consider implementing the following changes:

  • Avoid watching TV or using your computer in the evening, at least an hour or so before going to bed. These devices emit blue light, which tricks your brain into thinking it's still daytime. Normally, your brain starts secreting melatonin between 9 pm and 10 pm, and these devices emit light that may stifle that process. Even the American Medical Association now states:16
  • “…nighttime electric light can disrupt circadian rhythms in humans and documents the rapidly advancing understanding from basic science of how disruption of circadian rhythmicity affects aspects of physiology with direct links to human health, such as cell cycle regulation, DNA damage response, and metabolism.”

  • Make sure you get BRIGHT sun exposure regularly. Your pineal gland produces melatonin roughly in approximation to the contrast of bright sun exposure in the day and complete darkness at night. If you are in darkness all day long, it can't appreciate the difference and will not optimize your melatonin production.
  • Sleep in complete darkness, or as close to it as possible. Even the slightest bit of light in your bedroom can disrupt your body’s clock and your pineal gland's melatonin production. Even the tiniest glow from your clock radio could be interfering with your sleep, so cover your radio up at night or get rid of it altogether. Move all electrical devices at least three feet away from your bed. You may want to cover your windows with drapes or blackout shades.
  • Install a low-wattage yellow, orange, or red light bulb if you need a source of light for navigation at night. Light in these bandwidths does not shut down melatonin production in the way that white and blue bandwidth light does. Salt lamps are handy for this purpose. You can also download a free application called F.lux that automatically dims your monitor or screens.17
  • Keep the temperature in your bedroom no higher than 70°F. Many people keep their homes too warm (particularly their upstairs bedrooms). Studies show that the optimal room temperature for sleep is between 60 to 68°F.
  • Take a hot bath 90 to 120 minutes before bedtime. This increases your core body temperature, and when you get out of the bath it abruptly drops, signaling your body that you are ready to sleep.
  • Avoid using loud alarm clocks. Being jolted awake each morning can be very stressful. If you are regularly getting enough sleep, you might not even need an alarm.
  • Get some sun in the morning, if possible. Your circadian system needs bright light to reset itself. Ten to 15 minutes of morning sunlight will send a strong message to your internal clock that day has arrived, making it less likely to be confused by weaker light signals during the night. More sunlight exposure is required as you age.
  • Be mindful of electromagnetic fields (EMFs) in your bedroom. EMFs can disrupt your pineal gland and its melatonin production, and may have other negative biological effects as well. A gauss meter is required if you want to measure EMF levels in various areas of your home. Ideally, you should turn off any wireless router while you are sleeping. You don’t need the Internet on when you are asleep.

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