While your body and your conscious mind appear to zone out during sleep, your brain is still very active, and doing some amazing things.

Here’s just a few of the things we know are going on during sleep:

Breaking down adenosine build-up

Adenosine is a chemical that that causes drowsiness. It gradually builds up in your blood throughout the day while you are awake, causing you to get sleep towards the end of the day. This build-up is cleared while you sleep. People who don’t give their bodies enough time to completely break down this chemical start the day already drowsy and have a harder time focusing and functioning at peak cognitive levels.

Boosting your immune system

When you are ill, your body craves sleep, often sleeping more than usual. This suggests that sleep may boost the immune system to help you heal or recover from illness. Sleep is also important to maintain a healthy immune system.

Consolidating memories

During sleep, tenuous new neural pathways are reinforced, cross-referenced with existing memories, and consolidated for longer-term storage and retrieval. Persons with sleep disorders often have difficulty remembering events of the day, performing cognitive tasks and learning new skills. A study in rats showed them retracing neural pathways depicting a maze they learned during the day, suggesting that we need sleep to review and reinforce what we’ve learned during the day. Sleep deficits also reduce your ability to perform math problems and think critically. Memory is impaired and it is harder to retrieve information you should know.


Rapid Eye Movement sleep (REM) changes this pattern of slowly descending into lower and lower brain and body activity levels. During REM sleep, your eyes are moving about quickly and your breathing is elevated. You become paralyzed, unable to move your limbs and you begin to dream. While we don’t fully understand everything about sleep yet, it seems to be an important process for restoring your brain and consolidating memories. In fact, people who get too little sleep to enjoy the REM phase often fall asleep during the day and move quickly into REM, suggesting their brain is trying to make up for lost REM time.

In a normal full sleep cycle, we typically spend about two hours dreaming, but science is still trying to understand why we dream and the biological processes that cause dreaming. Most mammals and birds also exhibit REM sleep, so it is likely that they, too, dream. We know that REM is critical to learning because people deprived of REM sleep will not remember something they “learned” the day before. People who get to the REM stage will be able to remember, even if they don’t get a full night’s sleep. Most neuroscientists think that the cerebral cortex is making sense of your day, organizing random signals and tenuous, new neural connections. It is connecting new information to existing information, putting together new memories and strengthening your ability to retrieve them.

Passing through the five stages of sleep

Image credit: tuck.com

Most people pass through a cycle of five stages during sleep.

Stage 1 – Light sleep. We drift in and out of sleep and can be easily awakened. You may see fragmented images moving across your eyelids, perhaps images from the day or from something you’ve been working on.

Stage 2 – Brain waves begin to slow down, except for occasional spikes in activity called spindles.

Stage 3 – Delta waves, which are extremely slow, begin to appear sporadically, mixed in with faster waves. This stage is the beginning of what is called “deep sleep.”

Stage 4 – Delta wave patterns predominate brain activity in this stage. People in stages 3 and 4 are very hard to awaken and may be disoriented when first waking. If you are going to sleepwalk or have a nightmare, it will probably take place during stage four.

The price we pay for plasticity

Another way of looking at it is that sleep is the price we pay for neuroplasticity. The constant coupling and de-coupling of neurons throughout your waking hours allows you to predict future events based on experience, form critical thoughts, learn new skills and interact socially with others. But it takes a lot of energy, and energy creates waste products and toxins. Your brain is running at a high level of performance all day long, producing toxic by-products that must be eliminated before you return to that peak level during the next day. Since most animals also sleep, it suggests that their brains are paying a similar price.

The hippocampus and sleep

It is probably no surprise that the hippocampus, which is very active in learning, is also very active during sleep. While most people associate the hippocampus with spatial relationships, such as London cabbies memorizing the complex web of London streets, it appears to be involved in all types of learning – sort of mapping new information to existing information for us. We’re not sure how the brain decides which memories are worth keeping and which can be tossed, but it seems to do a pretty good job of making that choice for us. Sleep seems to be especially important in forming memories of emotionally charged events, often allowing us to reset our reaction to an upsetting event during sleep, giving us a more positive picture in the morning. It can also help us make a better decision when the stakes are high.

Your circadian rhythm

Your entire body is regulated by a part of your brain called the suprachiasmatic nucleus (SCN), where two bundles of neurons process signals from the optic nerve to other parts of the body, apparently telling the body when it is daylight, based on the light coming in through your retina. Your retina is actually a sliver of brain, tucked into the back of each eye. The SCN tells the body to get drowsy or alert, based on the amount of sunlight coming through. This daily pattern is called your circadian rhythm. Under normal conditions, your body will regulate itself pretty well, using sunlight as a cue for the daily cycle of waking, working, getting drowsy and sleeping. Artificial lighting, long work days, over-stimulation from caffeine, working the night shift, jet lag and other factors can all affect circadian rhythms, throwing everything out of balance. Prolonged exposure to these factors interrupts your natural sleep pattern and deprives the brain of valuable repair and memory consolidation time.

Circadian rhythms may actually occur in all living things. A recent study of fruit flies found that these tiny organisms use genes to respond to the daily cycle of light and dark, triggering the build-up and break down of proteins critical to sustain life. In fact, Nobel prize winner Jeffrey Hall says the circadian rhythm is as “fundamental to survival as respiration” and suggests that any organism that has not found a way to develop this skill is probably extinct.

Tips for a Good Night’s Sleep

In today’s world, being busy and getting too little sleep is sometimes used as a means of self-aggrandizement. “Look at how important I am! I’m crazy busy and never get enough sleep.” If the statement is true, the speaker is probably disorganized, making poor choices and not taking proper care of their body and mind. Here are a few tips to get a better night’s sleep:

Set a regular schedule – and follow it

People who vary their bedtime every day have a harder time going to sleep, so try to get up and go to sleep at the same time, even on weekends or when traveling.

Exercise regularly

Exercising for at least 20 or 30 minutes a day nearly every day helps you fall asleep at night, if you don’t exercise too soon before bedtime. Ideally, try to get your exercise in five to six hours before you want to fall asleep.

Avoid caffeine, nicotine, and alcohol

Caffeine and nicotine are stimulants that can interfere with your natural processes for getting drowsy and falling asleep. A “nightcap” may initially make you drowsy, but it robs your brain of REM sleep and keeps your brain in a constant sleep-deprived state, no matter how many hours you sleep.

Have a bedtime ritual

Establish a set of relaxing behaviors you do about 30 minutes before going to bed. Over time, your brain begins to associate falling asleep with these rituals, making it easier to fall asleep.

Wake up with the sun

Your brain is programmed to wake up gradually, as the sun rises. If your work schedule doesn’t make this practical, consider getting a special light to simulate the right wavelengths, programmed to wake you up with simulated sunrise during the winter months.

Get as much natural light as possible throughout the day

If you work in an office, it’s important to get outside frequently for fresh air and sunlight. These natural stimulants help keep you alert throughout the day and keep your brain’s inner clock running smoothly.

Don’t fight insomnia

If you’re lying in bed for more than a few minutes and can’t fall asleep, go ahead and get up for a while. Lying in bed “trying” to fall asleep only raises your stress level and makes it harder.

See your doctor for possible sleep disorders

Sleep apnea and other disorders can be very detrimental to overall health, so be sure to seek medical attention if you suspect you have any of the symptoms in this online quiz.

Sleep is Magical

Some people believe sleep to be a magical experience, where our spirit guides whisper our true names, loved ones, long dead, come back to visit, and we see the future in visions painted by the gods. It turns out they’re right.

Sweet dreams, everyone!