The Science of Sleep: What Happens when we Sleep?

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The Science of Sleep: What Happens when we Sleep

Sleep accounts for anywhere from 1/4 to 1/3 of our lifespan. That’s anywhere from 25-33%! But have you ever stopped to wonder what happens when you sleep or why is it’s so important?

Until the 1950s, it was believed that sleep was a passive activity during which time the body and brain were predominantly dormant. But as more scientific studies about sleep emerge, it turns out that sleep is anything but passive!

Many activities take place during sleep that are necessary to life. In fact, these activities are closely related to our quality of life.

But what actually happens while you sleep?

Sleep expert and neurologist at Johns Hopkins, Mark Wu, M.D., Ph.D., has been researching what happens during sleep. He, along with other researchers, are spending countless waking hours learning all they can about the processes that take place during sleep and how they affect both our mental and physical health.

Before we get to that, let’s talk science.

Types of Sleep: REM and non-REM

While we sleep, our brain cycles repeatedly through two different types of sleep. They include REM sleep (Rapid-Eye Movement) and non-REM sleep.

Non-REM sleep is the first part of the cycle and happens in four stages.

• Stage 1: Between wakefulness and falling asleep.

• Stage 2: Light sleep. During this time, your breathing and heart rate stabilize and your body temperature lowers.

• Stage 3: Deep sleep.

• Stage 4: Deep sleep.

Stages 3 and 4, deep sleep, are the most restful and restorative times of the sleep cycle. They are also the times when content learned and new memories acquired during the day become embedded in our long-term memory.

REM sleep happens next. During this phase, your eyes move rapidly behind closed eyelids - hence the name “Rapid-Eye Movement.” Your pulse quickens and your body becomes temporarily paralyzed as you dream. Brain wave activity during REM sleep is very similar to the brain wave activity we experience when we are awake.

The cycle repeats itself four or five times throughout the night. But with each cycle, time spent in deep non-REM sleep decreases and time spent in REM sleep increases.

But why is sleep so important?

The importance of sleep

As previously mentioned, many processes happen during sleep. In fact, sleep significantly impacts several brain functions.

Here’s what happens:

1. Memories are imprinted into long term storage.

During sleep, episodic memories acquired during the day are transferred from their short-term location in the hippocampus to the brain’s cortex where they become part of our long-term memory. If we don’t get enough sleep, we can’t process what we’ve learned during the day. Moreover, we have more trouble remembering it in the future.

More food for thought: Students who pull an all-nighter in an attempt to remember important information before an exam may be better off getting some quality zzz’s instead!

2. Brain plasticity is increased.

Sleep provides time for nerve cells to communicate with each other and is vital for “brain plasticity.” This is our brain’s ability to adapt, absorb new information, and change.

3. Toxins are purged.

Sleep promotes the removal of waste products and toxins from brain cells. Recent studies suggest that this housekeeping or clean-up process may be more important than we realize, as sleep affects every part of our body including our brain, heart, and lungs. It also has an impact on our memory, mood, and metabolism.

4. Immune function is strengthened.

Finally, while we sleep our immune function is strengthened so we have a better chance of resisting disease and fighting off illness. The mechanism behind this is closely tied to the last point about sleep’s amazing “housecleaning” ability.

Sometimes there’s nothing quite as good as a restorative, quality sleep to boost the immune system, allow your body to purge toxins and excess cortisol, and help you feel rejuvenated.

Yes, quality sleep really is vital to the entire body.

Unfortunately, many of us don’t get a good sleep on a regular basis. Research indicates that a chronic lack of sleep, or getting poor quality sleep increases our risk for developing hypertension, cardiovascular disease, depression, diabetes, and even obesity.

Indeed, when we don’t get enough sleep, our health risks rise. We are more susceptible to experiencing depressed episodes, seizures, and high blood pressure. Migraines can worsen. Immunity is compromised, and the likelihood that we’ll experience illness or infection increases.

Did you know that missing even one night of sleep can create a pre-diabetic state in an otherwise healthy person?

How sleep affects learning and memory

The connections between sleep, learning, and memory are quite complex and not entirely understood. Yet studies on both animal and human subjects suggest that both the quality and quantity of sleep we get have a significant impact on both learning and memory.

Sleep affects these important processes in two primary ways.

First, someone who is sleep-deprived cannot focus their attention well. As a result, they cannot learn efficiently.

Second, since memories are consolidated as we sleep, quality sleep is essential so that we can remember new information learned and be able to recall it later. 

Even though the exact mechanisms are unknown, memory and learning are often described in terms of these three functions: acquisition, consolidation, and recall.

Acquisition happens when new information is introduced into the brain. Consolidation is the process through which memories become ingrained. And recall refers to our ability to access information (consciously or unconsciously) after it has been stored.

All three of these steps are required for our memory to function properly. Memory consolidation happens while we sleep as neural connections that form our memories are strengthened.

Though researchers cannot fully agree as to how sleep makes memory consolidation possible, many believe that the characteristics of certain brainwaves throughout the different stages of sleep may be associated with the formation of specific types of memory.

Now that you know just how important it is to get enough quality sleep, why are many of us not making sleep more of a priority? 

Maybe you’re one of the many people who struggle to fall asleep at night. Or perhaps you wake in a fog after tossing and turning all night. 

If so, be sure to tune in next week as we explore how to get a better sleep, and how modern life may be part of the problem. 

As always, I welcome your thoughts and value your feedback. Let me know what you think by dropping me a line or commenting below.

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