Sleep! We spend a third of our lives doing it, and we literally can’t live without it.
It’s a complex phenomenon, and it still isn’t well understood. After more than a hundred years of research, we still don’t know why we sleep. But over the years, scientists have made plenty of fascinating discoveries, like that sleep is vital for memory and that not sleeping can worsen pain and make it harder to heal.
So here are six discoveries that changed the way biologists think about sleep.
1) Not Sleeping Will Kill You
Humans willingly delay sleep all the time. We stay up late for parties and pull all-nighters just to study for tests, but going without sleep for too long will kill you, and we know this partially because of one particular Italian family.
In the 1800s, a Venetian man named Giacomo fell mysteriously ill. He suffered from dementia and an inability to sleep, and when he died. He passed on his condition to his descendants, and the disease still runs in the family today.
When scientists finally identified the cause of the 1970s, they uncovered a sporadic incurable genetic disorder that they called fatal familial insomnia. Its main symptom is progressive insomnia, which causes hallucinations, and delirium and is ultimately fatal.
Even though it is rare, we know which genetic mutation causes the disease. Researchers think this mutation causes damage to a brain region called the thalamus, which is known to regulate sleep and consciousness. The progressive inability to sleep leads to death because the body can never rest. With metabolism in high gear all the time, organs start to fail. Patients may die from more than just sleep deprivation.
2) Sleep Solidifies Memory
We also know that it helps you consolidate memories. But biologists didn’t realize that sleep was critical for helping store memories until about a hundred years ago.
In the 1920s, a group of researchers taught subjects a list of nonsense words. People who got a good night’s rest were better at remembering the list than people who didn’t get to sleep between learning the list and taking the test. This research sparked a wave of studies that found a strong connection between certain kinds of memories: sleeping.
There are different kinds of memory which rely on other brain circuits.
Declarative memories are memories of events and facts, and they rely on an area of the brain known as the hippocampus. They’re separate from non-declarative memory, the kind of memory that builds habits and motor skills like playing the piano. And it turns out sleep is essential for helping the brain retain declarative memory. So the teachers who tell you to sleep the night before the test are right; it’s vital to remember facts and figures.
Other studies have discovered that the type of sleep necessary for this process is non-REM sleep, which is non-rapid eye movement sleep. Even though you might relive your classes in your dreams, when you’re not dreaming, your brain is complex at work solidifying those memories.
3)Active Brain During Sleep
Your brain is super active when you’re sleeping, which might seem like old news. Still, biologists didn’t know that until the 1920’s either when they stuck electrodes on people’s scalps to non-invasively record brain activity. Since it feels like your mind is shutting down when you’re sleeping, scientists have figured that the brain basically goes silent. But once they started actually monitoring brain activity, they learned that that is not what’s happening at all.
They used a new technique called the EEG, which records the electrical signals that come from neuron activity in the brain.
When they recorded people’s brains while they slept, they discovered that instead of silence, the sleeping brain is dominated by big, slow waves of activity. More research has picked apart how different stages of sleep are associated with different wave patterns. And helped clarify the difference between REM sleep and non-REM sleep. The idea that the brain is active during sleep, and the different sleep states correspond to different kinds of wave patterns, changed the way biologists thought about sleep, and helped drive lots of future sleep research.
4) Sleep and Wake Signals
Around the same time as scientists discovered sleep waves, a doctor named Constantin von Economo was treating patients stricken with encephalitis lethargica. Symptoms of the disease include brain inflammation, lethargy and, in extreme cases, an irreversible coma-like state.
Von Ecomono connected the dots between the location of the brain inflammation and the sleep problems seen with the disease. He realized that particular brain regions might be involved in sleeping and waking. He correctly proposed that the brain stem is the centre of the arousal system and sends the waking signal to the forebrain. He also guessed that the hypothalamus is a vital sleep centre that helps regulate the transition between awake and asleep.
Knowing how the brain switches between sleeping and waking is essential for many research areas, like treating narcolepsy and other sleep disorders. And von Economo’s careful study of this disorder and his hypothesis about how the brain might control sleep laid the groundwork for future scientists to better examine the circuits and signals that regulate sleep.
5) Pain and Sleep Deprivation
But doctors have known for a while that insomnia and chronic pain go hand in hand. Obviously, being in constant pain would make it pretty hard to sleep, right? But it turns out that sleep deprivation actually increases pain sensitivity. So if you stub your toe while sleeplessly pacing the room in the middle of the night, it’s gonna hurt more than usual.
In the 1970s, a group of researchers discovered that if you kept rats from getting any REM sleep. They were more sensitive to painful shocks than rats who were allowed to sleep usually.
Around the same time, another group of scientists found that sleep-deprived patients developed muscle soreness. And a study in the mid-2000s found that patients who self-reported insomnia symptoms were more sensitive to pain. So patients with chronic pain might have it even worse if they struggle with insomnia.
There’s evidence that sleep and pain systems use some of the same brain circuitry, so if something goes wrong with one method, it could be going wrong with the other. The discovery of this connection was important for understanding and treating chronic pain conditions, like fibromyalgia, which can be debilitating and significantly impact the quality of life.
6) Sleep Deprivation and Healing
Being sick is exhausting, but why is that? Well, it turns out that sleep isn’t just necessary for our survival; it’s essential for proper healing, too.
In the late 1990s, researchers found that when rats were sleep deprived, their immune systems were hyper-activated, producing lots of inflammatory molecules in their blood. An overactive immune system can lead to problems like chronic inflammation and auto-immune disorders, where a person’s immune system begins to attack its own body.
More recently, in the early 2000s, scientists found that in rats, sleep deprivation makes it harder for burn wounds to heal. All this evidence has led scientists to believe that our immune systems need sleep to function properly and fight illness.
So, you should get plenty of rest if you’re trying to kick that cold.
All these discoveries have significantly affected how scientists understand and study sleep. We know that not sleeping at all can be deadly and that sleep deprivation can lead to health problems.
But there’s still a lot left to learn, and maybe with future studies about sleep, scientists will finally put together all of the pieces of the puzzle and understand completely why we do it.
This article’s entire text and content were taken from SciShow.
