Have you ever wondered what happens while you sleep at night beyond restoring your energy levels? The brain remains active during the night, and current hypotheses believe that this is because the brain is hard at work balancing its connections so that when morning arrives, you’re ready for another day of learning.
When we take a closer look at why this homeostasis is completed, we can better understand just why sleep is so important for our learning capabilities.
Why Do We Sleep?
It’s a universal need amongst humans and animals, but why is sleep necessary? Scientists have been able to determine the harm that can come from sleep deprivation, including poor focus and depleted immune systems, but what is it about sleep that serves such a vital role in our well-being?
As it stands, experts are still not entirely sure how sleep produces all of its benefits, but each day, they’re getting a little bit closer to understanding what exactly is restored during sleep.
What we do know is that chronic sleep deprivation can increase the risk of health problems such as cardiovascular disease, high blood pressure, depression, diabetes, and obesity. We also know that sleep is important for many brain functions, including supporting the communication of neurons in the brain and removing toxins in the brain that build up during our waking hours.
Researchers even have hypotheses on what happens in our brains during sleep in order to balance the learning that we do during the day.
The Synaptic Homeostasis Hypothesis
There is still a lot about sleep and the role of the brain during the night that remains unknown, which is why scientists often work in terms of hypotheses. One such hypothesis is that sleep is needed in order for the brain to undergo plasticity because of the immense energy requirements of this action.
When you learn, your brain undergoes synaptic strengthening, increasing the size and strength of connections between related areas of the brain and allowing you to recall information quicker. However, this is an energy-hungry process that increases the energy consumption in the brain and can overload the capacity for processing information.
When we sleep, it’s believed that certain synapses—those that are no longer important—are weakened or destroyed in order to make room for increases that occur during learning. This way, the irrelevant material that can otherwise interfere with learning is removed.
It’s been shown that even short periods of sleep or wakefulness alter your synaptic activity at multiple levels and can make synapses shrink (when sleeping) or grow (when awake and learning).
In one study, researchers examined synaptic connections in mice while sleeping and after being awake in order to see these changes. They found that the synapses of the mice decreased when the mice had slept, which equates to a decline in the number of synaptic connections. Furthermore, rather than being a uniform decline, the downscaling centered on small spines, sparing the larger ones that the researchers suspect were involved in learning.
Another study further proved this hypothesis, finding that sleep is associated with a decline in the size of dendritic spines, which are small protrusions on a nerve cell that receive information and then transfer it to the neuron’s cell body—this shows that during sleep irrelevant sections of the spines are removed, decreasing their size.
As for how this downscaling occurs, researchers have gained some insight. Specifically, they have discovered that the number of AMPA receptors is reduced during sleep.
AMPA receptors are found in brain cells and allow for information to be shared from cell to cell, making them a critical component of our brain’s function. The researchers found that AMPA receptors are removed from shrunken spines thanks to a protein called Homer1a, which is active while we’re sleeping. When AMPA receptors are removed, the synapses shrink and weaken, which is how irrelevant information is “forgotten” during sleep, making room for more learning the next day.
Ultimately, the synaptic homeostasis hypothesis offers insight into why the phrase “sleep on it” holds so much merit; while sleeping, your brain removes irrelevant connections, allowing the important ones to shine through so you can think more clearly. Furthermore, this hypothesis shows that sleep restores the energy, supplies, and extracellular space that are used up during the day, restoring cognition, vigilance, and learning. In this way, sleep balances out what occurs during the day, allowing the cycle to repeat as more information is learned.
The Role of Slow-Wave Sleep
Some researchers hypothesize that synaptic downscaling occurs during slow-wave sleep, in particular. Also known as deep sleep, this third stage in the sleep cycle is associated with slow-wave brain activity, hence the name.
The hypothesis is that synaptic potentiation is tied to the regulation of slow-wave activity, which is why slow-wave activity is then associated with synaptic downscaling.
This hypothesis may offer insight into why deep sleep is so beneficial—during this time, your brain is removing unnecessary connections to make room for more learning the next day.
Sleep Tips to Let Your Brain Balance
If the synaptic hypothesis is right, the time that you spend asleep is crucial for balancing your brain connections and setting yourself up for success the next day—only by removing irrelevant connections can you make room for new and stronger connections.
Try out these tips to get a good night of sleep with plenty of deep sleep:
- Keep it regular. A schedule is key for your sleep, so be sure to go to bed at the same time each night and wake up at the same time each morning.
- Avoid caffeine before bed. Caffeine works against sleepiness and can make it hard to fall asleep.
- Set the stage. Ensure your bedroom is dark, cool, and quiet so that you don’t have any distractions waking you up.
- Relax. It can be hard to sleep when you’re stressed, so try some relaxing activities such as reading or taking a warm bath before going to bed.
Sleep is a crucial time for balancing brain connections and removing irrelevant connections. If you struggle to fall and stay asleep, consider reaching out to a doctor for guidance—your brain will thank you.