Which scenario do you usually experience? Do you get good amount of sound sleep and wake up refreshed and ready to go? Or, do you get to bed late and then end up tossing and turning the entire night? We wouldn’t have to talk so much about sleep quality if we all had a good night’s sleep – every night. So, it looks like it is the aftermath of tossing and turning all night that we need to address.
We all know how it feels to not sleep: everything requires effort; we lack energy and motivation; and we feel groggy, irritable, and snappish. We wear our nerves on the outside of our body. Sleep is not a period of rest, however. Our brain is very busy during sleep and serves an active, essential function. Sleep loss or chronic sleep disruption has many negative consequences, including adverse effects on metabolism and immune function. The most obvious of these adverse effects are on the brain. Cognitive deficits of many kinds are apparent – after just one night of total sleep deprivation or when sleep is cut short by several hours every night for a week or more.
Attention, working memory, and the ability to learn and remember decline. When we are sleep deprived, it is more difficult to speak fluently, assess risks, and appreciate humor. Importantly, experiments have shown that these cognitive impairments can be reversed but not by the same period of ‘quiet wakefulness’. There is evidence that cognitive deficits caused by sleep loss at night can be prevented or delayed by naps.
What distinguishes sleep from quiet, restful wakefulness? Sensory disconnection is the answer.
During quiet restfulness, when we sit on the sofa in a silent dark room after having exercised – our muscles recover from fatigue. Yet, we are still able to react and move promptly if the phone rings – we are still connected to the world. On the other hand, when we are deeply asleep, our capacity to react to mild stimulus – like a noise coming from another room, or that phone call, is substantially reduced. So, we must take into account that when we sleep, we are essentially offline; sensory disconnection must be an essential requirement for whatever function sleep serves.
Now, why do we sleep? We just heard all of the things that can happen when we don’t sleep. What does sleeping actually do for us?
Sleep was originally believed to keep us safe at night, conserve energy, and allow our bodies to rest and repair. But as research really dug into our brain function while we sleep it uncovered a long list of brain functions that occur. If fact, our brain is almost as busy when we sleep as when we are awake.
Let’s take a look:
Clear out toxins. Not all that long ago it was discovered that we have a system that drains waste products from out brain. Cerebrospinal fluid (CSF), a clear liquid surrounding the brain and the spinal cord, moves through the brain along a series of channels that surround blood vessels. This system is managed by the glial cells (another type of brain cell), so the researchers called it the glymphatic system. The glymphatic system’s job is to clear out and recycle all the brains toxins.
The scientists reported that the glymphatic system can help remove a toxic protein called beta-amyloid from brain tissue. Beta-amyloid is renowned for accumulating in the brains of patients with Alzheimer’s disease.
Repairs daily wear and tear. New research indicates that chronic sleep deprivation can lead to irreversible brain damage. Short sleep may also be linked to shrinking brain volume! Scientists have concluded that the deeper stages of sleep are crucial for repairing the body – including the brain.
Makes order from chaos. As you go about your daily activities, your brain is exposed to thousands of stimuli, auditory, visual, and neurosensory. And it can’t possibly process all that information as it comes in. A lot of tagging and archiving of memories goes on at night while you are sleeping. People who think they have adapted well to sleeping just four or five hours a night are often wrong; memory tests show that they are not functioning optimally.
Creates memories. One of the chemicals involved in creating memories, acetylcholine, is involved in sleep and dreaming. What happens in people who start to develop Alzheimer’s is the brain cells that produce acetylcholine are destroyed, so people stop dreaming as much. Interestingly, a side effect of the most used drug to treat Alzheimer’s, Aricept, is its ability to induce vivid dreams.
Let’s investigate the process of making memories in the brain while we sleep. When we sleep – and this includes napping, our brain is very busy. Memory formation and consolidation are crucial parts of brain function while we are sleeping. As we gather information while we are awake it is first contained within short-term memory. As we sleep, this information is moved to the hippocampus, the center of learning and memory. The hippocampus is very busy while we are awake, so when the inputs are quiet, the hippocampus gets busy consolidating memories.
What does this even mean? When the signal of the input is strong enough, the hippocampus scans the brain to determine if there is another memory similar to it. If there is – the memories are consolidated.
What happens then? The consolidated memories are stronger, meaning we can recall them faster and easier. It also changes our memory a slight bit. Because the memory is consolidated, we don’t quite remember it the way it might have actually happened. We experience this phenomenon when we meet up with friends we haven’t seen for a long time. Our stories of old times will be similar but not the same. Our life has added a little twist to our new memories.
Our brains have a lot to do and just can’t get it done if we are sleep deprived. So, the moral of the story is: Get good sleep!