Your consciousness has been altered, replaced with a series of cryptic, sometimes harrowing hallucinations, all five of your senses are been hindered and the action of moving once-voluntary muscles has become utterly impossible…
It sounds like a scene out of a dystopian sci-fi movie but in fact, humans on average spend around 26 years of our life in this state (and most people would prefer more of it). Yes, I am talking about having a catnap, a snooze, getting some shut-eye, a siesta. I’m talking about wondrous sleep.
Sleep is an essential component of the lifestyles of mammals, reptiles and birds. Fish and insects also have mechanisms of sleep. Sharks, for example, are believed to have periods of awake and rest whilst still pumping water over their gills to breath. They do not however, fall into the “deep sleep” we are familiar with. Sleep is required as it allows our minds and bodies the opportunity to rest and repair. It may seem obvious but a person cannot survive long without sleep. For an avid nap-taker like myself it seems shocking but the world record for staying awake is believed to be around 11 days!
Falling asleep and getting a good night’s rest is not as simple as pulling up the blankets at night and waking up bright-eyed the next morning (or vice-versa for shift-workers!). Sleep is made up of a number of cyclical stages characterized by the active brain waves.
The first stage, the hardest for many, is actually falling asleep. Throughout the evening, levels of the chemical melatonin increase as the body prepares for sleep. Lately there has been a lot of discussion about the use of smartphones etc. in bed. The “blue light” from screens tricks our brains into thinking it is still day time hindering the release of melatonin, ergo thwarting our bodies’ preparation for sleep. There is actually an app available that counteracts the “blue light” on your smartphone, but it is usually recommended to stay away from screens two or more (if you can manage) hours before going to bed.
The first stage (falling asleep) is characterized by alpha and theta brain waves. The brain is slowly beginning to wind down after a long day and it is during this time we can experience “hypnagogic hallucinations,” also known as “almost jumping out of bed because you just had an incredibly vivid dream of falling off a cliff” (term may not be scientific).
The next stage is Non-Rapid Eye Movement (NREM). This is characterized by short rapid brain waves known as “sleep spindles”. These then progress into slower, deeper delta waves, in this stage we still have the ability to move around in order to thermo-regulate (e.g. curling up for warmth, throwing your leg out to cool, etc.). This sleep stage is when our body lowers in temperature, our breathing slows and when phenomenon such as sleepwalking is most likely to occur.
Rapid Eye Movement (REM) Sleep is characterized, as the name suggests, by rapid eye activity, increased breathing and brain activity. Although the brain is more alert, voluntary muscles are usually paralyzed. REM sleep is important because it is when dreaming occurs. It is hard to quantify but it is believed that on average, adults dream around 3-5 dreams per night. No one is certain but it is theorized that we dream in order to consolidate our memories and process new information gained from our day. Although dreams may seem like long, adventurous epics spanning hours, it is believed that most dreams only last about 5 minutes.
Throughout the night, we experience cycles of NREM and REM and if you are a bit of a sleep enthusiast like me, there is a free app for tracking the types of sleep you are experiencing each night.
The presence of sunlight and internal circadian rhythms stimulate the body to begin waking up (note: the above title I am not going to apologize for) and thus begins the final stage of sleep: waking up. This occurs when signals tell the brain to begin drifting out of REM sleep and back into the real world. You will also begin to wake up if your homeostatic need for sleep has been sufficiently reduced. Some people can naturally wake at the same time everyday and others struggle with that stupid alarm going off right in the middle of a really great dream!
Even as such a vital part of our existence, there is still so much unknown about sleep. Further studies are sure to enlighten us more on the pastime. To quote William Shakespeare, “We are such stuff as dreams are made on; and our little life is rounded with a sleep.”
Good night and sweet dreams!
First published on 9th July 2015 on RiAus – Australia’s Science Channel