Sleep. It is something we all need (some more than others) and we’ve all woken up remembering a strange dream from the night before. After having a series of bizarre dreams myself, I wanted to know more about why we dream in the first place. What’s the science of dreaming?
Sleeping is as essential as food and water to our health, and getting enough of it is vital. Sleep is important for numerous brain functions, including communication between nerve cells in the brain (i.e. neurons) and may even help to remove toxins which build up in our brains while we’re awake. Despite this, the biological need for sleep is still largely unknown even though various conditions occur when you are deprived of it or have poor quality of sleep (e.g. high blood pressure, diabetes, depression, obesity etc.). In total, six areas of the brain are affected during sleep: the hypothalamus, brain stem, thalamus, pineal gland, basal forebrain, and amygdala.
Our sleep has 5 stages, organised into 2 main stages: non-REM and REM (i.e. rapid eye movement). In a typical night, you will cycle through these stages numerous times, with longer periods of REM occurring towards the morning. Stage 3 of the non-REM is our deepest sleep; we need it to feel refreshed, slowing our heart rate and breathing, and relaxing our muscles. REM however, is a lighter form of sleep when our brain wave activity increases closer to that observed when we are awake. Our breathing, heart rate and blood pressure increase during this period too. REM is the period when most of our dreaming occurs, and as we age we spend less time in REM and therefore, less time dreaming.
There are thousands of websites which claim that they can tell you what your strange dream about dog walking in space meant, but why do we dream in the first place and is there any meaning behind them? We spend ~2 hours a night dreaming and most dreams last around 3 mins (that’s a lot of dreams every night). Although most dreams occur during REM, we do dream throughout the night. Despite the 2 hours we spend frolicking in our imagination, we are unlikely to remember many of the dreams we have had. We cannot be sure exactly why we dream, but it is thought that dreaming may aid us in processing our emotions and events from the day as they invade our subconscious. For example, when I am under more pressure or am stressed, my dreams can become vivid and frightening, like a warning that I’m under too much pressure.
Our ability to recall our dreams varies between individuals, but a study showed those with low frequency theta waves observed in their frontal lobes, were more likely to recall their dreams. Increased activity in this area of our brain is linked to how well we can recall things that have happened to us (i.e. episodic memories). So those of us who have heightened activity in the frontal lobe and can recall our dreams, are more likely to remember our episodic memories from the day too.
Even though it is not 100% known why we dream, there are a few hypothesise: (1) dreams are a way for our brain to organise all the things it has encountered that day. From an advert you noticed on a bus, to the important event you’re organising, it is possible dreams are part of our brain processing long-term memories. Studies have shown that people who are learning have more dreams than those who are not. (2) Dreams may reflect our emotional state. Our brains focus hard all day to make sure we perform small and big tasks, but at night it can slow down as there is less to focus on. During our dream cycles, emotions we have incurred during the day may pop up, causing us to have stressful, joyful, sad, shocking (etc.) dreams. (3) It is also possible however, that dreams are completely pointless, serving absolutely no purpose and are just a byproduct of our brain firing whilst we sleep.
Sleep is fundamental to us being able to function in our day to day lives. Without sleep we can become susceptible to disease and obviously very grumpy, amongst other things. Some people believe that with training we can control our dreams, while some believe that they are completely meaningless. Whatever your opinion, whilst our brains remain a relative mystery, we are unlikely to understand the purpose of having dreams. Maybe science will have the answer one day and I’ll finally understand why I used to dream about being chased into a toilet by a terrifying jester. Happy dreaming.