Nature of sleep
The true nature of sleep has not been completely understood yet, and probably will remain a mystery forever.
Nonetheless, there have been many interesting discoveries and scientific findings on sleep.
Here, we try to explain a few interesting facts about sleep without going
into too much detail.
Generally speaking, sleep is a state which is in contrast with wakefulness. When you are awake, you
can respond more efficiently to external stimuli. When trying to define being asleep, one thing that comes
handy is the lack of goal-directed behaviour (in contrast
to when we are awake). Being asleep is generally thought of as a state in which the skeletal muscles relax.
However, phenomena such as sleepwalking bring some interesting points to the table. Scientists
found that during sleepwalking, a portion of the brain is completely
awake. This is why most sleepwalkers can perform certain tasks and routines that you are not usually capable of when
you are fully asleep.
Sleep in animals
In order to find out if other animals sleep in the same way as human beings, scientists use
electroencephalogram (EEG) which records brain activities in terms of electrical signals. It has
been shown that all human beings have more or less the same EEG pattern while sleeping. Furthermore,
this pattern can be used to differentiate if a person is sleeping or not. Similarly, most
mammals and birds show more or less the same EEG pattern while sleeping. However, lizards, snakes,
reptiles, fishes and insects do no show the same pattern. This makes it more difficult to
scientifically differentiate their "sleep" vs awake time. This suggests that the sleep state in some animals
might be closer to wakefulness.
Amount of sleep
Adults typically sleep anywhere between six to nine hours per night. However, over the last few decades, in modern
societies, the number of people who get less than
six hours of sleep has increased drastically. On a separate note, age has a high correlation with the amount of sleep
one should get. For example, on average, an infant spends 16 hours a day sleeping. As he/she ages, this number starts
Our dreams are clearly influenced by what we do during the day. Our brain is complex
enough to divide the night into two phases and process our
memories in different ways during these phases. One of these phases is called slow wave sleep
(SWS) and the other one is called rapid eye movement (REM). We generally dream during both these
phases; but, the nature of our dreams is not the same.
Dreams and our sleep
We saved the best for last. Our dreams are very interesting in nature. Most things we learn
during the day are stored in a structure called hippocampus. While we are in SWS, hippocampus
starts showing movies to our frontal cortex with a very high speed. In general, these are emotionally
charged dreams that are tied to our old memories. Scary nightmares, such as getting buried
alive or a beast sitting on your chest, generally happen during this phase. After this,
our hippocampus shuts down and we transition to REM. This allows our frontal cortex to process the
information. In contrast to SWS, the processing of this information does not happen in a faster
or slower pace and that is why REM feels more real. During this phase, our cortex is trying to
filter the useless memories out.
One interesting fact about our dreams is that the objects and people are familiar. In our dreams, we typically do
not see people that we absolutely do not know. Events that are happening in our
lives are the building blocks of our dreams. However, our creativity can play an important role
in mixing them up. Moreover, there are studies that suggest our dreams evolve along
with our other cognitive developmental processes as we grow up. This one might come as a
surprise to you. There have been studies that looked at the quality of sleep in
couples. For women, sharing a bed with a partner shown to have a negative impact on
the quality of their sleep. However, if there was a sexual contact prior to sleep, this mitigated
the negative subjective results without changing the objective ones (balance of SWS
and REM was still abnormal though). Nonetheless, for men, the quality of sleep was not affected by the
presence of a partner.