What happend in our brain while we are dreaming?

What happend in our brain while we are dreaming?

The fifth stage of sleep consists of REM sleep, which was discovered by physiologists Eugene Aserinsky and Nathaniel Kleitman in 1952. When a person undergoes REM sleep, many of their muscles are paralysed and their eyes move rapidly under their closed eyelids, their heart rate, and breathing rate increase, their blood pressure rises, and their brain activity increases to the same level as when they are awake, producing alpha waves.

Dreams mostly occur during periods of REM sleep, but have also been found to occur at any stage. As we repeat the five stages of sleep, we experience longer periods of REM sleep and shorter periods of deep sleep.

No one knows why we experience REM sleep. One possibility is that it is important for brain development, providing the neural stimulation needed to develop the nervous system. This is known as the ontogenetic hypothesis. Evidence for this comes from the fact that experience less REM sleep as we get older, if it were true then it would mean that REM sleep has no function in adults.

Why do we dream?

While it is still not known why we dream, there are a number of theories. In 1983, biologists Francis Crick and Graeme Mitchison proposed the reverse learning theory, which states that dreams are needed for the brain to remove unnecessary information that it has received during the day.

There is also evidence of the opposite idea, that the brain needs dreams to remember information. This is known as the continual-activation theory.

Another idea is that dreams have the purpose of providing us with simulations, which we can learn from. This is known as the threat simulation theory. Others argue that dreams provide more general simulations, which can also help with problem solving, and emotional control.

Finally, dreams may not have an intrinsic purpose at all and may occur as the by-product of something else that is happening to our brains when we sleep.

What is the meaning of dreams?

Some scientists believe dreams are the cortex's attempt to find meaning in the random signals that it receives during REM sleep. The cortex is the part of the brain that interprets and organizes information from the environment during consciousness. It may be that, given random signals from the pons during REM sleep, the cortex tries to interpret these signals as well, creating a "story" out of fragmented brain activity.

Many cultures attribute prophetic significance to dreams (an example of this can be found in the story of Joseph in the book of Genesis). Others are more skeptical. Aristotle wrote a treatise on dreams 2400 years ago in which he stated that "most so-called prophetic dreams should be classified as coincidences" ("On Prophesying by Dreams". Aristotle, translated by J. I. Beare, http://classics.mit.edu/Aristotle/prophesying.html (link is external)).

...