While you sleep, a lot is happening in your body. Did you know that you have around four to five dreams every night? When you wake up in the morning, you can probably only remember very few of them. Neurophysiological dream research has been exploring the question of what actually happens when we dream since the end of the 19th century. Among other methods, measurements of brain activity help scientists trace the processes behind this phenomenon. You can find some of the key findings here.
Sleep phases
By now we know that we go through several phases while we sleep. One sleep cycle lasts around 90 to 110 minutes and then repeats. Our sleep phases are generally divided into REM and non-REM phases. REM stands for Rapid Eye Movement and describes the very fast eye movements we make during sleep, even though our eyes are closed. After several non-REM phases (that is, phases in which we do not move our eyes) a REM sleep phase follows at the end of a sleep cycle, and in this phase many people dream particularly vividly. However, dreaming can also occur during non-REM phases. During REM sleep, the neurotransmitter acetylcholine is released more strongly in the brain. This substance and its receptors appear to play an important role in regulating REM sleep.
Active brain regions
When we dream, many regions of our brain are active. The cortex, for example, is involved in the content of our dreams, meaning it contributes to whether you run away from monsters, meet other people, or fly like a bird in your dream. Emotions in both waking and dreaming states are supported by the limbic system (a network involved in processing emotions). Part of this system is the amygdala, which is often associated with fear and is frequently particularly active during dreaming.
The fact that we experience dreams mainly as images can be explained by the brain’s ability, while we dream, to generate activity patterns similar to those involved in seeing when we are awake. This is because the visual cortex (the part of the cerebral cortex responsible for vision) can be similarly active in both states. Brain regions that in waking life allow us to taste, smell, or feel pain are, by contrast, often less strongly active. The frontal lobe is also often less active during our dream phases than it is when we are awake. In the waking state, among other things, it plays a role in logical thinking and short-term memory. This reduced activity could therefore help explain why we so often stop remembering our dreams shortly after waking up, and why the actions in our dreams are often so unrealistic.
Function and meaning of dreams
But why do we dream? And what functions and meanings can be attributed to our dreams? Unlike the processes in the body and brain, there is still disagreement in research when it comes to these questions. While some researchers see dreams as random, functionless by-products of neuronal information processing, others assume a problem-solving or learning function, or suggest that emotions are processed in dreams. A connection between dreaming and creative processes has also been proposed, as has preparation for real-life situations (especially during REM sleep). Whatever the case may be, restful sleep is essential for our health and supports our waking life in many ways.
Key takeaway
In summary, dreaming is a completely natural part of our sleep: A combination of active brain processes, feelings, and impressions that accompanies us night after night. Even if we often remember only fragments in the morning, our nights do a great deal in the background to support recovery and well-being. That’s why it’s worth giving sleep (and with it, dreaming) conscious space: your body and your mind will thank you for it.
Further information on the topic can be found here:
Muzur, A., Pace-Schott, E. F., & Hobson, J. A. (2002). The prefrontal cortex in sleep. Trends in Cognitive Sciences, 6(11), 475–481. https://doi.org/10.1016/S1364-6613(02)01992-7
Siclari, F., Baird, B., Perogamvros, L., Bernardi, G., LaRocque, J. J., Riedner, B., Boly, M., Postle, B. R., & Tononi, G. (2017). The neural correlates of dreaming. Nature Neuroscience, 20, 872–878. https://doi.org/10.1038/nn.4545