Cloudy Dreams

Written by Panamdeep Thind and Edited by Catherine Zhang

Dreams are a unique kind of mystery— as we sleep, we put together an assortment of images which we either remember or forget once we’ve awakened. Over the years, dreams have been analyzed by many scientists who have formed many theories about them. 

While many neurologists and psychologists have multiple theories on what dreams are and what they signify, the most common theory we know of is Sigmund Freud’s Theory of Dream Fulfillment. Freud’s theory focuses on the idea that the images we dream of are indicative of a person’s deepest desires [1]. However, this theory was contested by two scientists, J. Allan Hobson and Robert McCarley, who claimed that dreams hold no ulterior purpose, but are rather completely random [2]. The duo proved their theory with their Activation Synthesis Theory, which explains that the brain is constantly working, even as we are asleep. 

Deep sleep, or rapid eye movement sleep, commonly known as REM, is a later stage in the sleep cycle when the brain is at its most active state. During REM, the brain shows a high level of activity and dreams can be interpreted as random brain signals [2]. Two particular parts of the anatomical structure of the brain, the temporoparietal junction (TPJ) and the medial prefrontal cortex (MPFC) are highly critical in forming dreams. The TPJ collects information from inside and outside the body and processes it along with the MPFC. During sleep, these brain areas have been proven to show the most activity [3]. In order for a dream to actually occur, a connection must occur between the neurons found in regions of the brain called the hippocampus and the prefrontal cortex [4]. 

The speed and unison of the activity in the neurons in the TPJ and MPFC change in different parts of the sleep cycle. A study on sleeping mice discovered that the connection made between the neurons is well timed during slow wave sleep (SWS or N3), but not during REM sleep. According to the Crick and Mitchison Theory of Reverse Learning, REM sleep is the stage in which most dreams take place, but also where most dreams are forgotten [1]. SWS rejuvenates the body and is characterized by its slow brain waves that allow the body to rest for the next day. Since most dreams are formed during REM sleep, dreams are most often forgotten because the hippocampal and prefrontal cortex neurons spike in an untimely manner during REM sleep [5]. 

Many things take place during the sleep cycle that determine the level of dream recall. Certain devices, such as an electroencephalogram (EEG), can detect patterns of brain activity that reflects the dream state. An increase in desynchronized electrical patterns in the brain during REM and SWS reflect higher dream recall, whereas a lower delta and higher beta power (values used to measure EEG patterns), are indicative of a lower dream recall [6]. In the experiment conducted, these values displayed a pattern connecting them to a lower dream recollection. According to the Initial Dream Theory of Activation Synthesis, many parts of our brains work while we sleep; therefore, dream recall can be difficult. 

Many factors contribute to dream recollection, including many parts of the brain. Above, dream recollection was broken down using a scientific point of view, by describing the activity in multiple parts of the brain. In terms of external wellness, no factor has been proven to strengthen dream collection aside from achieving REM sleep. 

References:

1. Brown, D.W. (2004). Crick and Mitchison’s theory of REM sleep and neural networks. Med Hypotheses, 40:329–331. 
2. Cherry, Kendra. “7 Theories on Why We Dream.” Verywell mind, Dotdash, Jan. 1 2020, www.verywellmind.com/why-do-we-dream-top-dream-theories-2795931.
3. Euston, D.R., Gruber, A.J., McNaughton, B.L. (2012). The role of medial prefrontal cortex in memory and decision making. Neuron, 76:1057–1070.
4. Eichenlaub, J.B., Nicolas, A., Daltrozzo, J., Redouté, J., Costes, N., Ruby, P. (2014). Resting brain activity varies with dream recall frequency between subjects. Neuropsychopharmacology, 39:1594–1602. 
5. California Institute of Technology. “Why Dreams Are So Difficult To Remember: Precise Communication Discovered Across Brain Areas During Sleep.” ScienceDaily, ScienceDaily, 9 March 2009, www.sciencedaily.com/releases/2009/02/090225132249.htm.
6. D’Atri, A., Scarpelli, S., Schiappa, C., Pizza, F., Vandi, S., Ferrara, M., Gennaro, L.D. (2019). Cortical activation during sleep predicts dream experience in narcolepsy. Annals of Clinical and Translational Neurology, 6:445–455.