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UCLA study posits a connection between REM sleep and body temperature

Original Article By: Danielle Cho and Lyah Fitzpatrick

Summarized By: Neurobit

A recent study conducted by UCLA researchers suggests that the REM stage of sleep has evolved to help animals maintain a baseline brain temperature that allows them to stay alert. According to the study, REM sleep acts as a sort of biological thermostat, heating up the brain so that animals can stay aware of their surroundings. This theory contrasts with the widely-accepted narrative that REM sleep plays a role in memory consolidation and learning. The study, which was published in October, analyzed data on REM sleep across a wide range of species to reach this conclusion.

The study, led by Jerome Siegel, a professor-in-residence of psychiatry and biobehavioral sciences, reviewed existing data on REM sleep across various species and found a correlation between the length of REM sleep and body temperature. He hypothesizes that a mammal's body temperature determines the length of its REM sleep. The study also suggests that this could have implications for human insomnia, as artificially controlled temperatures in man-made environments may interfere with sleep cycles. According to Siegel, this may be a potential reason for the high rate of insomnia in modern populations. Christopher Colwell, a professor-in-residence of psychiatry and biobehavioral sciences and an expert on circadian rhythms in mammals also supported these conclusions made by Siegel.

Furthermore, Siegel found an almost perfect inverse relationship between REM sleep length and body temperature. He observed that species with lower average body temperatures had higher amounts of REM sleep and this relationship was stronger than any other factors that could be linked to REM sleep length.

Alon Avidan, a professor of neurology and the director of the UCLA Sleep Disorders Center, believes that researching the sleep patterns of animals can provide valuable insights into human sleep. He states that by understanding the evolution of sleep in animals and comparing it to humans, important distinctions can be made about the functions of REM and non-REM sleep.

Despite the study's findings, not all experts in the field agree with the hypothesis that REM sleep acts as a biological thermostat. Colwell finds the argument on the evolutionary basis of REM sleep to be compelling but does not believe that it necessarily disproves the idea that REM sleep plays a role in learning and memory. He believes that the study will encourage other scientists to further investigate the purpose of REM sleep and to strengthen their arguments. Avidan also encourages ongoing research on REM and non-REM sleep, stating that there is still much to be discovered about sleep in general.


Cho, D., & Fitzpatrick, L. (2023, January 13). UCLA study posits connection between REM sleep, body temperature. Daily Bruin. Retrieved January 13, 2023, from

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