On the hottest summer days, you may find yourself dozing off in the middle of the day. In some parts of the world, it’s a cultural norm to schedule “siestas” and shutter businesses during the warmest hours of the day. As it turns out, biology, not just culture, may be behind this.
In a new study, published Aug. 17 in the journal Current Biology, researchers found that fruit flies are pre-programmed to take a nap in the middle of the day. A follow-up to their 2020 Biology paper that identified a brain thermometer only active in cold weather, the new paper explores a similar “thermometer” circuit for hot temperatures.
“Changes in temperature have a strong effect on behavior in both humans and animals, and offer animals a cue that is time to adapt to the changing seasons,” said Marco Gallio, associate professor of neurobiology in the Weinberg College of Arts and Sciences.
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Just as they expected based on the results of their previous paper on cold temperature, researchers found that brain neurons receiving information about heat are part of the broader system that regulates sleep. When the hot circuit, which runs parallel to the cold circuit, is active, the target cells that promote midday sleep stay on longer. This results in an increase in midday sleep that keeps flies away from the hottest part of the day.
