Your Sleep Cycle Is More Complex Than You Think. Here’s Why

June 3, 2020

By Lida Tunesi

Our circadian rhythms involve more than just when we go to sleep and when we wake up. They also involve environmental cues like light and temperature.

flat color illustrated sleep cycle concept art

Our circadian systems help our bodies and minds stay in tune with the time of day, and scientists are increasingly finding out how important this is. Certain environments can lead to weakened circadian rhythms, potentially leading to problems with sleep and metabolism, and increased cancer risk. But researchers are still working out some of the finer details of the system.

In a new study in Current Biology, scientists found that a group of neurons in the fruit fly’s circadian network play a very different role than previously thought. Humans have similar neurons, so the results could help us understand our own biological timekeeping.

Hannah Pettibone and Joseph Bogart, research assistants at the Advanced Science Research Center at The Graduate Center, CUNY, and Professors Boyan Kostadinov (City Tech) and Orie Shafer (CUNY ASRC) were authors on the paper along with Maria de la Paz Fernandez of Barnard College.

There are two parts to the circadian system, Shafer told CUNY ASRC. One is built in, a sort of biological clock in our brains. The other takes in environmental cues like light and temperature to align the internal clock with that of Earth’s 24-hour day.

Fruit flies, which act as simple models for biologists studying complicated systems, have brain cells called small ventrolateral neurons. These neurons restructure themselves daily, growing more branched early in the day then de-branching themselves in the evening. Scientists long thought this remodeling was part of the fly’s internal clock.

But when the new study authors prevented these neurons from developing, the flies’ internal timekeeping continued unaffected. What did change was the flies’ abilities to mentally encode temperature cues from their environment. This supports the idea that the neurons’ restructuring is actually involved in the alignment, or entrainment, part of the circadian system. Humans have similar neurons that remodel themselves daily, so the researchers think that ours likely play the same role as the flies’.

In light of this, the researchers now hypothesize that the daily branching and de-branching helps change the neurons’ sensitivity to temperature throughout the day. Shafer and colleagues hope to test this once they are able to return to the lab.