The bunker experiments that revealed the mysteries of human circadian rhythms

This week I was in Seewiesen, Germany, for the 3rd “Wild Clocks” meeting, a coming-together of ecologists and chronobiologists (that’s clock biologists) from across the globe. The idea behind these meetings is to marry the two research areas so that we can gain an understanding of how biological clocks function in the natural world. The meeting was fantastic, with many talks that will inspire future blog posts here, but the highlight for me was getting the opportunity to visit the famous (in the field of chronobiology, anyway) Andechs bunker site.

The Andechs bunker was a purpose-built underground facility, used from 1964-1989 to study human circadian rhythms. Volunteers went in, some for several weeks at a time, and were completely cut off from any cues from the outside world. Anything that would enable the participants to tell the time was removed – so no outside light, noise, televisions or watches. This setup allowed scientists at the Max Planck Institute for Behavioural Physiology (now the Max Planck Institute for Ornithology in Seewiesen) to study the natural, internal daily rhythms of humans, such as the rhythms of body temperature and sleep and wake. These ground-breaking experiments were led by chronobiologist Rütger Wever, and the director of the MPI at the time, Jürgen Aschoff.

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Left: Rütger Wever analysing data from a bunker test subject. Right: A control panel inside the bunker.

Despite living in a timeless environment, the test subjects seemed very happy. The door to the bunker was never locked and the participants were free to leave at any time. If a participant did open the door, it simply meant the experiment would be finished. It is clear that the test subjects genuinely enjoyed participating, for over the course of the 20+ years that the bunker was in use, around 400 people went in, and only 4 left the experiment early.

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A participant leaves the bunker, seeing the sun for the first time in weeks!

Some participants were very resourceful – for instance, using a record player to time their perfect cooking of a boiled egg (one record played = 3 minutes), or using their time spent in isolation to cram reading material for upcoming exams. Many test subjects started to create paintings – despite claiming they were not artistically inclined before entering the bunker. Others were artists eager to try living completely in the dark to “learn to see with their hands”.

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The inside of the bunker was simplistic – participants had a small kitchen where they could prepare meals, as well as a living area and bathroom

Thanks to all of the volunteers and the scientific efforts of Aschoff & Wever, we now know a huge amount about human rhythms under different conditions. Aschoff had coined the term “Zeitgeber” (time-giver) to refer to the outside cues (e.g. sunlight), that are required in order to synchronise our internal clocks to the right time of day. The Andechs bunker experiments provided the first evidence that human sleep and waking behavior are indeed governed by internal clocks in the absence of zeitgebers. Many other discoveries were made, including sex-difference in rhythms – women participants slept on average ~90min more than men.

The Andechs bunker experiments laid the foundations for chronobiology research in humans and in other animals (some of the later bunker experiments involved birds). Sadly, the land on which the bunker is situated has now been sold for development. The future fate of the bunker is unknown, and its importance in scientific history seems to have been forgotten. That being so, I am very grateful to have had the opportunity to visit the site and venture inside. The bunker has been stripped down and emptied of all of its contents, its two apartments now dark ghostly chambers. Still, I managed to take with me perhaps one of the last remnants of the lives of the volunteers who helped to shape the field of chronobiology today.

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My souvenir from the Andechs bunker 

 

Special thanks to Barbara Helm for providing the Andechs bunker tour and some of the anecdotes here.

Sources:

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