Elahniverse Dictionary
Zeitgeber
A time cue that sets the body's clocks. Light for the brain's clock, temperature and meals for the rest.
A zeitgeber, German for "time-giver," is any external cue that sets the body's internal clocks. The word comes from Jürgen Aschoff, who in the 1960s sealed volunteers in a bunker with no daylight and watched their rhythms drift, proving the clock is endogenous but needs cues to stay aligned with the world.
Light is the master zeitgeber for the brain's central clock. But it is not the only one, and this is the part most people miss. The clocks in your organs and tissues take their cue from temperature and meal timing far more than from light. A change in core temperature can reset them directly.
That is why heat and cold are more than sensations. A well-timed swing in body temperature is a signal your peripheral clocks are built to read, which is how a practice about warmth and cold ends up being a practice about sleep and daily rhythm.
Mentioned in
Further reading
- Aschoff, Circadian Rhythms in Man, Science 1965 — the Andechs bunker studies, where Aschoff coined the term zeitgeber
- Buhr, Yoo, and Takahashi, Temperature as a Universal Resetting Cue for Mammalian Circadian Oscillators, Science 330:379–385 (2010)