An early morning jog may help your jet lag. Physical activity can warm up the brain's biological clock, helping it adjust to a new time zone. While seeing the morning dawn remains the best way to adapt to a new time zone, further research into brain temperature may bring new ways to recover from a long flight.

Our biological clock, which drives our daily circadian rhythms, sits above the roof of our mouth in a section of the brain called the hypothalamus. Our mental watch is normally 'set' to the correct time by the suprachiasmatic nucleus (SCN) responding to signals given from the optic nerve. Simply put, if you see the dawn, your biological clock sets itself to morning.

Now Erik Herzog, an assistant professor of biology at Washington University in St. Louis, Missouri, has identified a heat sensing component to this mechanism. Our brain temperature fluctuates, heating up during the day, cooling at night. If you adjust this cycle—by heating up the brain earlier or later—the SCN adjusts accordingly.

"It's sort of like resetting your watch when you fly to Paris," says Herzog. "We could reset the biological clock by exposing it to a temperature cycle." Brain temperature can be changed with physical activity, fever, aspirin or melatonin.

Herzog, working with mice SCN cells grown in vitro at his lab, found that he could completely reverse circadian rhythms by adjusting the temperature of the cells. The results are published in the Journal of Neurophysiology.

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