Chuck Bednar for redOrbit.com – @BednarChuck
By studying the brains of fruit flies in the laboratory, researchers at the University of California-Irvine have discovered the biological mechanics responsible for jet lag, the sleep disorder which affects travelers as they cross time zones on their journeys.
Using a disembodied “brain in a jar” that sounds like something out of a science fiction novel, UC Irvine School of Medicine professor of physiology and biophysics Todd C. Holmes and his colleagues managed to capture the activity of individual circadian clocks at single-cell resolution in order to observe how said internal clock is effectively reset by light.
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They used imaging technology to capture video of fruit fly brains that had been kept alive for six days in a petri dish, and exposed them to an extremely sensitive low-light camera to study for the first time how specific neurons in circadian neural networks react to light cues.
By doing so, they were able to simulate the conditions of rapid travel across time zones, such as would be experienced by someone flying from New York to Los Angeles. Holmes and his fellow authors, who have published their findings online in the journal Current Biology, found that the desynchronization of circadian neurons plays a key role in light-induced jet lag.
It’s all about synergy, guys
Typically, most organisms make daily adjustments to the metabolism and their activity levels in order to synchronize with daylight and other environmental signals that govern their circadian rhythms. Jet lag disrupts this process, they explain, and treatments that accelerate the process of desynchronization before travel could be used to speed up post-travel recovery.
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“Remarkably, our work indicates that the way you feel while jet-lagged exactly reflects what your nervous system is experiencing: a profound loss of synchrony,” Holmes said in a statement, adding that one single light pulse cued the biological clock of the fruit fly brain to move two full hours ahead of its original schedule through a process known as “phase retuning.”
Phase retuning, the authors explained, is marked by a circadian circuit-wide pattern of short-term desynchronization followed by the gradual emergence of an internal clock that is back in rhythm. They propose that temporarily weakening synchronization among neurons governed by circadian patterns would allow people to adapt up to two days faster to the cues of their new time zone.
Shifting with the pulse of a light
That would cut jet lag recovery in half, Holmes said, as circadian circuit light response typically takes place over the span of four days. A larger time shift, such as one experienced from flying to London from California, would most likely require a longer recovery period, he added.
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“That two-day difference is quite a bit if it means you feel great from the beginning of your arrival, say, in Italy,” Holmes noted. “You’re going to feel bad on the plane in any event, so it’s best to get the adjustment over with so you can enjoy your destination. I’m certain this will lead to treatments that’ll have a big impact on our travel practices.”
“This work illustrates in real time how the network of daily clocks in the brain adjusts to synchronize with the local light cycle,” added circadian biology expert Erik Herzog from Washington University in St. Louis, who was not involved in the research. “With extraordinary cellular resolution, the researchers show that some cells shift faster than others following a pulse of light. This might become a useful therapy in treating jet lag or the growing problem of ‘social jet lag,’ where people keep different schedules during the week than on the weekends.”
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