Flash Stimulation Of The Circadian Visual System

Main Category: Neurology / Neuroscience
Also Included In: Sleep / Sleep Disorders / Insomnia
Article Date: 31 Mar 2007 - 6:00 PDT

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The mammalian -1ber-clock in the supra-chiasmatic nucleus (SCN) sets the circadian rhythm based on photic input received over the day/night cycle. Resetting the clock with light stimulation occurs after continuous pulses, in which phase shifts result from integration or "photon counting" of long, relatively dim light pulses.

However, as Vidal and Morin show this week in hamsters, brief trains of millisecond-long intense light flashes can cause significant phase shifts. Hamsters exposed to as few as three 2 ms light flashes over a 5 min or even a 60 min period displayed nearly all-or-none phase shifts, although 10 or more flashes produced more consistent and robust results.

The shifts required an irradiance threshold of 140 :IW/cm2, an interflash interval of not shorter than a few seconds, and were accompanied by increases in the immediate early gene FOS in the SCN and beyond. Might be good news for jet-lag sufferers.

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Luis Vidal and Lawrence P. Morin

Source: News tips from the Journal of Neuroscience

Contact: Sara Harris
Society for Neuroscience

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