exogenous zeitgebers

• p: the important role played by melanopsin in setting the circadian rhythm is demonstrated in studies of blind people

  E: some blind people are still able to reliably entrain their circadian rhythm in response to light despite a total lack of image forming visual perception. skene and arendt estimate that the vast majority of blind subjects who still have some light perception have normally entrained circadian rhythms
• link for melanopsin

  L: this suggests that the pathway from retinal cells containing melanopsin to the SCN is still intact. as further evidence for the importance of this pathway in setting the biological clock, people without light perception show abnormal circadian entrainment
• P: an application of research on exogenous zeitgebers comes from burgess, who found that exposure to bright light decreased the time needed to readjust to local time on arrival

  E: volunteers participated in one of 3 treatments, each of which shifted their sleep wake cycle back by 1 hour a day over 3 days. participants exposed to continuous bright light shifted their circadian rhythm by 2.1 hours. those exposed to intermittent bright light shifted their rhythm by 1.5 hours and third group exposed to dim light shifted theirs by 0.6 hours.
• link for avoiding jet lag

  L: this suggests that light exposure prior to a flight would allow travellers to arrive with their circadian rhythms already partially re-entrained to local time