The effects of 10-min light pulses on the timing of wheel-running activity in the nocturnal flying squirrel Glaucomys volans kept under constant darkness. The pulse delivered at the time of activity onset on day five caused an obvious delay in the subsequent phase of wheel-running.  The pulse delivered just after the daily bout of activity on day 15 resulted in no obvious change in phase.  From P.J. De Coursey (1960) Daily Light Sensitivity Rhythm in a Rodent.  Science. Vol. 131, pp. 33-35