[The central basis of discrete sampling behavior in the human pupillary control system]

The human pupillary control system was investigated with double-pulse light dichoptic stimulation to explore its discrete sampling behavior. In this dichoptic stimulating method, the first pulse of the double pulse light stimulated one eye, of which the pupil area was recorded, and the second pulse stimulated the other eye (the contralateral eye). The experiment data demonstrated that the pupillary control system requires a minimum time interval, approximately 0.6 s, to elicit next transient response to the second light pulse, even though the two pulses were presented respectively to different eyes of the subject. The result supports the suggestion that the discrete sampling process exists in the pupillary control system. Moreover, it indicates that the minimum time interval is not caused by the retina adaptation, but determined by the central nerve system.