[Sampling process in pupillary response to double pulse light stimuli].

Sampling data behavior of the pupillary control system was explored with experiments of pupillary responses to light stimuli in open loop condition (Maxwellian View). When double-pulse low intensity light stimuli with the separation longer than 0.6 seconds were applied, the pupillary responses normally resulted in a double transient contractions. When the separation between the two pulses was shorter than 0.6 s, a single transient contraction similar to those obtained for single pulse stimuli was found. The same results were obtained from different runs of experiments either in the same subject or from five different subjects. It means that a minimum period about 0.6 s is always required for the pupillary response to the second pulse light stimulus following the first response. It the reveals that dynamic behavior of the pupillary system is a discrete sampling control process. Furthermore, the pupillary responses were transient (AC) with low intensity of pulse stimuli, and were sustained (DC) with high intensity. Therefore the pupillary system control can be interpreted in terms of a dual mode control mechanism: the transient (AC) part exhibits a discrete sampling behavior, while the sustained (DC) part shows continuous feedback control.