在双脉冲光刺激下瞳孔系统的采样控制特性

本文用实验揭示了瞳孔对光动态反应具有采样控制特性。实验中采用各种不同时间间隔的双脉冲光,以开环的方式(Maxwellian View)刺激瞳孔,当双脉冲之间间隔较长时,瞳孔反应相当于对双脉冲光的两次脉冲分别产生瞬态收缩;当双脉冲时间间隔短于0.6s 时,其反应就成了一次瞬态收缩,与单个光脉冲所引起的瞳孔反应一样。同—受试者的多次实验结果相同,不同受试者所得结果也基本一致。故瞳孔对脉冲刺激光引起反应后,必须至少约隔0.6s 才能对另一次脉冲光产生反应,这就说明了瞳孔动态反应具有离散的采样控制特性。实验还进一步证明,瞳孔系统的控制机制是双重模式的控制:不同的刺激条件下,瞳孔反应可呈现为瞬态反应(AC)或持续反应(DC),瞬态反应的 AC 通道为离散的采样控制,持续反应的 DC 通道为连续控制。

SAMPLING PROCESS IN PUPILLARY RESPONSE TO DOUBLE PULSE LIGHT STIMULI

Sampling data behavior of the pupillary control system was explored withexperiments of pupillary responses to light stimuli in open loop condition(Maxwel-lian View).When double-pulse low intensity light stimuli with the separationlonger than 0.6 seconds were applied,the pupillary responses normally resulted in adouble transient contractions.When the separation between the two pulses was shor-ter than 0.6 s,a single transient contraction similar to those obtained for singlepulse stimuli was found.The same results were obtained from different runs ofexperiments either in the same subject or from five different subjects.It meansthat a minimum period about 0.6 s is always required for the pupillary responseto the second pulse light stimulus following the first response.It the reveals thatdynamic behavior of the pupillary system is a discrete sampling control process.Furthermore,the pupillary responses were transient(AC)with low intensityof pulse stimuli,and were sustained(DC)with high intensity.Therefore the pupil-lary 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.