Level dependent signal flow in the light pupil reflex. III. Phase velocity in high gain instability oscillations.

The pupil can be excited to sustained oscillations under high gain feedback conditions. The period of these oscillations (cycle time) is reduced by increased average light level by an amount commensurate with reductions in phase lag reported in the companion paper (Myers et al. 1991b). A mathematical model of this phenomenon is used to unify and clarify experimental data presented here and in the literature.