Figure 1.

The pupillary light reflex. (A) Neural circuits involved in the pupillary light reflex. (B) Responses of various species to light stimulation of the left eye. In rabbits, which lack many decussating optic axonal fibers, unilateral light stimulation produces no consensual light reflex in the contralateral eye (dashed lines). In contrast, species which have more decussating than non-decussating fibers have either imperfect consensual reactions to unilateral light stimulation (cats) or symmetric direct consensual reactions (monkeys). Duration of the light stimulation is indicated by the rectangular “light” period in each plot. Reprinted with permission from Kardon (2005).