Potential changes and eyelid microvibration elicited by flash stimulation.

The photopalpebral reflex evoked in the upper eyelid of the rabbit by flash stimulation was studied in terms of potential change (PPR) and microvibration (MV) and the following conclusions drawn. (1) Of the PPR components, the early components from PPR1 to PPR4 are mainly ERG components, while PPR5 to PPR9 and MV are components appearing via the central nervous system. (2) Excitation of the brainstem reticular formation is involved in the appearance of the central PPR components and MV. Components PPR6 to PPR8 and MV originate in excitation of the same nervous tissue, but PPR9 occurs by excitation of different nervous tissue. (3) Contraction of the extraocular muscles, as well as the orbicularis oculi muscles, is involved in the appearance of MV. (4) Unit discharge takes place in the brainstem reticular formation coinciding with the occurrence of MV and an increase in discharge takes place later. The relation of the increase in this late discharge to PPR9 must be further investigated.