Graded interactions between identified neurons from the simple eyes of an insect.

Intracellular recordings were made of anatomically identified second order neurons of the ocelli of the locust (Orthoptera, Acrididae), and the graded responses of individual neurons to illumination of the 3 ocelli were compared. It was found that two anatomical types of neurons responded with hyperpolarization to illumination of one ocellus, and with depolarization to illumination of another ocellus. The depolarizing responses were abolished with picrotoxin. The 3 anatomical types of large neurons in the median ocellar nerve had responses which were physiologically distinct.