A retinal excitation gradient in a uniform area of stimulation.

Abstract
A method for testing excitation within a uniformly illuminated retinal area is descr. which consists of determining thresholds for a point source superimposed on a large stimulus area. Study of the dark-adapted peripheral retina of humans indicates a relationship between the intensity threshold for the point source and the distance from the center of the large area, threshold being lowest in the center of excitation. The present expt. provides direct confirmation of Graham, Brown and Mote''s hypothesis explaining the area-intensity relation in terms of interaction in the retina.