Local control of retinomotor activity in the fish retina

Abstract

Small circular spots of light were focussed on otherwise unilluminated retinas of paralyzed fish. Cichlasoma biocellatum. The retinas were subsequently examined histologically, and a small circular region was found within which the cones and pigmented retinal epithelium were photomechanically light adapted; rods could not be resolved. The same result was obtained with the optic nerve cut. The region was circular and about the same size as the adapting spot. There existed a transition zone between light- and dark-adapted regions within which the photomechanical state was intermediate. These results exclude the hypothesis that light-induced retinomotor phenomena are systemically controlled, and favor local control. An analysis of the transition zone favors the view that photomechanical light adaptation of a given cell may be caused by light caught by that cell or its neighbors.