THE RECEPTIVE FIELDS OF OPTIC NERVE FIBERS

Abstract

Characteristics of the receptive fields of individual optic nerve fibers from the peripheral retinas of cold-blooded vertebrates (frog, alligator) have been investigated by recording the action potentials in single fibers. In several expts. the distr. of sensitivity over the receptive field of a particular fiber has been detd. by systematic exploration of the retina with a small spot of light, noting the responses elicited in the fiber at various locations. The sensitivity to light, referred to a particular optic nerve fiber, is maximal over the central portion of the fiber''s receptive field, and is less the greater the distance from this central region, usually becoming inappreciable outside an area about 1 mm. in diam. Single optic nerve fibers respond to sudden, slight movements of a small illuminated spot, or to a narrow band of shadow on the uniformly illuminated retina, if the moving spot or shadow falls within the receptive field of the fiber. These expts. prove that the receptive field of an optic nerve fiber from the peripheral retina covers an area much greater than that occupied by a single rod or conc. A retinal ganglion cell can receive excitatory influences over many convergent pathways; its axon is the final common path for nervous activity originating in many sensory elements. Action potentials recorded from small bundles containing many active optic nerve fibers show that a single small spot of light excites many fibers: the receptive fields of different fibers overlap considerably. The particular fibers activated, and the distr. of activity among them, is characteristic of the location on the retina of the particular element of area illuminated.