A Functional Study of the Nerve Elements of the Optic Pathway by Means of the Recorded Action Currents

Abstract

Records have been made of the small output of electricity that is the result of the activity of a nervous element; they form an index of such nervous activity, being subject to analysis as to the response of distinct groups of fibers in the nerve. The optic tract responds to stimulation of the retina by a beam of light in characteristic fashion. The response of the optic nerve is by a series of impulses relative to the intensity and duration of the beam, after a latent period. The summation of these impulses in the thalamus sets off an impulse to the cortex, again after a latent period. The cortex gives at least two types of electrical response. Any one pathway seems to be conducting only part of the time, due to the independently rhythmic activity of the thalamus, which is therefore periodically nonirritable to optic-nerve impulses. The optic cortex, also independently rhythmically active, responds characteristically to optic-nerve stimulation. In the authors' opinion, the act of seeing is a disturbance of the individual pattern of visual-cortex activity, rather than the superimposition of a new activity of different type upon it. From the Laboratory of Neurophysiology, Oscar Johnson Institute, Washington University. Read before the Association for Research in Ophthalmology, in Cleveland, June 12, 1934.