The site of electrical excitation of the human eye.

Sadao Yaegashi (八 重 樫 定 夫) From the Department of Physiology, Iwate Medical College, Morioka; Director: Prof. T. MitA (Received for publication, September 30, 1957) If the threshold voltages of alternating currents passing through the head, as determined with flickering phosphenes as an index of excitation, are plotted as a function of frequencies, there is found a distinct minimum at a frequency around 20 cps on the electric threshold strength-frequencycurve provided that measurements are made with the partially lightadapted eye. Barnett1) stated that this frequency around 20 cps should be the optimum frequency for electrical stimulation of those portions of the optic tracts connected to cones. But against his inference, much work has been done to ascribe the changes in electrical excitability of the eye for 20 cps to rod mechanism. Mita and Abe2) and Abe3), studied the effects of dark adaptation upon the electric threshold for square waves of 20 cps. They maintained that 20 cps may be the optimum frequency for electrical stimulation of those neural elements connected to rods. This view was supported by Meyer-Schwickerath4) from location of flickering phosphenes at the periphery of the retina. Motokawa and Ebe5) investigated by means of Motokawa's ƒÄ-value the resonance curve and the spectral response curve, and they confirmed that the frequency of alternating current at 20 cps. must surely be concerned with the rod mechanism. Yonemura and Nango6) found an important fact that a single rectan