Abstract
Spatial summation and inhibition were studied with two methods, Motokawa's ζ-method and the binocular brightness match method.
1. The electrical excitability of the eye was measured after exposure to white five spots together and to the central spot of them alone. The excitability was greater for the five spots together (summation), when the distance between the centrally fixated central spot and other four spots was a few degrees in visual angle, but smaller (inhibition) when the distance was 8°-11°.
2. Distribution of summation and inhibition in the retina was mapped by exploring each region with 2 spots 3° apart from one another, and it was found that the central part of about 12° in diameter was a sum-mation area, which was surrounded by an inhibitory zone of 5° in width.
3. The rod process which was determined by the ζ-method, showed spatial summation, but no inhibition at all.
4. The effect of a glare patch G upon the brightness of a test patch T presented to one eye was measured in comparison with a control patch viewed by the other eye, and it was found that the inhibitory effect of G upon T was greatest when G was presented to the inhibitory zone of the retina determined by the ζ-method.
5. Under experimental conditions advantageous for scotopic vision no inhibition could be found by the brightness match method in accordance with the result obtained by the ζ-method.
