抄録
When a portion of retina is stimulated by light, the areas surrounding the stimulated part undergo a change in excitability. The author has studied this phenomenon under various conditions. In the present research, it has been investigated through the measurement of visual utilization time of a small light spot. The main results may be summarized as follows:
1) When the dark adapted eye with an artificial pupil is given a weak light stimulus, the regions near the stimulated point become excitable. This phenomenon had better be called “the first phase facilitation”. As time elapses, however, the amount of facilitation falls gradually to zero, and then, nhibition occurs. It increases by degrees and reaches its maximum at about the moment of the removal of light stimulus. After that, as time passes, gradual diminution of inhibition follows and then there is a return to the normal state. Then, unexpectedly, the normal state is immediately broken and slight facilitation appears again. This may be called “the second phase facilitation”.
2) The shifting course of “facilitation-inhibition facilitation” is the fundamental type of variation inretinal excitability, which is found in all the present experiments. The experimental variables, such as the exposure time of the inspection light stimulus, brightness of the stimulus, the spatial distance between the inspection figure and the test patch, and so on, do not change the above-mentioned standard shifting course.
3) Within a certain extent, the brighter the light stimulus is, the less the amount of facilitation and the greater the amount of inhibition becomes. Even if the exposure time of the inspection light stimulus is made longer, it can produce the same effect as the above-mentioned effect.
4) In retinal areas remote from the point of stimulation, the process of “facilitation-inhibition-facilitation” takes place, too. But both facilitation and inhibition are less in amount there than at the parts nearer to the point stimulated.
These results are useful to set up a new hypothesis which will be able to account for Köhler-effect, tau-effect and many other phenomena of perception.
