抄録
1. The latency of on-response was changed markedly by the changes of stimulus intensities, especially by the changes from 0.1 lux to 6 lux, and showed a large seasonal variation. The amplitude was changed in pro-portion to the log-intensity at least within a range from 0.1 lux to 1 lux, in winter toads.
2. The optic lobe off-responses were frequently absent even if on-responses appeared. The latency of the former was always shorter than that of the latter. But wave forms were almost the same in both cases. The optic lobe off-response seems to arise from the off-elements in the optic lobe, which receives neural impulses originated in the retina as post-inhibitory-rebounds.
3. From comparison of the latency and culmination time of optic lobe response with those of optic nerve and retinal responses the following relation was established: The latency of retinal b-wave ≤ the latency of optic nerve response < the latency of optic lobe response < the culmina-tion time of retinal b-wave. The latency of the retinal b-wave correspond-ed to 60 to 70% of that of optic lobe response. Accordingly it seems that the retinal process plays a dominant role in the change of latency of the visual process. These findings also suggest that the b-wave originats from the immediate precursor which sends the' impulse to the optic nerve.
4. The latency of optic lobe on-response in the course of dark adapta-tion showed a characteristic change which resembled the critical stage in the so-called perception time for light. These findings suggest that the evoked potential of the optic lobe is closely connected with the occurrence of the visual sensation and can be an objective measure for visual activity.
The author wishes to express his gratitude to Dr. Seizo Katsunuma and Hideo Toyoshima for their constant interest and guidance during this study, and to Mr. Koichi Otani for his invaluable technical assistance.
