SLOW POTENTIALS INDUCED FROM THE ILLUMINATED PART INTO THE SURROUNDING AREA OF THE RETINA

Abstract

Responses of the inverted carp's retina to focal illumination were recorded by means of a KCl-filled microelectrode about 1μ in tip diameter.1. Positive potentials were obtained from the illuminated part, and from the surrounding area potentials of similar shape, but of opposite polarity were obtained.2. One per cent solution of cocaine applied to the illuminated part abolished both kinds of potential. When the same solution was applied to a restricted area in the surrounding field, the negative potential recorded there increased in amplitude. This effect was attributed to suppression of a positive component caused by stray light.3. The spectral response curves of positive and negative potentials were obtained using monochromatic lights produced by interference filters (Lange and Co.). The monochromatic lights were made equal with respect to their energy. The spectral distributions of both potentials were almost identical, showing dominant peaks at 480 and 520m E and less conspicuous ones at 580 and 620mμ. The peaks at longer wave-lengths became predominant over those at shorter wave-lengths under strong light adaptation.4. The time-courses of positive and negative potentials were compared by the method of Lissajous' figure, and it was found that the development and subsidence of the negative potential were somewhat delayed.5. Negative potentials were recorded at various distances from the margin of the illuminated part and their latencies were determined. Conduction velocities thus obtained ranged from 67 to 160mm. a sec., averaging 112mm.a sec.6. The physiological mechanism of this phenomenon was discussed in comparison with similar phenomena in the cerebral cortex on one hand, with spreading induction in the human retina on the other.