A linear analysis approach has been applied to determine the dynamic characteristics of the color-coded S-potentials. Using a sinusoidally modulated light stimulus it could be shown that the monophasic S-potential as well as each of the different components of biphasic and triphasic S-potentials behaves linearly. However, for high modulation depths and high average intensities nonlinear effects, such as saturation, become obvious. The transfer characteristics of the monophasic potentials and each component of the biphasic and triphasic potentials are indistinguishable. Their latencies, however, differ. These findings suggest that the three different types of S-potentials not only originate from functionally comparable cells but also that the dynamic characteristics of the cells presynaptic to the S-potential sources are identical.In recent years much attention has been given to a curious type of graded response that has been found in the retinas of many vertebrates. These responses were described for the first time by Svaetichin (8) for the teleostean retina. The origin of these potentials is a point of controversy and in order to provide them with a biologically nonspecific name they have been named after Svaetichin and are called S-potentials. It can be said with certainty only that the S-potentials originate in the layers that lie between the photoreceptors and ganglion cells in the retina (1, 5, 9, 11).In the fish retina, three fundamentally different types of spectral response curves have been observed for the S-potentials. One type, the monophasic S-potential, is hyperpolarizing to all wavelengths between 400 and 750 nm. Another type of S-potential, the biphasic response, is hyperpolarizing to green and depolarizing to red stimuli. The third type of S-potential is a triphasic response, which consists of components that are depolarizing to green and hyperpolarizing to blue and red portions of the spectrum (6, 7).In a previous paper (7) it was demonstrated for the carp retina that the three S-potential types have identical spatial organizations, and therefore

The receptive fields of S-potentials have been studied in carp retinas. The relationship between the stimulus intensity and area of stimulation was examined for each component of three different types of S-potential. It appears that for each component there is full summation over a large portion of the retina, a type of organization different from that found in the ganglion cell.

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