Information processing in the system from light to horizontal cell response of the carp retina

In this paper, two types of experiments in the carp retina are presented. One is the analysis of responses to white-noise-modulated light at different average mean intensity levels recorded from L-type horizontal cells. For weak light, the responses fluctuated symmetrically around mean values. For brighter light, however, the distribution of amplitude of the response departed from the normal distribution. The deviation from the normal distribution was characterized in terms of symmetry rather than peakedness. The deviation also implies the existence of a nonlinearity in the system. The other type is with barium ion. Ba2+ produced dramatic effects on the spectral response patterns of horizontal cells; the depolarizing response to long wavelength light of the R/G cell and the hyperpolarizing response to deep red light of the Y/RB cell were eliminated in Ba2+-containing solutions. The response of the L cell to white-noise-modulated light was also changed by application of Ba2+. In Ba2+-containing solution, the response became larger as well as slower than that in normal solution. The results of Ba2+ are discussed in relation to the interactions between cone and horizontal cells.