Potentials and Limitations of Noise Analysis of Light-induced Conductance Changes in Photoreceptors

Abstract

The potentials and limitations of noise analysis applied to light-induced currents in photoreceptors are discussed in this paper. Two limiting cases are presented for which noise analysis may yield some reliable information on the underlying mechanisms. The “bump approach” is based upon the assumption that the “elementary events” underlying the noisy current are the quantum bumps which obey Poisson statistics. From the experimentally observed power spectrum of the noisy current one then draws conclusions for the properties of the single bumps, including their variation under different conditions of light adaptation. The method is usually extended to values of the stimulating light intensity for which single bumps are no longer directly observable due to light adaptation.