An analogue simulation of the luminosity-channel in the vertebrate cone retina. 2. Frequency analysis.

A frequency analysis was performed on an analogue model of the vertebrate cone retina. Bode plots of magnitude and phase angle shifts were obtained from the various stages of the Model. While the cones were non-linear, the rest of the Model was linear and results could be explained by cascading of low-pass filters with linear summation of antagonistic inputs of differing time constants. The cut-off frequency of the Model was determined by the first stage, which was the cone pedicle, while the slope of the db magnitude versus frequency curve increased for each "synaptic delay" in the pathway. An initial increase in the magnitude of the output voltage at any given stage occurred up to the cut-off frequency and was due to the antagonistic input voltages of differing time courses. Physiological data were discussed in terms of the Model.