Systems analysis of an analog model of the vertebrate cone retina

Systems analysis of an electronic analog of the generalized vertebrate cone retina using Laplacian transforms has generated time-dependent output voltages for various simulated retinal elements that are in agreement with experimental data. An electronic simulation of the author´s theoretical model of the vertebrate cone retina (J. Theor. Bio., vol.86, p.673-708, 1980) was constructed with each retinal element simulated by a linear summator to add input voltages and by a leaky integrator to stimulate `synaptic delay´. Antagonistic input voltages from cones and horizontal cells that have slower time courses are received by bipolar cells. Tonic ganglion cells are formed by direct output voltages from one of two types of bipolar cells, depolarizing-center (DPBC) and hyperpolarizing (HPBC), while phasic ganglion cells are formed via phasic amacrine cells that in turn receive their antagonistic input voltages from both types of bipolar cells with HPBCs having slower time courses. There is a dynamic balance between tonic and phasic channels that are dependent on the sum of center- and surround-field input voltages to bipolar cells. Negative feedback from horizontal cells to cones, and potentiation of negative feedback by electrical coupling of horizontal cells, have reinforced the effects of the surround field on the response characteristics of bipolar cells and thereby of subsequent retinal cells.