Role of synaptic feedback and intrinsic voltage-gated currents in shaping cone light responses

A model of the outer primate retina was used to investigate how cone light responses could be shaped by both synaptic feedback from horizontal cells and intrinsic voltage-gated conductances. Published data was used to estimate the photoconductance, convergence/divergence ratios, synaptic transfer functions, passive membrane properties and voltage-gated conductances, the latter using a Levenberg–Marquardt search algorithm. When the cone resting potential was sufficiently depolarized, synaptic feedback from horizontal cells could account for the flash response measured experimentally. Voltage-gated conductances were not significantly activated during the flash response but rather maintained the cone membrane potential inside a narrow physiological range.