Fig 1. Model of neural encoding with three sources of noise.

A: Model schematic for a single pathway. An input s is directly corrupted by some noise η, and then transformed nonlinearly by f(⋅). The nonlinear processing stage sets the mean of a scaled Poisson response with variance equal to κ times the mean response. This response is corrupted by additional additive downstream noise ζ to give a total response r. B: Transformed stimulus distribution at each stage of the model. C: Model schematic for two parallel pathways. Noise upstream and downstream of the nonlinearity may be correlated across neurons. For schematic purposes, we have drawn all signal processing steps as though they are contained within a single neuron, but each pathway could more generally represent signal processing spread out across multiple neurons.