Table 1. Parameters for Virtual Retina simulations representing midget cells in the foveal region of a primate retina (see ref. 15).

Parameter	Value	Comment
Outer Plexiform Layer
σC	0.05°	Centre gaussian’s sigma
τC	10 ms	Centre signal low pass filtering time constant.
τU	100 ms	Undershoot high pass filtering time constant.
wU	0.8	Undershoot transient relative weight.
σS	0.15°	Surround gaussian’s sigma
τS	4 ms	Surround signal low pass filtering time constant.
λOPL	10 Hz/Lum. unit	Overall gain of the centre-surround filter.
wOPL	1	Relative weight of centre and surround signal.
Use leaky heat equation	True	Averaging by gap junctions rather than dendritic spread. Leads to a non-separable spatio-temporal filter, but somewhat more realistic.
Bipolar Cells
λOPL’	50	Another gain applied right after λOPL, thus without biological meaning, but useful for implementation issues.
gA0	50 Hz	Inert leaks in membrane integration.
σA	0.2°	Size of the spatial neighbourhood used to estimate local contrast.
τA	5 ms	Size of the temporal neighbourhood used to estimate local contrast.
λA	0 Hz	Strength of the gain control feedback loop (no contrast gain control in primate midget cells)
Inner Plexiform Layer
τG	20 ms	High pass filtering time constant.
wG	0.7	Transient relative weight.
σG	0°	No additional pooling for midget cells.
vG0	0	Bipolar linear threshold.
λG	100 Hz	Slope in the linear area.
iG0	37 Hz	This is below the threshold current (50 Hz). Thus in the dark the threshold is reached only because of the noise (see below), which leads to a irregular Poisson-like spontaneous activity (at ~1 Hz).
Retinal Ganglion Cells (RGC)
gL	50 Hz	Leak conductance (thus the membrane time constant is 20 ms)
σv	0.1	Gaussian white noise current’s normalized amplitude. Integration of this current by the RGCs leads to a Gaussian auto-correlated process with time constant 1/gL and variance σv.
ηrefr	3 ms	Refractory period
Density	20 cells/°	RGC density (for each polarity). That is a mean inter-RGC interval of 0.05°