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to voltage noise in the photoreceptor through the membrane resistance. The output voltage
variance is given by:
vuc = R2mio (5.21)
In the coupled rod network, current fluctuations in a rod are distributed through the
network according to the impulse response.
∞ ∞
υl = ∑ ∑ ⅛ (5.22)
TTl=-OO Tl=-OO
where ‰,n is the steady-state impulse response function of the rod network (as in figure
5.5).
For a hypothetical current noise of unit variance, the output variances and standard de-
viations for the uncoupled and coupled cases are:
vUC - R-m - 0∙09
f^UC “ Rjτn ~ 0∙3
υ2c = 0.02
υc = 0.15
Because of the signal averaging due to coupling, the baseline noise of the coupled net-
work is half the noise of the hypothetical uncoupled network. The signal-to-noise ratio is the
output amplitude divided by the noise standard deviation, so with whole field stimuli, the