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consistent with the observed response.
The model predicts that the incremental change in calcium current with the feedback is
too small to cause the observed depolarization in the cone membrane. It is only through the
calcium current’s effect on Ici(ca) that a large enough depolarization can occur. Because the
feedback requires the activity of the chloride current, the model also predicts that to observe
an inhibitory feedback response, that the cone must be hyperpolarized by a light stimulus to
generate enough driving force for the chloride current if Ecι is -43 mV [ 102]. This prediction
is consistent with our direct observations— cones must first be hyperpolarized with a center
stimulus before an antagonistic surround can be observed.