p073fig02.21 How shunting saturation turns on all of a cell's excitable sites as input intensity increases.<BR>||  Shunting saturation. At equilibrium:<BR>0 = d[dt: xi] = -A*xi + (B - xi)*Ii<BR>xi = B*Ii / (A + Ii) = B*θi*I / (A + θi*I) -> B as I -> ∞<BR>Ii = θi*I, I = sum[j: Ij]<BR>I small: lost in noise;  I large: saturates<BR>Sensitivity loss to relative intensity as total intensity increases.