p503fig13.29 The ON response to a phasic ON input has Weber Law properties due to the divisive terms in its equilibrium response, which are due to the habituative transmitter.<BR>||  ON-response to phasic ON-input.  S1 = f(I+J): y1 = A*B/(A+S1), T1 = s1*y1 = A*B*S1/(A+S1); S2 = f(I): y2 = A*B/(A+S2), T2 = s2*y2 = A*B*S2/(A+S2);.  ON = T1 - T2 = (A^2*B*(f(I+J)-f(I)) / (A+f(I)) / (A+f(I+J)) Note Weber Law. When f has a threshold, small I requires larger J to fire due to numerator, but makes suprathreshold ON bigger due to denominator.  When I is large, quadratic in denominator and upper bound of f make ON small.