Interrelations and effects of the principal variables in the normalization model. A, Relation between membrane potential V and firing rate R . For simplicity in this study the resting potential is taken to be V = 0. The thick, intermediate, andthin lines depict rectification with thresholds V_thresh = 0, 6, and 12 mV, respectively. Thedashed curves indicate approximations to rectification obtained with power functions, with exponents n = 2 (thick dashes) and n = 3 (thin dashes). B, Relation between pool activity and membrane conductance. The abscissa plots the overall response of the pool, k Σ R ; the ordinate plots the increase in membrane conductance g/g₀ − 1 (Eq. 4).C, Effects of conductance on the size and time course of the membrane potential responses. The curves are the membrane potential responses to a current step with onset at time zero, for three different values of the conductance g . As the conductance doubles (thin to thick curves), it reduces both the gain and the time constant of the cell.