Figure 6. Role of active conductances in balancing depolarization- and hyperpolarization amplitudes.

Passive models can only achieve a hyperpolarizing shift of of the depolarization due to different driving forces caused by the synaptic reversal potentials. We optimized passive and active models as before but demanded a balance between the depolarization and hyperpolarization shifts so that the depolarization amplitude had to be of the hyperpolarization amplitude. None of the optimized passive models exhibited the desired membrane shifts (typical model illustrated in A), while all active models exhibited the demanded membrane shifts (typical model illustrated in B). Therefore, this result follows our hypotheses that active conductances are required in VS cells to achieve biologically realistic balancing between responses in preferred- and null-direction.