Tuning low-voltage-activated A-current for silent gain modulation.

Modulation of stimulus-response gain and stability of spontaneous (unstimulated) firing are both important for neural computation. However, biologically plausible mechanisms that allow these distinct functional capabilities to coexist in the same neuron are poorly defined. Low-threshold, inactivating (A-type) K(+) currents (I(A)) are found in many biological neurons and are historically known for enabling low-frequency firing. By performing simulations using a conductance-based model neuron, here we show that biologically plausible shifts in I(A) conductance and inactivation kinetics produce dissociated effects on gain and intrinsic firing. This enables I(A) to regulate gain without major changes in intrinsic firing rate. Tuning I(A) properties may thus represent a previously unsuspected single-current mechanism of silent gain control in neurons.