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.

Stability of intrinsic electrical activity and modulation of input-output gain are both important for neuronal information processing. It is there-fore of interest to define biologically plausible parameters that allow these two features to coexist. Recent experiments indicate that in some biological neurons, the stability of spontaneous firing can arise from coregulated expression of the electrophysiologically opposing I A and I H currents. Here, I show that such balanced changes in I A and I H dramatically alter the slope of the relationship between the firing rate and driving current in a Hodgkin-Huxley-type model neuron. Concerted changes in I A and I H can thus control neuronal gain while preserving intrinsic activity.