Shunting Inhibition Modulates Neuronal Gain during Synaptic Excitation

Mitchell, SJ. Silver, RA. (2003). Shuniting Inhibition Modulates Neuronal Gain during Synaptic Excitation. Neuron 38: 443-445.

Several studies have suggested role of shunting inhibition as multiplicative gain or additive effects. Several studies show that tonic shunting inhibition does *not* regulate gain of neurons. This study suggests that fluctuating inhibition, however, can act divisively.

Used dynamic clamp in granule cells to pass in both excitatory conductances and inhibitory conductances. With varying excitation and tonic inhibition get gain and a slight shift, with tonic excitation and inhibition get only a shift.

Mean voltage is independent of tonic excitation. However, with synaptic excitation mean voltage changes in relation to excitation rate.

The absolute variability and frequency dependence of excitation variability are important for neuronal gain reductions during inhibition. Having a faster excitatory time-constant results in a large gain effect (as the input has high variability), while slower time constant looks more like a tonic input and results in a more additive effect via shunting.

Synaptic-inhibition also influences the gain, and can even act as gain control with tonic excitation.