Temporal shaping of auditory responses by cortical inhibition. (A) A brief delay of inhibition narrows the time window for membrane depolarization, resulting in spikes with high temporal precision. (Left) Relative timing of model tone-evoked excitatory (red) and inhibitory (blue) inputs. Dashed line indicates the onset. (Middle) Derived membrane potential response resulting from excitation alone (top) or from the interplay of excitation and inhibition (bottom) using a simple neuron model. Dashed line indicates the spike threshold. Vertical lines mark the time window for spike generation. Vm, membrane potential response; Vr, resting membrane potential. (Right) Derived spike responses to tones in different trials. (B) Varying the onset of inhibition modulates the response of the cortical neuron, a mechanism underlying intensity selectivity. (Left) Blue curve 1 represents the inhibitory response to tone of optimal intensity, whereas 2 represents that to tone at higher intensity. (Middle) The derived membrane potential response to tone at higher intensity is weaker than that at optimal intensity. (Right) A simulation result showing the relationship between the peak amplitude of membrane potential response and the relative delay of inhibition. (C) Preceding inhibition silences spike output of the cortical neuron. (Left) Similar excitatory and inhibitory synaptic inputs as in A and B, except that the onset of inhibition is 2 ms earlier than that of excitation. (Middle) The derived membrane potential response is lower than the spike threshold. (Right) The expected post-stimulus spike–time histogram (PSTH) in response to a tone. The spontaneous firing is suppressed during tone stimulation.