Figure 3. Modulation of Neuronal Gain through an Interaction of Membrane Potential and Intrinsic Nonlinearities in Input-Output Transformation of Cortical Neurons.

(A) In the absence of neuronal variance, neurons respond to depolarization with an abrupt increase in firing rate once threshold has been reached (black). However, in the presence of membrane potential variance, the average relationship between firing rate and membrane potential can exhibit a power law (red).

(B) Intracellular recordings of cortical neuronal responses to visual stimuli in vivo have revealed, on average, a power law relationship between membrane potential and firing rate.

(C) In the presence of a power law relationship between membrane potential and firing rate, changes in either excitatory or inhibitory background conductance that depolarize or hyperpolarize neurons (±2–5 mV), respectively, can result in multiplicative-like changes in the input-output relationship of cortical neurons.

(D) Depolarization induced through the intracellular injection of current results in a multiplicative-like change in the contrast response function curve of visual cortical neurons.

(E) Scaling the hyperpolarized curve from (D) with a constant gain factor reveals a multiplicative-like gain change. (F) Depolarization that occurs spontaneously owing to synaptic bombardment in vivo can also result in multiplicative-like increases in neuronal responsiveness of the contrast response function.

(B) Adapted by permission from Macmillan Publishers Ltd: Nature Neuroscience (Priebe et al., 2004), copyright 2004; (C) modified from Murphy and Miller (2003); (D) modified from Sanchez-Vives et al. (2000); (E) modified from Haider et al. (2007).