Figure 2.

The influence of compartment size and channel density upon firing rate and information coding. (A) Top: An example of the excitatory conductance stimulus. Middle: An example of a spike train evoked by the conductance stimulus. Bottom: Spike rasters across 60 trials in response to presentations of identical conductance waveforms. (B) The spike rates in model cells receiving excitatory synaptic inputs for voltage-gated Na⁺ and K⁺ channel densities from a quarter of to four times the density of those found in the squid giant axon. Cells varied in diameter from 0.6 to 9.8 μm (equivalent to 1 to 300 μm² compartments). Colors and symbols indicate the density of the voltage-gated ion channels. (C) The information rates of each of the model cells shown in B. (D) A contour plot showing how the coding efficiency in bits/spike depends upon cell diameter and firing rate for all the compartments modeled (including those in Supplementary Figures S1 and S3). The data points have been fitted using locally weighted linear regression.