Simulating the continuum of pathological change.

<p>(<b>A</b>) Summary of <i>I</i>_stim thresholds to elicit onset-only or repetitive spiking for different values of β_w in our standard 2-D model. Reduction in threshold equates with an increase in excitability. Summary of peak MPO power (<b>B</b>) and peak frequency (<b>C</b>) across a range of β_w values. All simulations included noise. For each β_w value, <i>I</i>_stim was chosen relative to the threshold for repetitive spiking: <i>high</i> and <i>low I</i>_stim were 1.3 and 4 µA/cm² below threshold, respectively. Those values were chosen in order to include or exclude, respectively, noise-independent MPOs when a supercritical Hopf bifurcation occurs. Peak MPO amplitude and frequency decreased as β_w was increased. That trend is not attributable to noise-independent MPOs occurring at certain β_w values since noise-independent MPOs were excluded when testing with <i>low I</i>_stim (see above). Moreover, re-setting γ_m from 18 mV to 15 mV prevented the supercritical Hopf bifurcation from occurring at any β_w, but the same trend in MPO power and frequency was observed (data not shown). Dotted curve in C shows minimum sustainable firing rate. * indicates data points that include a noise-independent MPO component.