Criticality analyses showing the effect of strong perturbations.

<p>A) The power law exponent <i>λ</i> was estimated during network evolution for a sliding time-window, then further grouped into a sliding window of <i>λ</i> estimates in order to show histograms changing over time. The network settles into critical behavior with PABA as shown in the top left inset (<i>t</i> = 200 s, <i>λ</i> = −1.5415, <i>R</i>² = 0.9998, <i>p</i> < 0.001). During the perturbation the network goes into a super-critical regime as shown in the second inset (<i>t</i> = 500 s, <i>λ</i> = −1.8851, <i>R</i>² = 0.9967, <i>p</i> < 0.001) with <i>λ</i> for the initial part of the distribution between −1.75 and −2, but with a concentration of larger avalanches. The network returns to criticality after the perturbation as in the bottom right inset (<i>t</i> = 600<i>s</i>, <i>λ</i> = −1.5592, <i>R</i>² = 0.9991, <i>p</i> < 0.001). B) Estimated deterministic dynamics for the firing rate of the network. Data for firing rates over 150 Hz come entirely from the first 500 ms of the simulation (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1004043#pcbi.1004043.g002" target="_blank">Fig. 2b</a>), where the network goes through a period of stabilization. Rates between 50 and 150 Hz are due to external perturbation, with an evident fixed-point near 100Hz. Otherwise, the network settles into a fixed point near 30 Hz (inset). C) The branching ratio <i>σ</i>. The two insets show <i>σ</i> during a perturbation and after recovery. The latter inset should be compared to <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1004043#pcbi.1004043.g002" target="_blank">Fig. 2c</a>, to see that branching ratio dynamics return to the same qualitative state. D) The distribution of scaling exponents <i>α</i> for 1000 neurons. All exponents lie between 0.5 and 1.0, indicating correlated fluctuations. The bulge in the tail of the distribution for 0.6 < <i>α</i> < 0.85 is due to the change in structural connectivity caused by STDP after the three perturbations.