Network firing activity during spontaneous and stimulated conditions.

<p>The network cohesion and inhibition levels are and , respectively. (<b>A</b>) Firing activity for network neurons (10 neurons in each population, as indicated on the right): raster plot (black) together with the mean rate (red curves) for each population, obtained as the convolution of the spike trains with a unit Gaussian function with 50 ms width. For the first 10 s, no stimulus is applied and the resulting ongoing activity is similar in all excitatory populations: in each of them, the firing rate fluctuates irregularly and abruptly as the result of input rate fluctuations and induced excursions between the different attractors of the network. Besides an attractor corresponding to low activation in all populations, there are attractors corresponding to higher activation in one selective population and low activation in all the others. From time s (green vertical line), a stimulus is presented to the selective excitatory population 1 ( Hz), increasing its mean rate and decreasing the one of the other selective pools. Moreover, all rates have now lower fluctuations: the attractor corresponding to a high activation of population 1 and a low activation of the others is stabilized. (<b>B</b>) Probability distribution of the rate fluctuations for the specific excitatory populations during spontaneous activity. The rate fluctuations are quite large (mean rate: Hz; standard deviation: Hz), with no peak except at zero rate and a long tail. This behavior reveals the excursion regime between the different attractors.