Period focusing induced by network feedback in populations of noisy integrate-and-fire neurons

The population dynamics of an ensemble of nonleaky integrate-and-fire stoch astic neurons is studied. The model selected allows for a detailed analysis of situations where noise plays a dominant role. Simulations in a regime w ith weak to moderate interactions show that a mechanism of excitatory messa ge interchange among the neurons leads to a decrease in the firing period d ispersion of the individual units. The dispersion reduction observed is lar ger than what would be expected from the decrease in the period. This "peri od focusing" is explained using a mean-field model. It is a dynamical effec t that arises from the progressive decrease of the effective firing thresho ld as a result of the messages received by each unit from the rest of the p opulation. A back-of-the-envelope formula to calculate this nontrivial disp ersion reduction and a simple geometrical description of the effect are als o provided.