Ubiquity of collective irregular dynamics in balanced networks of spiking neurons

We revisit the behavior of a prototypical model of balanced activity in networks of spiking neurons. A detailed study of an appropriate thermodynamic limit for fixed density of connections shows that, when inhibition prevails, the asymptotic regime is characterized by a self-sustained irregular, macroscopic (collective) dynamics rather than being asynchronous. This holds true even for very small coupling strengths. A relationship with the collective chaos observed in standard (unbalanced) heterogeneous networks is also put forward and the role played by clustered states discussed.