Collective bursting in populations of intrinsically nonbursting neurons

We describe a novel type of bursting that we observe in simulations of larg e recurrent networks of biophysically plausible, intrinsically non-bursting neurons. The mechanism responsible for the bursting is a combination of ex citatory feedback received from neighbouring neurons, together with an acti vity-dependent adaptation mechanism that slows down spiking. During the bur sting phases, the firing patterns are not repeated and the lengths of the i nterburst intervals are varying. We develop a simple phenomenological model that captures most qualitative aspects of the observed collective bursting . We compare the parameter range leading to bursting in the phenomenologica l model, with parameter estimates from cortical anatomy and physiology, and conjecture that the discovered new type of bursting should also be observa ble in biological neocortical networks.