  Triggering a single additional spike in a cerebral cortical neuron was
recently demonstrated to cause a cascade of extra spikes in the network that is
likely to rapidly decorrelate the network's microstate. The mechanisms involved
in this extreme sensitivity of cortical networks are currently not well
understood. Here, we show in a minimal model of cortical circuit dynamics that
exponential state separation after single spike and even single synapse
perturbations coexists with dynamical stability to infinitesimal state
perturbations. We propose a unifying picture of exponentially separating flux
tubes enclosing unique stable trajectories composing the networks' state
spaces.
