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. Author manuscript; available in PMC: 2012 Oct 22.
Published in final edited form as: Phys Rev E Stat Nonlin Soft Matter Phys. 2010 Nov 8;82(5 Pt 1):051911. doi: 10.1103/PhysRevE.82.051911

FIG. 3.

FIG. 3

(Color online) Top panel: the phase portrait of the mean-field model in the SO phase. The curves represent the nullclines of the calcium and somatic voltage equations. Their intersection, marked by the open circle, is an unstable fixed point of the dynamics. Trajectories not starting there evolve toward the limit cycle shown in red. Middle panel: the phase portrait of the mean-field model in the quiescent (Q) phase. Trajectories not starting at these fixed points evolve toward the one stable fixed point corresponding to a highly polarized membrane potential and low dendritic calcium concentration. Here the neurons do not fire. Bottom panel: the phase portrait of the mean-field model in the HA phase. Their intersection, marked by the filled circle, is a stable fixed point corresponding to a depolarized membrane potential and significant calcium concentration. This state corresponds to the case in which the neurons should typically fire repeatedly.