Fig 1. Schematic of the dynamical processes that occur within and between neural populations.

Gray circles are quantities associated with interactions between populations (i.e., a and b), while white circles are quantities associated with a population (i.e., a or b). Spike-rate fields ϕ_ab arriving at neurons of type a from ones of type b are modulated by the synaptic dynamics, and undergo dendritic dynamics to produce postsynaptic subpotentials V_ab. These contributions are linearly summed in the dendritic tree, eventually resulting in charging currents at the soma that give rise to the soma potential V_a, after allowing for capacitive effects and leakage. Action potentials generated at the axonal hillock are averaged over a population of neurons. Then, when the mean soma voltage exceeds a threshold, the mean firing rate Q_a of the population is obtained via a nonlinear response function. Finally, the pulses propagate away across the axonal tree and the dendrites of the receiving population c as the set of average spike-rate fields ϕ_ca. Note that self-connections with b = a or c = a are included.