Generative model of spike-LFP coupling.

(A) A two-population neural field model of neural dynamics. V_k, λ_k and s_k indicate respectively somatic membrane potential, firing rate and post-synaptic current for Excitatory (k = E) and Inhibitory (k = I) populations. η indicates the exogenous input to the circuit. Arrows indicate the causal dependence between variables of the model. (B) Schematic representation of the model’s connectivity: local inhibition and long range excitation, together with the driving by exogenous synaptic currents. (C) Schematic representation of the contribution of postsynaptic currents to the electric field, affected by the spatial distribution of synapses over the dendritic tree and the geometry of pyramidal cells. From left to right: Schematic representation of pyramidal neurons, electric field, electrode (gray bar), contribution of each current (EPSC, IPSC and exogenous current, leak current is also contributing to LFP but is not shown) to the LFP profile along the electrode’s axis (D) Simple microcircuit structure leading to a temporal ordering of the local activities of different kinds LFP → excitation → inhibition (E) Simple microcircuit structure leading to a temporal ordering of activities of the same kind across space: the location receiving stronger exogenous input leads other locations, such that amplitude gradient leads to phase gradients.