The Canonical Microcircuit (CMC) neural mass model . This figure shows the evolution equations that specify a CMC field model of a single source. This model contains four populations occupying different cortical layers: the pyramidal cell population of the Jansen and Rit (JR) model is here split into two subpopulations allowing a separation of the sources of forward and backward connections in cortical hierarchies. As with the JR model, second-order differential equations mediate a linear convolution of presynaptic activity to produce postsynaptic depolarization. This depolarization gives rise to firing rates within each sub-population that provide inputs to other populations.