A schematic diagram of the six layered mammalian neocortex. The lamination of the basic circuit with elaboration of the excitatory pyramidal neuron into specialized intratelencephalic (IT), pyramidal track (PT), and corticothalamic (CT) neurons. ffexc: feed forward excitation, fbexc: feed back excitation, lexc: lateral excitation, ffinh: feed forward inhibition, fbinh: feedback inhibition. Figure 2(C) from “Neocortical Lamination: Insights from Neuron Types and Evolutionary Precursors” published November 7, 2017 in Frontiers in Neuroanatomy.