Posterior part of the inferior frontal gyrus (pars opercularis), in the dominant (usually left) hemisphere. Bounded by the precentral sulcus posteriorly and the ascending ramus of the lateral sulcus anteriorly.

Dysgranular cortex — transitional between agranular area 6 (posteriorly) and granular area 45 (anteriorly). Layer IV is present but thin. Contains magnopyramidal cells in layer III. Pronounced intersubject variability in size (up to 10-fold volume difference between individuals). Leftward asymmetry in most right-handers.