The term inferior frontal gyrus refers to a convolution of the frontal lobe identified by dissection. In the human it is located on the lateral surface between the inferior frontal sulcus, which separates it from the middle frontal gyrus, and the lateral fissure, which separates it from the superior temporal gyrus and insula. Caudally it is separated from the precentral gyrus by the inferior precentral sulcus ( Ono-1990 ). It extends rostrally to the orbital gyri. In the macaque it extends from the inferior ramus of the arcuate sulcus to the frontal pole; it is defined by the principal sulcus, which separates it from the middle frontal gyrus dorsally and by an arbitrary boundary with the fronto-orbital gyrus ventrally. Equivalent structures are not found in the smooth cerebral cortex of the rat or mouse ( NeuroNames ).