The Orbital part of inferior frontal gyrus is the part of the inferior frontal gyrus named opercularis (literally "the part that covers") because it covers part of the insula. The pars opercularis together with the pars triangularis form the Broca's area, a neuroanatomic region important in speech-language production.
In the human, this region occupies the triangular part of the inferior frontal gyrus and, surrounding the anterior horizontal limb of the lateral sulcus, a portion of the orbital part of the inferior frontal gyrus. Bounded caudally by the anterior ascending limb of the lateral sulcus, it borders on the insula in the depth of the lateral sulcus. Cytoarchitectonically it is bounded caudally by the opercular area 44, rostrodorsally by the area 46 of Brodmann (human) and ventrally by the area 47 of Brodmann (human) (Brodmann-1909).
Syudo Yamasaki et al. (1 September 2010) found that a significant gray matter volume reduction of both the pars opercularis and triangularis was found bilaterally in the subjects with Aspergers/Autism compared with typical control subjects. The effect size seemed to be larger for pars opercularis (1.25) than for pars triangularis (.90). The reduced volume of right as well as total pars opercularis showed a significant association with the increased severity of social communication problems in the Aspergers/Autism group.