The opercula (“little lids”) are the frontal, parietal and temporal edges of cortex that fold over the insula and hide it inside the lateral sulcus: the frontal operculum on the inferior frontal gyrus and the foot of the precentral gyrus, the parietal operculum on the lower postcentral gyrus, and the temporal operculum, the superior temporal gyrus, below. [1][2]
The 3D brain needs JavaScript. The text below still says where the opercula are and what they do.
Seen from the left: the four lit gyri meet around the lateral sulcus, and the yellow insula drawn through them is what their edges, the opercula, cover. The front (coronal) slice button cuts across, so you can see the lids folded over the insula. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
Lit: the whole inferior frontal, precentral, postcentral and superior temporal gyri, on both sides, with the insula they cover drawn through them in yellow. The area is part of these gyri; its exact border is not drawn. Each operculum is only the edge of its gyrus that faces the insula. The model draws each gyrus as one shape with no operculum of its own, so the four whole gyri are lit. [1][2][3]
A frontoparietal operculum covers the upper part of the insula from front to back and lies on the precentral and postcentral gyri, either side of the central sulcus. [1]
The circular sulcus (sulcus of Reil) is the semicircular groove that separates the insula from the opercular gyri in front, above and behind. [4]
The insula starts to fold inward at 14 to 16 weeks of fetal development; the opercula begin to form at 20 to 22 weeks and cover it completely by full term, a process called opercularization. [1]
The occipital operculum, part of the occipital lobe, shares the name but does not cover the insula and is not lit here. [1]
What it does
The opercular and triangular parts of the inferior frontal gyrus (Brodmann 44 and 45) make up Broca’s area; the opercular part is the part of the frontal lobe that overlies the insula. [5]
The secondary somatosensory cortex (S2) lies in the parietal operculum on the ceiling of the lateral sulcus; the face is represented near the entrance of the sulcus and the hands and feet deeper in. [7]
Buried on the upper face of the temporal operculum lie the transverse temporal (Heschl’s) gyri of the primary auditory cortex, the first cortex to process incoming sound. [8]
Connections
In human diffusion imaging, the anterior insula they cover is wired to the opercular cortex and to the triangular and opercular parts of the inferior frontal gyrus. [4]
Other names
Operculum is Latin for “little lid”; the plural is opercula. Together the frontal, parietal and temporal opercula are the opercula of the insula. [1]
Size
The model has no shape for the opercula itself, so it is not measured here. The whole left inferior frontal, precentral, postcentral and superior temporal gyri that hold it measure, together, about 131 mm front to back, 103 mm top to bottom and 69 mm side to side on this model (the box they fit in, not their volume). [3]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); real brains vary in size and shape, so its measurements describe one model, not anyone’s brain.