The parietal operculum is the portion of the parietal lobe on the outside surface of the brain bordering the lateral sulcus, and the extension of this cortex which forms the posterior ceiling of the lateral sulcus. It contains the secondary somatosensory cortex (region S2).
In monkeys, apes and hominids region S2 is divided into several "areas". In humans, the area adjoining the primary somatosensory cortex (S1) is called the parietal ventral area (PV). Adjacent to PV, but towards the posterior of the parietal operculum, is area S2 - which must not be confused with region S2 (which designates the entire secondary somatosensory cortex, of which area S2 is a part). Deeper in the lateral sulcus, bordering areas PV and S2, lies the ventral somatosensory area (VS). In humans, the parietal operculum includes parts of Brodmann areas 40 and 43.
Areas PV and S2 both map the body surface. Functional neuroimaging in humans has revealed that in areas PV and S2 the face is represented nearest the entrance to the lateral sulcus, and the hands and feet deeper in the fissure, nearer the border with VS. Individual neurons in areas PV and S2 receive input from wide areas of the body surface (they have large "receptive fields"), and respond readily to stimuli such as wiping a sponge over a large area of skin.
Areas S2 in the left and right hemispheres are densely interconnected, and stimulation on one side of the body will activate area S2 in both hemispheres. Area S2 is interconnected with Brodmann area (BA) 1, and densely so with BA 3b, and projects to PV, BA 7b, insular cortex, amygdala and hippocampus. PV connects densely with BA 5 and the premotor cortex.[1][2]
It was observed, post-mortem, that Albert Einstein was without this section of the brain and that adjacent areas were enlarged.[3]
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