Precuneus

At a glance

English

Precuneus

Latin (TA2)

Precuneus

System

Brain and spinal cord

Region

Head

Side

Paired, left and right

About the precuneus

The precuneus is the medial part of the parietal lobe, the continuation onto the inner face of the hemisphere of the superior parietal lobule. Its outline is roughly four-sided, which gave it the older name quadrate lobule of Foville. In front its limit is the upturned marginal ramus of the cingulate sulcus, which separates it from the paracentral lobule; behind, the parieto-occipital sulcus divides it from the cuneus; and below, the subparietal sulcus marks it off from the posterior cingulate cortex. Above, it reaches the superior border of the hemisphere.

Brodmann treated it as a single field, the medial extension of area 7, but connection studies show three zones. A front zone near the marginal sulcus links with sensorimotor regions, among them the paracentral lobule, the supplementary motor area and the insula. A central zone links with the angular gyrus and the lateral prefrontal cortex. A back zone near the parieto-occipital sulcus links with visual areas of the cuneus. Beneath the cortex it connects with the dorsal thalamic nuclei, including the pulvinar, and with the caudate, putamen, claustrum and parts of the brainstem.

Because it is buried in the midline and seldom damaged on its own, the precuneus was long poorly mapped, and much of what is known comes from functional imaging. It is active in visuospatial imagery and in steering attention to places in space, in recalling personal episodes and their context, and in thinking about oneself and taking another person's viewpoint. With the posterior cingulate cortex it is a central hub within the default mode network, the set of regions most active during quiet wakeful rest.

Its metabolism is among the highest in the cortex while awake and falls sharply under anaesthesia and in deep sleep, so it is linked with conscious awareness. Reduced metabolism in the precuneus and posterior cingulate is an early finding on PET scans in Alzheimer's disease. The region is proportionally larger in humans than in other primates.

Function and supply

Function

Supports visuospatial imagery, the direction of attention in space, recall of personal memories and self-reflection, acting as a hub within the default mode network.

Blood supply

The precuneal branch of the pericallosal (anterior cerebral) artery and the parieto-occipital branch of the posterior cerebral artery.