Precuneus

Sensorimotor Anterior Region

This occurs around the margin of the cingulate sulcus (  blue in figure) and is connected with sensorimotor areas of the cerebral cortex such as the paracentral lobule, supplementary motor area, premotor cortex, somatosensory area (Brodmann area 2), parietal operculum and insula. fMRI Research upon humans finds a connection with the caudalmost part of parahippocampus and superior temporal gyrus. No connections with the inferior parietal lobule, prefrontal cortex nor primary motor cortex.

Cognitive/Associative Central Region

This occurs around the precuneal sulcus (  green in figure) and is connected with the inferior parietal lobule particularly the angular gyrus and prefrontal areas 10, 46 and 8. No connections exist with premotor, motor, or somatosensory areas. The areas with which it links are involved in executive functions, working memory and motor planning.

Visual Posterior Region

This occurs along the parieto-occipital fissure (  yellow in figure). This connects with visual areas in the cuneus and primary visual cortex.

Below the cerebral cortex, the precuneus is connected with the dorsalmost nuclei of the thalamus, including the ventral lateral nucleus, the central and anterior nuclei of the intralaminar nuclear group, and the lateral pulvinar. Other connections include the claustrum, the dorsolateral caudate nucleus, putamen, and the zona incerta.[1][3] It also has links with the brainstem areas such as the pretectal area, the superior colliculus, the nucleus reticularis tegmenti pontis, and the basis pontis.[1][3]

Functional imaging has linked the precuneus to the processes involved in self-consciousness, such as reflective self-awareness, that involve rating one's own personality traits compared to those judged of other people.[9][10]

The precuneus is involved in memory tasks, such as when people look at images and try to respond based on what they have remembered in regard to verbal questions about their spatial details.[11] It is involved with the left prefrontal cortex in the recall of episodic memories[12][13] including past episodes related to the self.[10] The precuneus is also involved in source memory (in which the "source" circumstances of a memory are recalled) with the left inferior prefrontal cortex: here its role is postulated to be providing rich episodic contextual associations used by the prefrontal cortex to select the correct past memory.[14] In the recollection of memories, it has been postulated that the precuneus discerns whether contextual information exists that can be useful for involving the aid of the hippocampus. Alternatively it has a different involvement when judging the familiarity as it decides whether the processing of perceptual features would be more useful.[15] In this way the precuneus gets involved in diverse processes such as attention, episodic memory retrieval, working memory and conscious perception.[15]

The precuneus has been suggested to be involved in directing attention in space both when an individual makes movements and when imaging or preparing them.[1][16] It is involved in motor imagery and shifting attention between motor targets.[1] It is also involved in motor coordination that requires shifting attention to different spatial locations.[17] It is also together with the dorsal premotor cortex involved in visuospatial mental operations (such as in a modified form of the game of Amidakuji). It is suggested that while the premotor area engages in the mental operation, the precuneus aids monitoring the success of that operation in terms of internally represented visual images.[18]

The precuneus' role in mental imagery has been suggested to extend to that of modeling other people's views. It is activated when a person takes a third-person versus first-person visual point of view.[19] Together with the superior frontal gyrus and orbitofrontal cortex, the precuneus is activated when people make judgments that requires understanding whether to act out of empathy and forgiveness.[20]

Precuneus is thought to be related to response inhibition.[21]

It has been suggested that together with the posterior cingulate, the precuneus is "pivotal for conscious information processing".[22] The evidence for this link with consciousness comes from the effects of its disruption in epilepsy, brain lesions and vegetative state.[3][22] Also, cerebral glucose metabolism is at its highest in these two areas during wakefulness but is most reduced in them during anesthesia.[3][22] In addition, it is one of the areas of the brain most deactivated during slow-wave sleep and rapid eye movement sleep.[3]

Together with the prefrontal cortex, the precuneus, is more activated upon the learning of words briefly flashed when they are supraliminal (and so enter consciousness) than subliminal (and so do not enter consciousness).[23]

It has been suggested to be the 'core node' or 'hub' of the default mode network that is activated during "resting consciousness" in which people do not engage intentionally in sensory or motor activity.[3] This involvement in the default network is suggested to underlie its role in self-consciousness. However its involvement in the default network has been questioned.[2][24] Though one of the authors raising these doubts noted "our findings in this regard should be treated as preliminary."[2] A recent study showed that only ventral precuneus is involved in the default network.[25]

Olaf Sporns and Ed Bullmore have proposed that its functions link to its role as a central and well connected "small-world network" hub between parietal and prefrontal regions.

These clusters or modules are interlinked by specialized hub regions, ensuring that overall path lengths across the network are short. Most studies identified [such] hubs among parietal and prefrontal regions, providing a potential explanation for their well-documented activation by many cognitive functions. Particularly notable is the prominent structural role of the precuneus, a region that is homologous to the highly connected posteromedial cortex in the macaque. The precuneus is involved in self-referential processing, imagery and memory, and its deactivation is associated with anaesthetic-induced loss of consciousness. An intriguing hypothesis suggests that these functional aspects can be explained on the basis of its high centrality in the cortical network.[26]