Precuneus

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Precuneus
Medial surface of left cerebral hemisphere. (Precuneus visible at top left.) (Anterior to the right.)
Sagittal MRI slice with the precuneus shown in red. (Anterior to the left.)
Details
Identifiers
Latinpraecuneus
NeuroNames110
NeuroLex IDbirnlex_1446
TA98A14.1.09.223
TA25479
FMA61900
Anatomical terms of neuroanatomy

In

self, and aspects of consciousness
.

The location of the precuneus makes it difficult to study. Furthermore, it is rarely subject to isolated injury due to strokes, or trauma such as gunshot wounds. This has resulted in it being "one of the less accurately mapped areas of the whole cortical surface".[1] While originally described as homogeneous by Korbinian Brodmann, it is now appreciated to contain three subdivisions.[2]

It is also known after Achille-Louis Foville as the quadrate lobule of Foville.[1][3][4] The Latin form of praecuneus was first used in 1868 and the English precuneus in 1879.[5]

Structure

posterior cingulate
and its connections.)

The precuneus is located on the inside between the two

posterior cingulate area. Brodmann mapped it as the medial continuation of lateral parietal area 7
.

fMRI upon resting-state functional connectivity to also exist in humans (parallel fMRI research has also been done upon monkeys).[2]

Subdivisions

Sensorimotor Anterior Region

This occurs around the margin of the

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

primary visual cortex
.

Subcortical connections

Below the cerebral cortex, the precuneus is connected with the dorsalmost nuclei of the

basis pontis.[1][3]

Function

The

visuospatial
imagery. (It is not though clear how these—and the functions noted below—link with the above three subdivisions.)

The precuneus plays a role in itch sensations (there are many different types of itch) and their brain processing [7] “‘We can’t [yet] pinpoint what the precuneus does in itch, but it’s uniquely activated with itch and not pain.’” [8]

Self

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]

Electrical stimulation of the anterior portion can induce an

out of body experience.[11]

Memory

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.

episodic memories[13][14] 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.[15] 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.[citation needed] Alternatively it has a different involvement when judging the familiarity as it decides whether the processing of perceptual features would be more useful.[16] In this way the precuneus gets involved in diverse processes such as attention, episodic memory retrieval, working memory and conscious perception.[16]

Visuospatial

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.

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.[19]

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.[20] 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.[21]

Executive functions

Precuneus is thought to be related to response inhibition.[22]

Consciousness

It has been suggested that together with the posterior cingulate, the precuneus is "pivotal for conscious information processing".[23] The evidence for this link with consciousness comes from the effects of its disruption in epilepsy, brain lesions and vegetative state.[3][23] Also, cerebral glucose metabolism is at its highest in these two areas during wakefulness but is most reduced in them during anesthesia.[3][23] 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).[24]

Default network

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][25] Though one of the authors raising these doubts noted "our findings in this regard should be treated as preliminary."[2] A later study in 2012 showed that only ventral precuneus is involved in the default network.[26]

Parietal prefrontal central hub

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.[27]

Correlation of grey matter volume and subjective happiness score

A positive relationship has been found between the volume of grey matter in the right precuneus and the subject's subjective happiness score.[28]

Impact of mindfulness

A 6-week mindfulness based intervention was found to correlate with a significant grey matter increase within the precuneus.[29]

Other animals

The precuneus seems to be a recently expanded part of the brain, as in less developed

New world monkeys "the superior parietal and precuneate regions are poorly developed".[1] It has been noted that "the precuneus is more highly developed (i.e. comprises a larger portion of the brain volume) in human beings than in non-human primates or other animals, has the most complex columnar cortical organization and is among the last regions to myelinate".[1]

Additional images

  • Precuneus of left cerebral hemisphere (shown in red).
    Precuneus of left cerebral hemisphere (shown in red).
  • Medial surface of left cerebral hemisphere. (Precuneus visible at top left.)
    Medial surface of left cerebral hemisphere. (Precuneus visible at top left.)
  • Medial surface of left cerebral hemisphere. (Precuneus colored in red.)
    Medial surface of left cerebral hemisphere. (Precuneus colored in red.)
  • Boundaries of precuneus are defined by the three sulci. (shown in red) marginal branch of the cingulate sulcus parieto-occipital sulcus subparietal sulcus The area colored blue represents parietal lobe.
    Boundaries of precuneus are defined by the three sulci. (shown in red) The area colored blue represents parietal lobe.
  • Human brain dissection video (1 min). Demonstrating the location of precuneus. ("SPL" in the video, means Superior parietal lobule)
  • Precuneus of right cerebral hemisphere.
    Precuneus of right cerebral hemisphere.
  • Precuneus highlighted in green on coronal T1 MRI images
    Precuneus highlighted in green on coronal T1 MRI images
  • Precuneus highlighted in green on sagittal T1 MRI images
    Precuneus highlighted in green on sagittal T1 MRI images
  • Precuneus highlighted in green on transversal T1 MRI images
    Precuneus highlighted in green on transversal T1 MRI images

References

  1. ^
    PMID 16399806
    .
  2. ^
    PMID 19903877
    .
  3. ^
    S2CID 8068770
    .
  4. ^ Foville AL. (1844). Traité complêt de l’anatomie, de la physiologie et de la pathologie du système nerveux cérébro-spinal. Paris, France: Fortin, Masson
  5. ^ Oxford English Dictionary, Precuneus.
  6. S2CID 20334615
    .
  7. S2CID 42208021
    .
  8. ^ Sutherland, S. 2016. When pain feels good. New Scientist 232(3101):37-38
  9. S2CID 23923373
    .
  10. ^
    PMID 15096584
    .
  11. ^ Jon Hamilton (August 4, 2023). "This sausage-shaped part of your brain causes out-of-body experiences". Short Wave. NPR.
  12. S2CID 10439632
    .
  13. S2CID 5953246
    .
  14. S2CID 24359894
    .
  15. S2CID 8173843
    .
  16. ^
    PMID 1989556
    .
  17. PMID 7620288
    .
  18. S2CID 25754084
    .
  19. S2CID 17788847
    .
  20. S2CID 17578549
    .
  21. S2CID 34437619
    .
  22. doi:10.15405/epsbs.2018.11.02.43
    .
  23. ^
    PMID 16186025
    .
  24. S2CID 39449352
    .
  25. S2CID 3167595
    .
  26. PMID 22116037
    .
  27. S2CID 205504722
    .
  28. PMID 26586449
    .
  29. PMID 25632405
    .

External links

Wikimedia Commons has media related to Precuneus.
  • Atlas image: n1a2p12 at the University of Michigan Health System - "Cerebral Hemisphere, Medial View"
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