neuroanatomy Neuroanatomy is the study of the structure and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defi ...

, the precuneus is the portion of the

superior parietal lobule The superior parietal lobule is bounded in front by the upper part of the postcentral sulcus, but is usually connected with the postcentral gyrus above the end of the sulcus. The superior parietal lobule contains Brodmann's areas 5 and 7. Beh ...

on the medial surface of each brain

hemisphere Hemisphere refers to: * A half of a sphere As half of the Earth * A hemisphere of Earth ** Northern Hemisphere ** Southern Hemisphere ** Eastern Hemisphere ** Western Hemisphere ** Land and water hemispheres * A half of the (geocentric) celes ...

. It is located in front of the

cuneus The cuneus (; plural cunei) is a smaller lobe in the occipital lobe of the brain. The cuneus is bounded anteriorly by the parieto-occipital sulcus and inferiorly by the calcarine sulcus. Function The cuneus (Brodmann area 17) receives visu ...

(the upper portion of the

occipital lobe The occipital lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The name derives from its position at the back of the head, from the Latin ''ob'', "behind", and ''caput'', "head". The occipital lobe is the vi ...

). The precuneus is bounded in front by the marginal branch of the

cingulate sulcus The cingulate sulcus is a sulcus (brain fold) on the cingulate cortex in the medial wall of the cerebral cortex. The frontal and parietal lobes are separated from the cingulate gyrus by the cingulate sulcus. It terminates as the marginal sulcus o ...

, at the rear by the

parieto-occipital sulcus In neuroanatomy, the parieto-occipital sulcus (also called the parieto-occipital fissure) is a deep sulcus in the cerebral cortex that marks the boundary between the cuneus and precuneus, and also between the parietal and occipital lobes. Only ...

, and underneath by the

subparietal sulcus In neuroanatomy, the subparietal sulcus () or suprasplenial sulcus is a sulcus, or crevice, on the medial surface of each cerebral hemisphere, above the splenium of the corpus callosum. It separates the precuneus from the posterior part of th ...

. It is involved with

episodic memory Episodic memory is the memory of everyday events (such as times, location geography, associated emotions, and other contextual information) that can be explicitly stated or conjured. It is the collection of past personal experiences that occurred ...

, visuospatial processing, reflections upon

self The self is an individual as the object of that individual’s own reflective consciousness. Since the ''self'' is a reference by a subject to the same subject, this reference is necessarily subjective. The sense of having a self—or ''selfhoo ...

, and aspects of

consciousness Consciousness, at its simplest, is sentience and awareness of internal and external existence. However, the lack of definitions has led to millennia of analyses, explanations and debates by philosophers, theologians, linguisticians, and scien ...

. The location of the precuneus makes it difficult to study. Furthermore, it is rarely subject to isolated injury due to

stroke A stroke is a disease, medical condition in which poor cerebral circulation, blood flow to the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemorr ...

s, or trauma such as gunshot wounds. This has resulted in it being "one of the less accurately mapped areas of the whole cortical surface". While originally described as homogeneous by

Korbinian Brodmann Korbinian Brodmann (17 November 1868 – 22 August 1918) was a German neurologist who became famous for mapping the cerebral cortex and defining 52 distinct regions, known as Brodmann areas, based on their cytoarchitectonic (histological) char ...

, it is now appreciated to contain three subdivisions. It is also known after

Achille-Louis Foville Achille-Louis Foville (6 August 1799 – 22 June 1878) was a French people, French Neurology, neurologist and Psychiatry, psychiatrist. He produced the first description of the terminal stria. Life Foville was born in Pontoise, France and rec ...

as the ''quadrate lobule of Foville''. The Latin form of was first used in 1868 and the English ''precuneus'' in 1879.

Structure

The precuneus is located on the inside between the two

cerebral hemisphere The vertebrate cerebrum ( brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemisphere ...

s in the rear region between the

somatosensory cortex In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch ( haptic perception), as well as temperature (thermoception), body position (proprioception), and pain. It i ...

and forward of the

(which contains the

visual cortex The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus ...

). It is above the

posterior cingulate The posterior cingulate cortex (PCC) is the caudal part of the cingulate cortex, located posterior to the anterior cingulate cortex. This is the upper part of the " limbic lobe". The cingulate cortex is made up of an area around the midline of th ...

. Following

it has traditionally been considered a homogeneous structure and with limited distinction between it and the neighboring

area. Brodmann mapped it as the medial continuation of lateral parietal area 7. Axon tracing research on

macaque monkey The macaques () constitute a genus (''Macaca'') of gregarious Old World monkeys of the subfamily Cercopithecinae. The 23 species of macaques inhabit ranges throughout Asia, North Africa, and (in one instance) Gibraltar. Macaques are principall ...

s has established that it consists of three subdivisions which now have been confirmed by

fMRI Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area ...

upon resting-state functional connectivity to also exist in

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...

s (parallel fMRI research has also been done upon monkeys).

Subdivisions

;Sensorimotor Anterior Region This occurs around the margin of the

(blue in figure) and is connected with sensorimotor areas of the cerebral cortex such as the

paracentral lobule In neuroanatomy, the paracentral lobule is on the medial surface of the cerebral hemisphere and is the continuation of the precentral and postcentral gyri. The paracentral lobule controls motor and sensory innervations of the contralateral low ...

supplementary motor area The supplementary motor area (SMA) is a part of the motor cortex of primates that contributes to the control of movement. It is located on the midline surface of the hemisphere just in front of (anterior to) the primary motor cortex leg representa ...

premotor cortex The premotor cortex is an area of the motor cortex lying within the frontal lobe of the brain just anterior to the primary motor cortex. It occupies part of Brodmann's area 6. It has been studied mainly in primates, including monkeys and humans ...

somatosensory area In neuroanatomy, the postcentral gyrus is a prominent gyrus in the lateral parietal lobe of the human brain. It is the location of the primary somatosensory cortex, the main sensory receptive area for the somatosensory system, sense of touch. Lik ...

(

Brodmann area 2 In neuroanatomy, the postcentral gyrus is a prominent gyrus in the lateral parietal lobe of the human brain. It is the location of the primary somatosensory cortex, the main sensory receptive area for the sense of touch. Like other sensory areas, ...

), parietal operculum and insula. fMRI Research upon humans finds a connection with the caudalmost part of

parahippocampus The parahippocampal gyrus (or hippocampal gyrus') is a grey matter cortical region of the brain that surrounds the hippocampus and is part of the limbic system. The region plays an important role in memory encoding and retrieval. It has been inv ...

and

superior temporal gyrus The superior temporal gyrus (STG) is one of three (sometimes two) gyri in the temporal lobe of the human brain, which is located laterally to the head, situated somewhat above the external ear. The superior temporal gyrus is bounded by: * the l ...

. No connections with the

inferior parietal lobule The inferior parietal lobule (subparietal district) lies below the horizontal portion of the intraparietal sulcus, and behind the lower part of the postcentral sulcus. Also known as Geschwind's territory after Norman Geschwind, an American neur ...

prefrontal cortex In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, BA13, BA14, BA24, BA25, BA32, BA44, BA45, BA ...

nor

primary motor cortex The primary motor cortex (Brodmann area 4) is a Human brain, brain region that in humans is located in the dorsal portion of the frontal lobe. It is the primary cortex, primary region of the motor system and works in association with other motor ...

. ;Cognitive/Associative Central Region This occurs around the precuneal sulcus (green in figure) and is connected with the

particularly the

angular gyrus The angular gyrus is a region of the brain lying mainly in the posteroinferior region of the parietal lobe, occupying the posterior part of the inferior parietal lobule. It represents the Brodmann area 39. Its significance is in transferring ...

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 In cognitive science and neuropsychology, executive functions (collectively referred to as executive function and cognitive control) are a set of cognitive processes that are necessary for the cognitive control of behavior: selecting and su ...

working memory Working memory is a cognitive system with a limited capacity that can hold information temporarily. It is important for reasoning and the guidance of decision-making and behavior. Working memory is often used synonymously with short-term memory, ...

and

motor planning In psychology and neuroscience Neuroscience is the science, scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions and disorders. It is a Multidisciplinary approach, multidisciplinary scien ...

. ;Visual Posterior Region This occurs along the parieto-occipital fissure (yellow in figure). This connects with visual areas in the

and

primary visual cortex The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and ...

Subcortical connections

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

thalamus The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all direct ...

, including the

ventral lateral nucleus The ventral lateral nucleus (VL) is a nucleus in the ventral nuclear group of the thalamus. Inputs and outputs It receives neuronal inputs from the basal ganglia which includes the substantia nigra and the globus pallidus (via the thalamic fascic ...

, the central and anterior nuclei of the intralaminar nuclear group, and the lateral pulvinar. Other connections include the

claustrum The claustrum (Latin, meaning "to close" or "to shut") is a thin, bilateral collection of neurons and supporting glial cells, that connects to cortical (e.g., the pre-frontal cortex) and subcortical regions (e.g., the thalamus) of the brain. It ...

, the dorsolateral

caudate nucleus The caudate nucleus is one of the structures that make up the corpus striatum, which is a component of the basal ganglia in the human brain. While the caudate nucleus has long been associated with motor processes due to its role in Parkinson's d ...

putamen The putamen (; from Latin, meaning "nutshell") is a round structure located at the base of the forebrain (telencephalon). The putamen and caudate nucleus together form the dorsal striatum. It is also one of the structures that compose the basal ...

, and the

zona incerta The zona incerta (ZI) is a horizontally elongated region of gray matter in the subthalamus below the thalamus. Its connections project extensively over the brain from the cerebral cortex down into the spinal cord. Its function is unknown, though ...

. It also has links with the

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is ...

areas such as the

pretectal area In neuroanatomy, the pretectal area, or pretectum, is a midbrain structure composed of seven nuclei and comprises part of the subcortical visual system. Through reciprocal bilateral projections from the retina, it is involved primarily in mediati ...

, the

superior colliculus In neuroanatomy, the superior colliculus () is a structure lying on the roof of the mammalian midbrain. In non-mammalian vertebrates, the homologous structure is known as the optic tectum, or optic lobe. The adjective form '' tectal'' is common ...

, the nucleus reticularis tegmenti pontis, and the

basis pontis The basilar part of pons, also known as basis pontis, is the ventral part of the pons; the dorsal part is known as the pontine tegmentum. The basilar pons makes up two thirds of the pons within the brainstem. It has a ridged appearance with a shal ...

Function

The

mental imagery A mental image is an experience that, on most occasions, significantly resembles the experience of 'perceiving' some object, event, or scene, but occurs when the relevant object, event, or scene is not actually present to the senses. There are ...

concerning the

has been located in the forward part of the precuneus with posterior areas being involved with

. Another area has been linked to 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 “‘We can’t etpinpoint what the precuneus does in itch, but it’s uniquely activated with itch and not pain.’”

Self

Functional imaging Functional imaging (or physiological imaging) is a medical imaging technique of detecting or measuring changes in metabolism, blood flow, regional chemical composition, and absorption. As opposed to structural imaging, functional imaging center ...

has linked the precuneus to the processes involved in

self-consciousness Self-consciousness is a heightened sense of awareness of oneself. It is not to be confused with consciousness in the sense of qualia. Historically, "self-consciousness" was synonymous with "self-awareness", referring to a state of awareness that ...

, such as reflective self-awareness, that involve rating one's own personality traits compared to those judged of other people.

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. It is involved with the left prefrontal cortex in the recall of

episodic memories Episodic memory is the memory of everyday events (such as times, location geography, associated emotions, and other contextual information) that can be explicitly stated or conjured. It is the collection of past personal experiences that occurred ...

including past episodes related to the self. 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. 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 The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic syste ...

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

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. It is involved in motor imagery and shifting attention between motor targets. It is also involved in

motor coordination Motor coordination is the orchestrated movement of multiple body parts as required to accomplish intended actions, like walking. This coordination is achieved by adjusting kinematic and kinetic parameters associated with each body part involved in ...

that requires shifting attention to different spatial locations. It is also together with the dorsal

involved in visuospatial mental operations (such as in a modified form of the game of

Amidakuji Ghost Leg (), known in Japan as or in Korea as Sadaritagi (사다리타기, literally "ladder climbing"), is a method of lottery designed to create random pairings between two sets of any number of things, as long as the number of elements in eac ...

). 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. 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. Together with the

superior frontal gyrus In neuroanatomy, the superior frontal gyrus (SFG, also marginal gyrus) is a gyrus – a ridge on the brain's cerebral cortex – which makes up about one third of the frontal lobe. It is bounded laterally by the superior frontal sulcus. The su ...

and

orbitofrontal cortex The orbitofrontal cortex (OFC) is a prefrontal cortex region in the frontal lobes of the brain which is involved in the cognitive process of decision-making. In non-human primates it consists of the association cortex areas Brodmann area 11, 1 ...

, the precuneus is activated when people make judgments that requires understanding whether to act out of

empathy Empathy is the capacity to understand or feel what another person is experiencing from within their frame of reference, that is, the capacity to place oneself in another's position. Definitions of empathy encompass a broad range of social, co ...

and

forgiveness Forgiveness, in a psychological sense, is the intentional and voluntary process by which one who may initially feel victimized or wronged, goes through a change in feelings and attitude regarding a given offender, and overcomes the impact of t ...

Executive functions

Precuneus is thought to be related to response inhibition.

Consciousness

It has been suggested that together with the posterior cingulate, the precuneus is "pivotal for conscious information processing". The evidence for this link with

comes from the effects of its disruption in

epilepsy Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrica ...

brain lesion Neurotrauma, brain damage or brain injury (BI) is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors. In general, brain damage refers to significant, undiscriminating ...

s and

vegetative state A persistent vegetative state (PVS) or post-coma unresponsiveness (PCU) is a disorder of consciousness in which patients with severe brain damage are in a state of partial arousal rather than true awareness. After four weeks in a vegetative stat ...

. Also, cerebral glucose metabolism is at its highest in these two areas during

wakefulness Wakefulness is a daily recurring brain state and state of consciousness in which an individual is conscious and engages in coherent cognitive and behavioral responses to the external world. Being awake is the opposite of being asleep, in which m ...

but is most reduced in them during

anesthesia Anesthesia is a state of controlled, temporary loss of sensation or awareness that is induced for medical or veterinary purposes. It may include some or all of analgesia (relief from or prevention of pain), paralysis (muscle relaxation), ...

. In addition, it is one of the areas of the brain most deactivated during slow-wave sleep and

rapid eye movement sleep Rapid eye movement sleep (REM sleep or REMS) is a unique phase of sleep in mammals and birds, characterized by random rapid movement of the eyes, accompanied by low muscle tone throughout the body, and the propensity of the sleeper to dream ...

. 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 Subliminal may refer to: * Subliminal stimuli, sensory stimuli below an individual's threshold for conscious perception * Subliminal channel, in cryptography, a covert channel that can be used over an insecure channel * Subliminal (rapper) (born ...

(and so do not enter consciousness).

Default network

It has been suggested to be the 'core node' or 'hub' of the

default mode network In neuroscience, the default mode network (DMN), also known as the default network, default state network, or anatomically the medial frontoparietal network (M-FPN), is a large-scale brain network primarily composed of the dorsal medial pref ...

that is activated during "resting consciousness" in which people do not engage intentionally in sensory or motor activity. This involvement in the default network is suggested to underlie its role in

. However its involvement in the default network has been questioned. Though one of the authors raising these doubts noted "our findings in this regard should be treated as preliminary." A recent study showed that only ventral precuneus is involved in the default network.

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 A small-world network is a type of mathematical graph in which most nodes are not neighbors of one another, but the neighbors of any given node are likely to be neighbors of each other and most nodes can be reached from every other node by a sm ...

" 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
uch Uch ( pa, ; ur, ), frequently referred to as Uch Sharīf ( pa, ; ur, ; ''"Noble Uch"''), is a historic city in the southern part of Pakistan's Punjab province. Uch may have been founded as Alexandria on the Indus, a town founded by Alexan ...
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.

Correlation of grey matter volume and subjective happiness score

A positive relationship has been found between the volume of

grey matter Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil ( dendrites and unmyelinated axons), glial cells ( astrocytes and oligodendrocytes), synapses, and capillaries. Grey matter is ...

in the right precuneus and the subject's subjective happiness score.

Impact of mindfulness

A 6-week

mindfulness Mindfulness is the practice of purposely bringing one's attention to the present-moment experience without evaluation, a skill one develops through meditation or other training. Mindfulness derives from ''sati'', a significant element of Hind ...

based intervention was found to correlate with a significant

increase within the precuneus.

Other animals

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

primate Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians ( monkeys and apes, the latter includin ...

s such as

New world monkey New World monkeys are the five families of primates that are found in the tropical regions of Mexico, Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Ceboidea ...

s "the superior parietal and precuneate regions are poorly developed". 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".

Additional images

File:Precuneus animation.gif, Precuneus of left cerebral hemisphere (shown in red). File:Cerebral Gyri - Medial Surface1.png, Medial surface of left cerebral hemisphere. (Precuneus visible at top left.) File:Human brain inferior-medial view with marked Precuneus.JPG, Medial surface of left cerebral hemisphere. (Precuneus colored in red.) File:ParietCapts medial.png, Boundaries of precuneus are defined by the three sulci. (shown in red) The area colored blue represents

parietal lobe The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus. The parietal lobe integrates sensory informa ...

. File:Cerebral Hemisphere Demonstration - Sanjoy Sanyal - Neuroscience Lab Fall 2013 (Cropped from 30m22s to 31m22s) Precuneus.webm, Human brain dissection video (1 min). Demonstrating the location of precuneus. ("SPL" in the video, means

Superior parietal lobule The superior parietal lobule is bounded in front by the upper part of the postcentral sulcus, but is usually connected with the postcentral gyrus above the end of the sulcus. The superior parietal lobule contains Brodmann's areas 5 and 7. Beh ...

) File:Precuneus - DK ATLAS.png, Precuneus of right cerebral hemisphere. File:Precuneus coronal sections.gif, Precuneus highlighted in green on coronal T1 MRI images File:Precuneus sagittal sections.gif, Precuneus highlighted in green on sagittal T1 MRI images File:Precuneus transversal sections.gif, Precuneus highlighted in green on transversal T1 MRI images

References

External links

* - "Cerebral Hemisphere, Medial View" {{Authority control Parietal lobe Gyri Articles containing video clips Medial surface of cerebral hemisphere