The angular gyrus is a region of the

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

lying mainly in the posteroinferior region of the

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 ...

, occupying the posterior part of 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 neurolo ...

. It represents the

Brodmann area A Brodmann area is a region of the cerebral cortex, in the human or other primate brain, defined by its cytoarchitecture, or histological structure and organization of cells. History Brodmann areas were originally defined and numbered by th ...

39. Its significance is in transferring visual information to

Wernicke's area Wernicke's area (; ), also called Wernicke's speech area, is one of the two parts of the cerebral cortex that are linked to speech, the other being Broca's area. It is involved in the comprehension of written and spoken language, in contrast to B ...

, in order to make meaning out of visually perceived words. It is also involved in a number of processes related to language, number processing and spatial cognition, memory retrieval,

attention Attention is the behavioral and cognitive process of selectively concentrating on a discrete aspect of information, whether considered subjective or objective, while ignoring other perceivable information. William James (1890) wrote that "Atte ...

, and

theory of mind In psychology, theory of mind refers to the capacity to understand other people by ascribing mental states to them (that is, surmising what is happening in their mind). This includes the knowledge that others' mental states may be different fro ...

Anatomy

Connections

Left and right angular

gyri In neuroanatomy, a gyrus (pl. gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci (depressions or furrows; sg. ''sulcus''). Gyri and sulci create the folded appearance of the brain in humans and other ma ...

are connected by the dorsal splenium and isthmus of the

corpus callosum The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental mam ...

Boundaries

* Anteriorly by the

Supramarginal gyrus The supramarginal gyrus is a portion of the parietal lobe. This area of the brain is also known as Brodmann area 40 based on the brain map created by Korbinian Brodmann to define the structures in the cerebral cortex. It is probably involved wit ...

. * Superiorly by the

Intraparietal sulcus The intraparietal sulcus (IPS) is located on the lateral surface of the parietal lobe, and consists of an oblique and a horizontal portion. The IPS contains a series of functionally distinct subregions that have been intensively investigated usin ...

. * Posteriorly 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 ...

. * Inferiorly the angular gyrus of the parietal lobe is continuous as the superior and

middle temporal gyri Middle temporal gyrus is a gyrus in the brain on the temporal lobe. It is located between the superior temporal gyrus and inferior temporal gyrus. It corresponds largely to Brodmann area 21. The middle temporal gyrus is bounded by: * the super ...

. Also, the angular sulcus, which is capped by the angular gyrus, is continuous as the

superior temporal sulcus The superior temporal sulcus (STS) is the sulcus separating the superior temporal gyrus from the middle temporal gyrus in the temporal lobe of the brain. A sulcus (plural sulci) is a deep groove that curves into the largest part of the brain, ...

inferiorly.

Function

The angular gyrus is the part of the brain associated with complex language functions (i.e. reading, writing and interpretation of what is written). Lesion to this part of the brain shows symptoms of the

Gerstmann syndrome Gerstmann syndrome is a neuropsychological disorder that is characterized by a constellation of symptoms that suggests the presence of a lesion usually near the junction of the temporal and parietal lobes at or near the angular gyrus. Gerstmann ...

: effects include finger agnosia, alexia (inability to read), acalculia (inability to use arithmetic operations), agraphia (inability to copy), and left-right confusion.

Language

Geschwind proposed that written word is translated to internal monologue via the angular gyrus.

V. S. Ramachandran Vilayanur Subramanian Ramachandran (born 10 August 1951) is an Indian-American neuroscientist. He is known for his wide-ranging experiments and theories in behavioral neurology, including the invention of the mirror box. Ramachandran is a disti ...

, and Edward Hubbard published a paper in 2003 in which they speculated that the angular gyrus is at least partially responsible for understanding

metaphor A metaphor is a figure of speech that, for rhetorical effect, directly refers to one thing by mentioning another. It may provide (or obscure) clarity or identify hidden similarities between two different ideas. Metaphors are often compared wit ...

s. They stated:

There may be neurological disorders that disturb metaphor and synaesthesia. This has not been studied in detail but we have seen disturbances in the Bouba/Kiki effect (Ramachandran & Hubbard, 2001a) as well as with proverbs in patients with angular gyrus lesions. It would be interesting to see whether they have deficits in other types of synaesthetic metaphor, e.g. 'sharp cheese' or 'loud shirt'. There are also hints that patients with right hemisphere lesions show problems with metaphor. It is possible that their deficits are mainly with spatial metaphors, such as 'He stepped down as director'.

The fact that the angular gyrus is proportionately much larger in hominids than other primates, and its strategic location at the crossroads of areas specialized for processing touch, hearing and vision, leads Ramachandran to believe that it is critical both to conceptual metaphors and to cross-modal abstractions more generally. However, recent research challenges this theory. Research by Krish Sathian (Emory University) using

functional magnetic resonance imaging 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 o ...

(fMRI) suggests that the angular gyrus does not play a role in creating conceptual metaphors. Sathian theorizes that conceptual metaphors activate the texture-selective somatosensory cortex in the parietal operculum. Brownsett and Wise highlight the role of the left angular gyrus in both speaking and writing.

Arithmetic and spatial cognition

Since 1919,

brain injuries 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 t ...

to the angular gyrus have been known to often cause

arithmetic Arithmetic () is an elementary part of mathematics that consists of the study of the properties of the traditional operations on numbers— addition, subtraction, multiplication, division, exponentiation, and extraction of roots. In the 19th ...

deficits.

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 shown that while other parts of the

bilaterally are involved in approximate calculations due to its link with spatiovisual abilities, the left angular gyrus together with left

Inferior frontal gyrus The inferior frontal gyrus (IFG), (gyrus frontalis inferior), is the lowest positioned gyrus of the frontal gyri, of the frontal lobe, and is part of the prefrontal cortex. Its superior border is the inferior frontal sulcus (which divides it f ...

are involved in exact calculation due to verbal arithmetic fact retrieval. When activation in the left angular gyrus is greater, a person's arithmetic skills are also more competent.

Attention

The right angular gyrus has been associated with spatiovisual attention toward salient features. It may allocate attention by employing a bottom-up strategy which draws on the area's ability to attend to retrieved memories. For example, the angular gyrus plays a critical role in distinguishing left from right by integrating the conceptual understanding of the language term "left" or "right" with its location in space. Furthermore, the angular gyrus has been associated with orienting in three dimensional space, not because it interprets space, but because it may control attention shifts in space.

Other functions

Default mode network

The angular gyrus is part 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 prefro ...

, a network of brain regions activated during multi-modal activities that are independent of external stimuli.

Awareness

The angular gyrus reacts differently to intended and consequential movement. This suggests that the angular gyrus monitors the self's intended movements and uses the added information to compute differently, as it does for consequential movements. By recording the discrepancy, the angular gyrus maintains an awareness of the self.

Memory retrieval

Activation of the angular gyrus shows that not only does it mediate memory retrieval, but it also notes contradictions between what is expected from the retrieval, and what is unusual. The angular gyrus can access both content and episodic memories and is useful in inferring from these the intentions of human characters. Furthermore, the angular gyrus may use a feedback strategy to ascertain whether a retrieval is expected or unusual.

Out-of-body experiences

Experiments have demonstrated the ability of stimulation of the right angular gyrus to induce

out-of-body experiences An out-of-body experience (OBE or sometimes OOBE) is a phenomenon in which a person perceives the world from a location outside their physical body. An OBE is a form of autoscopy (literally "seeing self"), although this term is more commonly us ...

. Stimulation of the left angular gyrus in one experiment caused a woman to perceive a shadowy person lurking behind her. The shadowy figure is actually a perceived double of the self. Another such experiment gave the test subject the sensation of being on the ceiling. This is attributed to a discrepancy in the actual position of the body, and the mind's perceived location of the body.

Clinical significance

Damage to the angular gyrus manifests as

. Damage may impair one or more of the below functions. # Dysgraphia/agraphia: deficiency in the ability to write #

Dyscalculia Dyscalculia () is a disability resulting in difficulty learning or comprehending arithmetic, such as difficulty in understanding numbers, learning how to manipulate numbers, performing mathematical calculations, and learning facts in mathematics. ...

/acalculia: difficulty in learning or comprehending mathematics #

Finger agnosia Finger agnosia, first defined in 1924 by Josef Gerstmann, is the loss in the ability to distinguish, name, or recognize the fingers—not only the patient's own fingers, but also the fingers of others, and drawings and other representations of fing ...

: inability to distinguish the fingers on the hand # Left-right disorientation

Additional images

File:Angular gyrus animation small.gif, Position of angular gyrus (shown in red). File:Gray725 angular gyrus.png, Lateral surface of left cerebral hemisphere, viewed from above. Angular gyrus is shown in orange. File:Gray726 angular gyrus.png, Lateral surface of left cerebral hemisphere, viewed from the side. Angular gyrus is shown in orange. Image:Gehirn, lateral - Hauptgyri beschriftet.svg, Lateral view of a human brain, main gyri labeled. File:Slide3HAN.JPG, Cerebrum. Lateral view.Deep dissection. File:Slide4HAN.JPG, Cerebrum. Lateral view.Deep dissection. File:Angular gyrus coronal sections.gif, Angular gyrus highlighted in green on coronal T1 MRI image File:Angular gyrus sagittal sections.gif, Angular gyrus highlighted in green on sagittal T1 MRI image File:Angular gyrus transversal sections.gif, Angular gyrus highlighted in green on transversal T1 MRI image

References

External links

NIF Search - Angular Gyrus
via the

Neuroscience Information Framework The Neuroscience Information Framework is a repository of global neuroscience web resources, including experimental, clinical, and translational neuroscience databases, knowledge bases, atlases, and genetic/ genomic resources and provides many aut ...

{{Authority control Gyri Parietal lobe