Angular gyrus
| Angular gyrus | |
|---|---|
 | |
 Drawing of a cast to illustrate the relations of the brain to the skull. (Angular gyrus labeled at upper left, in yellow section.) | |
| Details | |
| Identifiers | |
| Latin | gyrus angularis |
| NeuroNames | 109 |
| NeuroLex ID | birnlex_1376 |
| TA98 | A14.1.09.124 |
| TA2 | 5472 |
| FMA | 61898 |
| Anatomical terms of neuroanatomy | |
The angular gyrus is a region of the brain in the parietal lobe, that lies near the superior edge of the temporal lobe, and immediately posterior to the supramarginal gyrus; it is involved in a number of processes related to language, mathematics and cognition. It is Brodmann area 39 of the human brain.
Function
Language
Geschwind proposed that written word is translated to internal monologue via the angular gyrus.[citation needed]
V. S. Ramachandran, and Edward Hubbard published a paper in 2003 in which they speculated that the angular gyrus is at least partially responsible for understanding metaphors. 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’.[1]
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 (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.[2] Sathian stated that “I don't think that there's only one area for metaphor processing...several recent lines of research indicate that engagement with abstract concepts is distributed around the brain.”[3] Vilayanur Ramachandran commented that“the authors have paved the way” to study how different brain regions communicate. “This is a very ingenious and elegant approach to the problem.”[4]
Mathematics and Spatial Cognition
Since 1919, brain injuries to the angular gyrus have been known to often cause arithmetic deficits.[5][6] Functional imaging has shown that while other parts of the parietal lobe bilaterally are involved in approximate calculations due to its link with spatiovisual abilities, the left angular gyrus together with left Inferior frontal gyrus are involved in exact calculation due to verbal arithmetic fact retrieval.[7] When activation in the left angular gyrus is greater, a person's arithmetic skills are also more competent.[8]
The right angular gyrus has been associated with spatiovisual attention toward salient features. [9] [10]It may allocate attention by employing a bottom-up strategy which draws on the area's ability to attend to retrieved memories. [9] For example, the angular gyrus plays a critical role in distinguishing left from right, by integrating conceptual understanding of the language term "left" or "right" with its location in space. [11]
Out-of-body experiences
Recent experiments have demonstrated the possibility that stimulation of the angular gyrus is the cause of out-of-body experiences.[12] Stimulation of the angular gyrus in one experiment caused a woman to perceive a phantom existence behind her.[13] 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.
Syndromes involving angular gyrus
Damage to the angular gyrus manifests as Gerstmann syndrome. Damage may impair one or more of the above functions.
Additional images
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Position of angular gyrus (shown in red). -
Lateral surface of left cerebral hemisphere, viewed from above. Angular gyrus is shown in orange. -
Lateral surface of left cerebral hemisphere, viewed from the side. Angular gyrus is shown in orange. -
Lateral view of a human brain, main gyri labeled.
References
- ^ Ramachandran, V.S., Hubbard, E.M, The Phenomenology of Synaesthesia, Journal of Consciousness Studies,10,No. 8,2003,pp. 49-57[1]
- ^ Metaphorically feeling:Comprehending textual metaphros actives somatosensory cortex, Simon,K, Stilla,R, Sathian,K, Brain and Language, December 2011, ScienceDirect web site [2]
- ^ Metaphorically Feeling:Warren, Tracy, Bioscience-Writer.com[3]
- ^ Metaphorically Feeling:Warren, Tracy, Bioscience-Writer.com[4]
- ^ Henschen SL. (1919) On language, music and calculation mechanisms and their localisation in the cerebrum. Zeitschrift fur die gesamte Neurologie und Psychiatrie 52:273–298.
- ^ Gerstmann J. (1940). Syndrome of finger agnosia, disorientation for right and left, agraphia and acalculia—Local diagnostic value. Arch Neurol Psychiatry 44:398–408.
- ^ Dehaene S, Spelke E, Pinel P, Stanescu R, Tsivkin S. (1999). Sources of mathematical thinking: behavioral and brain-imaging evidence. Science. 284(5416):970-4. doi:10.1126/science.284.5416.970 PMID 10320379
- ^ Grabner RH, Ansari D, Reishofer G, Stern E, Ebner F, Neuper C. (2007).Individual differences in mathematical competence predict parietal brain activation during mental calculation. Neuroimage. 38(2):346-56. PMID 17851092
- ^ a b Seghier M. L. (2012). The angular gyrus: multiple function ad multiple subdivisions. Neuroscientist (in press). PMID: 22547530
- ^ Arsalidou M, Taylor MJ. 2011. Is 2+2=4? Meta-analyses of brain areas needed for numbers and calculations. Neuroimage 54(3):2382–93. PMID: 20946958
- ^ Hirnstein M, Bayer U, Ellison A, Hausmann M. 2011. TMS over the left angular gyrus impairs the ability to discriminate left from right. Neuropsychologia 49(1):29–33. PMID: 21035475
- ^ Out-of-Body Experience? Your Brain Is to Blame - New York Times
- ^ Arzy, S., Seeck, M., Ortigue, S., Spinelli, L., Blanke, O., 2006. Induction of an illusory shadow person: Stimulation of a site on the brain's left hemisphere prompts the creepy feeling that somebody is close by. Nature, 443(21), pp.287.
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