Planum temporale

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Planum temporale
BrocasAreaSmall.png
Approximate location of Wernicke's area highlighted in gray
Identifiers
NeuroNames 2333
TA98 A14.1.09.143
TA2 5493
FMA 74564
Anatomical terms of neuroanatomy
Diagram labeling planum temporale in green. Face sup T1.png
Diagram labeling planum temporale in green.

The planum temporale is the cortical area just posterior to the auditory cortex (Heschl's gyrus) within the Sylvian fissure. [1] It is a triangular region which forms the heart of Wernicke's area, one of the most important functional areas for language. [2] Original studies on this area found that the planum temporale was one of the most asymmetric regions in the brain, with this area being up to ten times larger in the left cerebral hemisphere than the right. [3]

Contents

Location

The planum temporale makes up the superior surface of the superior temporal gyrus to the parietal lobe. [4] The posterior extent of the planum temporale has been variably defined, which has led to disputes to estimates of size and degree of asymmetry. [4]

Asymmetry

The planum temporale shows a significant asymmetry. In 65% of all individuals the left planum temporale appears to be more developed, while the right planum temporale is more developed in only 11%. In some people’s brains, the planum temporale is more than five times larger on the left than on the right, making it the most asymmetrical structure in the brain. Evidence for this asymmetry has also been seen in great apes. [5]

This greater size of the left planum temporale compared with the right is already present in the fetus, where it can be observed starting from the 31st week of gestation. This observation strengthens the hypothesis of a genetic predisposition for brain asymmetry, however the effect of fetal experience has not been ruled out. [2] [6] Leftward asymmetry, however, does not directly relate to asymmetry of language processing in all individuals. [4]

In addition, more and more research is suggesting that the apparent asymmetries in this region are the result of old techniques and criteria used to identify the planum temporale[ citation needed ]. When new imaging is used that takes into account asymmetries in the curvatures of lateral fissures, the hemispheric asymmetries of the planum temporale become negligible[ citation needed ]. This newer imaging would indicate that the size of the region would not explain the higher faculties of language in the left hemisphere, but would instead require an analysis of the neural circuitry. [7]

Gender based asymmetry

Imaging has repeatedly suggested gender marked differences in planum temporale surface area asymmetry. There have been multiple findings suggesting a greater leftward surface area asymmetry in male subjects, with no significant difference as mediated by gender of the right part of the planum temporale. [8]

Recent evidence can be used to support the idea that differences between males and females in planum temporale asymmetry begin to develop and show early in development, potentially during prenatal stages. Gender based asymmetry may be the result of environmental factors occurring in-utero, such as levels of testosterone. [9]

Certain studies have found differences within the planum temporale on a microscopic level, finding greater cell packing density in females, as well as a reduction of micro-structural asymmetry. Females have also been found to display asymmetry in grey matter volume. [9]

Due to the novel nature of these findings, researchers have yet to discern how to interpret these sex-based differences on brain function. [10]

Functions

The planum temporale is a highly lateralized brain structure involved with language and with music. Although the planum temporale is found to have an asymmetry in the normal population, having a leftward bias in right-handed individuals, people who possess absolute pitch have an increased leftward asymmetry of the planum temporale. This is due to a smaller than average volume of the right planum temporale and not a larger than average volume of the left. [11] The planum temporale may also play an important role in auditory processing with recent research suggesting that the region is responsible for representing the location of sounds in space. [12]

There have also been many studies that show the asymmetry of the planum temporale to be related to handedness of subjects. There have been reports of decreased asymmetry displayed on the left side of the planum temporale in those that are dominantly left handed. [10]

Atypical development

The planum temporale seems to be symmetrical in individuals with dyslexia, which may indicate that their low specialization in the left hemisphere is a cause of their disability. This symmetry also holds for people who stutter, although it is also possible to see a larger right planum temporale in stutters. It is thought that this bias for right hemisphere could be interrupting or impeding information flow between Wernickes and Broca's, which are on the left hemisphere.

MRI studies have shown that the planum temporale in schizophrenics is more symmetrical. [13] This reduced lateralization correlates with more severe positive symptoms, such as hallucinations, as measured by the PANSS. [13]

Sexual dimorphism has shown to play an important role on planum temporale studies within schizophrenia. These findings have highlighted the relevance and importance of sex/gender as a plays a key role on PT in schizophrenia, underlying the importance of gender as a key component of brain morphology and the specialized brain structure and function for schizophrenia. [14]

Non-human brains

Although the brain area was thought to be unique to humans, almost like the anatomic version of the linguistic "language organ" of Noam Chomsky, it was shown to be similarly leftward asymmetric in chimpanzees and other great apes but not other primates, [15] as was a related, rightward asymmetric, brain region the planum parietale that is implicated with dyslexia in humans. [16] Monkeys show cellular asymmetry but not gross anatomic asymmetry of the planum temporale. [17] (Brain Research, 2008). The question still remains open; what are great apes or monkeys using this "non-human primate language area" for? [18] [19] [20] [21]

Hemispheric differences

Summary Table
Left HemisphereRight Hemisphere
Normal development- larger in size and surface area [22] Normal development- smaller in size and surface area [22]
Decrease in size leads to difficulty with word recognition [22] -------
Damage can lead to impaired ability to decode phonemes [23] Damage can lead to impaired ability to decode phonemes [23]
Decrease in size can lead to dyslexia [23] Increase in size can lead to dyslexia [23]
Lesions result in difficulty of speech recognition [22] -------
-------Increased cortical thickness related to enhanced detection of visual motion in early deaf subjects [24]

Additional images

Related Research Articles

<span class="mw-page-title-main">Language center</span> Speech processing areas of the brain

In neuroscience and psychology, the term language center refers collectively to the areas of the brain which serve a particular function for speech processing and production. Language is a core system which gives humans the capacity to solve difficult problems, and provides them with a unique type of social interaction. Language allows individuals to attribute symbols to specific concepts, and utilize them through sentences and phrases that follow proper grammatical rules. Finally, speech is the mechanism by which language is orally expressed.

<span class="mw-page-title-main">Cerebral hemisphere</span> Left and right cerebral hemispheres of the brain

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 hemispheres has an outer layer of grey matter, the cerebral cortex, that is supported by an inner layer of white matter. In eutherian (placental) mammals, the hemispheres are linked by the corpus callosum, a very large bundle of nerve fibers. Smaller commissures, including the anterior commissure, the posterior commissure and the fornix, also join the hemispheres and these are also present in other vertebrates. These commissures transfer information between the two hemispheres to coordinate localized functions.

<span class="mw-page-title-main">Brodmann area 45</span> Brain area

Brodmann area 45 (BA45), is part of the frontal cortex in the human brain. It is situated on the lateral surface, inferior to BA9 and adjacent to BA46.

<span class="mw-page-title-main">Wernicke's area</span> Speech comprehension region in the dominant hemisphere of the hominid brain

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 Broca's area, which is primarily involved in the production of language. It is traditionally thought to reside in Brodmann area 22, which is located in the superior temporal gyrus in the dominant cerebral hemisphere, which is the left hemisphere in about 95% of right-handed individuals and 70% of left-handed individuals.

<span class="mw-page-title-main">Inferior frontal gyrus</span> Part of the brains prefrontal cortex

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.

<span class="mw-page-title-main">Longitudinal fissure</span> Deep groove separating the two cerebral hemispheres of the vertebrate brain

The longitudinal fissure is the deep groove that separates the two cerebral hemispheres of the vertebrate brain. Lying within it is a continuation of the dura mater called the falx cerebri. The inner surfaces of the two hemispheres are convoluted by gyri and sulci just as is the outer surface of the brain.

<span class="mw-page-title-main">Auditory cortex</span> Part of the temporal lobe of the brain

The auditory cortex is the part of the temporal lobe that processes auditory information in humans and many other vertebrates. It is a part of the auditory system, performing basic and higher functions in hearing, such as possible relations to language switching. It is located bilaterally, roughly at the upper sides of the temporal lobes – in humans, curving down and onto the medial surface, on the superior temporal plane, within the lateral sulcus and comprising parts of the transverse temporal gyri, and the superior temporal gyrus, including the planum polare and planum temporale.

<span class="mw-page-title-main">Transverse temporal gyrus</span> Gyrus of the primary auditory cortex of the brain

The transverse temporal gyri, also called Heschl's gyri or Heschl's convolutions, are gyri found in the area of primary auditory cortex buried within the lateral sulcus of the human brain, occupying Brodmann areas 41 and 42. Transverse temporal gyri are superior to and separated from the planum temporale by Heschl's sulcus. Transverse temporal gyri are found in varying numbers in both the right and left hemispheres of the brain and one study found that this number is not related to the hemisphere or dominance of hemisphere studied in subjects. Transverse temporal gyri can be viewed in the sagittal plane as either an omega shape or a heart shape.

<span class="mw-page-title-main">Superior temporal gyrus</span> One of three gyri of the temporal lobe of the brain

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

<span class="mw-page-title-main">Arcuate fasciculus</span> Neural pathway connecting Brocas area and Wernickes area

In neuroanatomy, the arcuate fasciculus is a bundle of axons that generally connects the Broca's area and the Wernicke's area in the brain. It is an association fiber tract connecting caudal temporal cortex and inferior frontal lobe.

<span class="mw-page-title-main">Angular gyrus</span> Gyrus of the parietal lobe of the brain

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.

<span class="mw-page-title-main">Language processing in the brain</span> How humans use words to communicate

In psycholinguistics, language processing refers to the way humans use words to communicate ideas and feelings, and how such communications are processed and understood. Language processing is considered to be a uniquely human ability that is not produced with the same grammatical understanding or systematicity in even human's closest primate relatives.

<span class="mw-page-title-main">Brodmann area 22</span>

Brodmann area 22 is a Brodmann's area that is cytoarchitecturally located in the posterior superior temporal gyrus of the brain. In the left cerebral hemisphere, it is one portion of Wernicke's area. The left hemisphere BA22 helps with generation and understanding of individual words. On the right side of the brain, BA22 helps to discriminate pitch and sound intensity, both of which are necessary to perceive melody and prosody. Wernicke's area is active in processing language and consists of the left Brodmann area 22 and Brodmann area 40, the supramarginal gyrus.

<span class="mw-page-title-main">Parahippocampal gyrus</span> Grey matter region surrounding the hippocampus

The parahippocampal 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 involved in some cases of hippocampal sclerosis. Asymmetry has been observed in schizophrenia.

<span class="mw-page-title-main">Lateralization of brain function</span> Specialization of some cognitive functions in one side of the brain

The lateralization of brain function is the tendency for some neural functions or cognitive processes to be specialized to one side of the brain or the other. The median longitudinal fissure separates the human brain into two distinct cerebral hemispheres, connected by the corpus callosum. Although the macrostructure of the two hemispheres appears to be almost identical, different composition of neuronal networks allows for specialized function that is different in each hemisphere.

<span class="mw-page-title-main">Inferior parietal lobule</span> Portion of the parietal lobe of the brain

The inferior parietal lobule 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 neurologist, who in the early 1960s recognised its importance. It is a part of the parietal lobe.

<span class="mw-page-title-main">Brain asymmetry</span> Term in human neuroanatomy referring to several things

In human neuroanatomy, brain asymmetry can refer to at least two quite distinct findings:

<span class="mw-page-title-main">Superior temporal sulcus</span> Part of the brains temporal lobe

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 is a deep groove that curves into the largest part of the brain, the cerebrum, and a gyrus is a ridge that curves outward of the cerebrum.

Emotional lateralization is the asymmetrical representation of emotional control and processing in the brain. There is evidence for the lateralization of other brain functions as well.

An estimated 90% of the world's human population consider themselves to be right-handed. The human brain's control of motor function is a mirror image in terms of connectivity; the left hemisphere controls the right hand and vice versa. This theoretically means that the hemisphere contralateral to the dominant hand tends to be more dominant than the ipsilateral hemisphere, however this is not always the case and there are numerous other factors which contribute in complex ways to physical hand preference.

References

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  2. 1 2 The Brain From Top To Bottom
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  6. ↑ Dorsaint-Pierre R, Penhune VB, Watkins KE, et al. (May 2006). "Asymmetries of the planum temporale and Heschl's gyrus: relationship to language lateralization". Brain. 129 (Pt 5): 1164–76. doi: 10.1093/brain/awl055 . PMID   16537567.
  7. ↑ Gazzaniga Michael S, Ivry Richard B, Mangun George R (2009). "Principles of Cerebral Organization". Cognitive Neuroscience: Biology of the Mind (3 ed.). New York, London: WW Norton and Company. p. 446.
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  10. 1 2 Good, Catriona D; Johnsrude, Ingrid; Ashburner, John; Henson, Richard N.A; Friston, Karl J; Frackowiak, Richard S.J (2001). "Cerebral Asymmetry and the Effects of Sex and Handedness on Brain Structure: A Voxel-Based Morphometric Analysis of 465 Normal Adult Human Brains". NeuroImage. 14 (3): 685–700. doi:10.1006/nimg.2001.0857. PMID   11506541. S2CID   16235256.
  11. ↑ Keenan, Julian Paul; Thangaraj, Ven; Halpern, Andrea R; Schlaug, Gottfried (2001). "Absolute Pitch and Planum Temporale". NeuroImage. 14 (6): 1402–8. doi:10.1006/nimg.2001.0925. PMID   11707095. S2CID   8886472.
  12. ↑ "Brain Center For 'Sound Space' Identified". Science Daily. 22 September 2007. Retrieved 22 September 2007.
  13. 1 2 Michael S. Ritsner (1 January 2009). The Handbook of Neuropsychiatric Biomarkers, Endophenotypes and Genes. Springer. pp. 101–. ISBN   978-1-4020-9831-4 . Retrieved 4 January 2013.
  14. ↑ Pigoni, A; Delvecchio, G; Perlini, C; Barillari, M; Ruggeri, M; Altamura, C; Bellani, M; Brambilla, P (2017). "Sexual-dimorphism of the planum temporale in schizophrenia: An MRI study". European Psychiatry. 41: S828. doi:10.1016/j.eurpsy.2017.01.1621. S2CID   149395883.
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  19. ↑ Chimps Like Us / We're Like Chimps
  20. ↑ Gibson, Kathleen Rita; Falk, Dean (2001). Evolutionary anatomy of the primate cerebral cortex. Cambridge, UK: Cambridge University Press. p. 216. ISBN   0-521-64271-X.
  21. ↑ Sciencenews 1998 PDF Archived 2011-05-24 at the Wayback Machine [ full citation needed ]
  22. 1 2 3 4 Binder J. R., Frost J. A., Hammeke T. A., Rao S. M., Cox R. W. (1996). Function of the left planum temporale in auditory and linguistic processing. Brain 119 1239–1247. 10.1093/brain/119.4.1239
  23. 1 2 3 4 Leonard, C. M., & Eckert, M. A. (2008). Asymmetry and Dyslexia. Developmental Neuropsychology, 33(6), 663–681. doi : 10.1080/87565640802418597
  24. ↑ Shiell, M. M., Champoux, F., & Zatorre, R. J. (2016). The Right Hemisphere Planum Temporale Supports Enhanced Visual Motion Detection Ability in Deaf People: Evidence from Cortical Thickness. Neural Plasticity, 2016, 7217630. doi : 10.1155/2016/7217630
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