Broca's area
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225487789
2008-07-13T23:21:11Z
213.93.218.244
/* Evolution of human languageWatson, Peter "Ideas: A History of Thought and Invention from Fire to Freud", Harper, New York 2006 [ISBN]0-06-093564-2], Chapter 2 */
{{Infobox Brain |
Name = Broca's area |
Latin = |
GraySubject = |
GrayPage = |
Image = BrocasAreaSmall.png |
Caption = Approximate location of Broca's area highlighted in gray |
Image2 = Inferior frontal gyrus.png |
Caption2 = Broca's area visible but not labeled. |
IsPartOf = [[Frontal lobe]]|
Components = |
Artery = [[Middle cerebral artery|Middle cerebral]]|
Vein = [[Superior sagittal sinus]]|
BrainInfoType = ancil |
BrainInfoNumber = 251 |
MeshName = |
MeshNumber = |
DorlandsPre = a_59 |
DorlandsSuf = 12150965 |
}}
'''Broca's area''' is a section of the human [[brain]] that is involved in [[language processing]], [[Speech communication|speech]] or [[Sign language|sign]]<ref>Horwitz B, Amunts K, Bhattacharyya R, Patkin D, Jeffries K, Zilles K, Braun AR. "Activation of Broca's area during the production of spoken and signed language: a combined cytoarchitectonic mapping and PET analysis," ''Neuropsychologia''. 2003; 41(14): 1868-76.</ref> production, and comprehension. Broca's area is named after the 19th-century physician [[Paul Broca]]. The concept of Broca's Area was originally produced with the intent to explain how speech production was inhibited in the learning of communication by the deaf; however, it is currently used to describe many anatomical aspects of psychological processing mechanisms.
==Description==
Broca's area is located in the [[pars opercularis|opercular]] and [[pars triangularis|triangular]] sections of the [[inferior frontal gyrus]] of the [[frontal lobe]] of the [[cerebral cortex|cortex]]. Broca's and [[Wernicke's area|Wernicke's]] areas are found unilaterally in the brain (dominant hemisphere, usually left hemisphere). It is supplied by the superior division of the Left Middle Cerebral Artery.
Broca's area comprises [[Brodmann area 44]]<ref>Mohr JP in ''Studies in Neurolinguistics'' (eds. Witaker H & Witaker NA) 201–235 (Academic, New York, 1976)</ref> and (according to some authorities) [[Brodmann area 45]].<ref>Penfield W & Roberts L ''Speech and Brain Mechanisms'' (Princeton Univ Press, Princeton, 1959)</ref><ref>{{cite journal | author=Ojemann GA, Ojemann JG, Lettich E, Berger MS | title=Cortical language localization in left, dominant hemisphere. An electical stimulation mapping investigation in 117 patients | year=1989 | journal=J Neurosurg | volume=71 | pages=316–26 | doi=10.1038/nature03628 }}</ref><ref>{{cite journal | author=Duffau H ''et al.'' | title=The role of dominant premotor cortex in language: a study uding intraoperative functional mapping in awake patients | year=2003 | journal=Neuroimage | volume=20 | pages=1903–14 | doi = 10.1016/S1053-8119(03)00203-9 <!--Retrieved from CrossRef by DOI bot-->}}</ref> Broca's Area is connected to [[Wernicke's area]] by a [[neural pathway]] called the [[arcuate fasciculus]]. The corresponding area in [[macaque]] monkeys is responsible for high-level control over orofacial actions.<ref>{{cite journal | author=Petrides M, Cadoret G, Mackey S | title=Orofacial somatomotor responses in the macaque monkey homologue of Broca's area | year=2005 | journal=Nature | volume=435 | pages=1235–38 | doi=10.1038/nature03628 }}</ref>
===Parts===
Broca's area has two main parts, which express different roles during language comprehension and production:
*''[[Pars triangularis]]'' (anterior), which is thought to support the interpretation of various 'modes' of [[stimulation|stimuli]] (plurimodal [[association (psychology)|association]]) and the programming of verbal conducts
*''[[Pars opercularis]]'' (posterior), which is thought to support the management of only one kind of stimulus (unimodal association) and the coordination of the speech organs for the actual production of language, given its favorable position close to motor-related areas
==Aphasia==
People suffering from damage to this area may show a condition called ''[[Broca's aphasia]]'' (sometimes known as ''[[expressive aphasia]]'', ''motor aphasia'', or ''nonfluent aphasia''), which makes them unable to create grammatically-complex sentences: It's often described as [[telegraphic speech]] and contains little but content words. Patients are usually aware that they cannot speak properly. Comprehension in Broca's aphasia is relatively normal, although many studies have demonstrated that Broca's aphasics have trouble understanding certain kinds of syntactically-complex sentences.<ref>{{cite journal | author=Caramazza A & Zurif E | title=Dissociation of algorithmic and heuristic processes in language comprehension: evidence from aphasia | year=1976 | journal=Brain and Language | volume=3 | pages=572–82 | doi = 10.1016/0093-934X(76)90048-1 <!--Retrieved from CrossRef by DOI bot-->}}</ref>
For example, in the following passage, a Broca's aphasic patient is trying to explain how he came to the hospital for dental surgery:
<blockquote>"Yes... ah... Monday... er... Dad and Peter H... (his own name), and Dad.... er... hospital... and ah... Wednesday... Wednesday, nine o'clock... and oh... Thursday... ten o'clock, ah doctors... two... an' doctors... and er... teeth... yah."<ref>Goodglass H & Geschwind N. Language disorders. In E. Carterette and M.P. Friedman (eds.) ''Handbook of Perception: Language and Speech. Vol II'' (New York, Academic Press, 1976)</ref></blockquote>
This type of aphasia can be contrasted with [[Wernicke's aphasia]], named for [[Carl Wernicke]], which is characterized by damage to more posterior regions of the left hemisphere in the superior [[temporal lobe]]. Wernicke's aphasia manifests as a more pronounced impairment in comprehension. Thus, while speech production retains a natural-sounding rhythm, and remains relatively normal grammatically, it is nonetheless often roundabout, vague, or meaningless. It is therefore also known as [[receptive aphasia]].
[[Positron emission tomography]] (PET) and [[functional magnetic resonance imaging]] (fMRI) have found decreases in activity in the Broca's area in [[stuttering]]. There is greater activation of the right hemisphere homologue of the Broca's area (area of Ross), which is believed to be a compensatory response to the hypoactivity in the Broca's area proper. [[Volumetric magnetic resonance imaging]] (VMRI) has shown that the ''[[pars triangularis]]'' is smaller in people that stutter.
==Evolution of human language<ref>Watson, Peter "Ideas: A History of Thought and Invention from Fire to Freud", Harper, New York 2006 [ISBN]0-06-093564-2], Chapter 2</ref>==
Broca's area is considered a marker for the development of language in the evolution of humans. The paleontological record of species leading to modern humans, ''[[Homo sapiens]]'', finds that this part of the neural structure of the brain is present in fossils of ''Homo sapiens'', and of ''[[Homo habilis]]'', whereas the presumed precursors of these early humanoids, ''[[Australopithecus|australopithecines]]'', lacked this area of the brain (note that this information depends on the analysis of skulls where the presence of Broca's area can be determined).
Whereas Broca's area is unique in its linguistic role to humans, it is present in animals, although it performs other similar roles that were adapted to language in humans.
The fossil record cannot, of course, give firm data about the beginning of language, which is one of the critical factors contributing to the evolution of ''Homo sapiens'' into the species that we have become. However, the association of Broca's area with language in modern man may guide further analysis of this evolution.
==See also==
* [[arcuate fasciculus]]
* [[Cerebral cortex|cortex]]
* [[expressive aphasia]]
* [[human brain]]
* [[language]]
* [[pars opercularis]]
* [[pars triangularis]]
* [[Wernicke's area]]
==References==
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{{Prosencephalon}}
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