Editing Broca's area (section)

==Clinical significance==

===Stuttering===
A [[speech disorder]] known as [[stuttering]] is seen to be associated with underactivity in Broca's area.<ref>Maguire et al. 1994{{full citation needed|date=March 2018}}</ref><ref name=pmid9278544>{{cite journal | vauthors = Maguire EA, Frackowiak RS, Frith CD | title = Recalling routes around london: activation of the right hippocampus in taxi drivers | journal = The Journal of Neuroscience | volume = 17 | issue = 18 | pages = 7103–10 | date = September 1997 | pmid = 9278544 | pmc = 6573257 | doi = 10.1523/JNEUROSCI.17-18-07103.1997 }}</ref>

===Aphasia===
[[Aphasia]] is an acquired language disorder affecting all modalities such as writing, reading, speaking, and listening and results from brain damage. It is often a chronic condition that creates changes in all areas of one's life.<ref name="Ref4">{{Cite web|url=http://www.atlantaaphasia.org|title=What is Aphasia|access-date=2008-12-01|publisher=Atlanta Aphasia Association|year=2006|url-status=live|archive-url=https://web.archive.org/web/20081223230955/http://www.atlantaaphasia.org/|archive-date=2008-12-23}}</ref>

===Expressive aphasia vs. other aphasias===
Patients with [[expressive aphasia]], also known as '''Broca's aphasia''', are individuals who know "what they want to say, they just cannot get it out".<ref name="Ref4" /> They are typically able to comprehend words, and sentences with a simple syntactic structure (see above), but are more or less unable to generate fluent speech. Other symptoms that may be present include problems with fluency, articulation, word-finding, [[word repetition]], and producing and comprehending complex grammatical sentences, both orally and in writing.<ref name="pmid17405763"/>

This specific group of symptoms distinguishes those who have expressive aphasia from individuals with other types of aphasia. There are several distinct "types" of aphasia, and each type is characterized by a different set of language deficits. Although those who have expressive aphasia tend to retain good spoken language comprehension, other types of aphasia can render patients completely unable to understand any language at all, unable to understand any spoken language ([[auditory verbal agnosia]]),<ref name=pmid6478188>{{cite journal | vauthors = Metz-Lutz MN, Dahl E | title = Analysis of word comprehension in a case of pure word deafness | journal = Brain and Language | volume = 23 | issue = 1 | pages = 13–25 | date = September 1984 | pmid = 6478188 | doi = 10.1016/0093-934X(84)90002-6 | s2cid = 39218546 }}</ref><ref name=pmid21093464>{{cite journal | vauthors = Slevc LR, Martin RC, Hamilton AC, Joanisse MF | title = Speech perception, rapid temporal processing, and the left hemisphere: a case study of unilateral pure word deafness | journal = Neuropsychologia | volume = 49 | issue = 2 | pages = 216–30 | date = January 2011 | pmid = 21093464 | pmc = 3031136 | doi = 10.1016/j.neuropsychologia.2010.11.009 }}</ref><ref name=Poeppel_2001>{{cite journal |doi=10.1207/s15516709cog2505_3 |title=Pure word deafness and the bilateral processing of the speech code |journal=Cognitive Science |volume=25 |issue=5 |pages=679–93 |year=2001 |last1=Poeppel |first1=David |doi-access=free }}</ref> whereas still other types preserve language comprehension, but with deficits. People with expressive aphasia may struggle less with reading and writing (see [[alexia (condition)|alexia]]) than those with other types of aphasia.<ref name=Carlson/>{{rp|480–500}} Although individuals with expressive aphasia tend to have a good ability to self-monitor their language output (they "hear what they say" and make corrections), other types of aphasics can seem entirely unaware of their language deficits.

In the classical sense, expressive aphasia is the result of injury to Broca's area; it is often the case that lesions in specific brain areas cause specific, [[dissociation (neuropsychology)|dissociable]] symptoms,<ref name="aphasiafacts">{{cite web|url=http://www.aphasia.org/Aphasia%20Facts/aphasia_facts.html|title=The National Aphasia Foundation|access-date=January 15, 2011|url-status=dead|archive-url=https://web.archive.org/web/20110122211354/http://aphasia.org/Aphasia%20Facts/aphasia_facts.html|archive-date=January 22, 2011}}</ref> although case studies show there is not always a one-to-one mapping between lesion location and aphasic symptoms.<ref name=pmid21093464/> The correlation between damage to certain specific brain areas (usually in the left hemisphere) and the development of specific types of aphasia makes it possible to deduce (albeit very roughly) the location of a suspected brain lesion based only on the presence (and severity) of a certain type of aphasia, though this is complicated by the possibility that a patient may have damage to a number of brain areas and may exhibit symptoms of more than one type of aphasia. The examination of lesion data in order to deduce which brain areas are essential in the normal functioning of certain aspects of cognition is called the deficit-lesion method; this method is especially important in the branch of [[neuroscience]] known as [[aphasiology]]. [[Cognitive science]] – to be specific, [[cognitive neuropsychology]] – are branches of neuroscience that also make extensive use of the deficit-lesion method.<ref name="cogsci">{{cite book |chapter=Evaluating Techniques for the Study of Brain Damage |chapter-url={{Google books|wGti6_4Qn_QC|page=165|plainurl=yes}} |pages=[https://archive.org/details/cognitivescience0000frie/page/165 165–6] |title=Cognitive science: an introduction to the study of mind |isbn=978-1-4129-2568-6 |last1=Friedenberg |first1=Jay |last2=Silverman |first2=Gordon |name-list-style=vanc |year=2006 |url=https://archive.org/details/cognitivescience0000frie/page/165 }}</ref>
{| class="wikitable sortable" 
|+ Major characteristics of different types of acute aphasia<ref name="Ref4" />
! Type of aphasia
! [[Speech repetition]]
! Naming
! Auditory comprehension
! Fluency
|-
| [[Expressive aphasia]]
| Moderate–severe
| Moderate–severe
| Mild difficulty
| Non-fluent, effortful, slow
|-
| [[Receptive aphasia]]
| Mild–severe
| Mild–severe
| Defective
| Fluent paraphasic
|-
| [[Conduction aphasia]]
| Poor
| Poor
| Relatively good
| Fluent
|-
| [[Mixed transcortical aphasia]]
| Moderate
| Poor
| Poor
| Non-fluent
|-
| [[Transcortical motor aphasia]]
| Good
| Mild–severe
| Mild
| Non-fluent
|-
| [[Transcortical sensory aphasia]]
| Good
| Moderate–severe
| Poor
| Fluent
|-
| [[Global aphasia]]
| Poor
| Poor
| Poor
| Non-fluent
|-
| [[Anomic aphasia]]
| Mild
| Moderate–severe
| Mild
| Fluent
|}

===Newer implications related to lesions in Broca's area===
Since studies carried out in the late 1970s<ref name=pmid565019>{{cite journal | vauthors = Mohr JP, Pessin MS, Finkelstein S, Funkenstein HH, Duncan GW, Davis KR | title = Broca aphasia: pathologic and clinical | journal = Neurology | volume = 28 | issue = 4 | pages = 311–24 | date = April 1978 | pmid = 565019 | doi = 10.1212/WNL.28.4.311 | s2cid = 34920053 }}</ref> it has been understood that the relationship between Broca's area and Broca's aphasia is not as consistent as once thought.<ref name=pmid12140086>{{cite journal | vauthors = Kaan E, Swaab TY | title = The brain circuitry of syntactic comprehension | journal = Trends in Cognitive Sciences | volume = 6 | issue = 8 | pages = 350–356 | date = August 2002 | pmid = 12140086 | doi = 10.1016/S1364-6613(02)01947-2 | s2cid = 18668619 }}</ref> Lesions to Broca's area alone do not result in Broca's aphasia, nor do Broca's aphasic patients necessarily have lesions in Broca's area.<ref>{{cite journal | vauthors = Dronkers NF, Shapiro JK, Redfern B, Knight RT | year=1992 |title=The role of Broca's area in Broca's aphasia |journal=Journal of Clinical and Experimental Neuropsychology |volume=14 |pages=52–3 }}</ref> Lesions to Broca's area alone are known to produce a transient mutism that resolves within 3–6 weeks. This discovery suggests that Broca's area may be included in some aspect of verbalization or articulation; however, this does not address its part in sentence comprehension. Still, Broca's area frequently emerges in functional imaging studies of sentence processing.<ref name=pmid8810246>{{cite journal | vauthors = Just MA, Carpenter PA, Keller TA, Eddy WF, Thulborn KR | title = Brain activation modulated by sentence comprehension | journal = Science | volume = 274 | issue = 5284 | pages = 114–6 | date = October 1996 | pmid = 8810246 | doi = 10.1126/science.274.5284.114 | bibcode = 1996Sci...274..114J | s2cid = 30517695 }}</ref> However, it also becomes activated in word-level tasks.<ref name=pmid9710491>{{cite journal | vauthors = Friedman L, Kenny JT, Wise AL, Wu D, Stuve TA, Miller DA, Jesberger JA, Lewin JS | title = Brain activation during silent word generation evaluated with functional MRI | journal = Brain and Language | volume = 64 | issue = 2 | pages = 231–56 | date = September 1998 | pmid = 9710491 | doi = 10.1006/brln.1998.1953 | s2cid = 46640048 }}</ref> This suggests that Broca's area is not dedicated to [[sentence processing]] alone, but supports a function common to both. In fact, Broca's area can show activation in such non-linguistic tasks as imagery of motion.<ref name=pmid11144756>{{cite journal | vauthors = Binkofski F, Amunts K, Stephan KM, Posse S, Schormann T, Freund HJ, Zilles K, Seitz RJ | title = Broca's region subserves imagery of motion: a combined cytoarchitectonic and fMRI study | journal = Human Brain Mapping | volume = 11 | issue = 4 | pages = 273–85 | date = December 2000 | pmid = 11144756 | doi = 10.1002/1097-0193(200012)11:4<273::AID-HBM40>3.0.CO;2-0 | pmc = 6872088 | url = http://juser.fz-juelich.de/record/55170/files/2000_Binkofski_Posse_Broca%27s%20Region%20Subserves%20Imagery%20of%20Motion%20A%20Combined%20Cytoarchitectonic%20and%20.pdf }}</ref>

Considering the hypothesis that Broca's area may be most involved in articulation, its activation in all of these tasks may be due to subjects' covert articulation while formulating a response. Despite this caveat, a consensus seems to be forming that whatever role Broca's area may play, it may relate to known working memory functions of the frontal areas. (There is a wide distribution of [[Talairach coordinates]]<ref>{{cite book | vauthors = Talairach J, Tournoux P |year=1988 |title=Co-planar stereotaxic atlas of the human brain |location=New York |publisher=Thieme Medical |isbn=3137117011}}{{page needed|date=March 2018}}</ref> reported in the functional imaging literature that are referred to as part of Broca's area.) The processing of a passive voice sentence, for example, may require working memory to assist in the temporary retention of information while other relevant parts of the sentence are being manipulated (i.e. to resolve the assignment of thematic roles to arguments). Miyake, Carpenter, and Just have proposed that sentence processing relies on such general verbal working memory mechanisms, while Caplan and Waters consider Broca's area to be involved in working memory specifically for syntactic processing. Friederici (2002) breaks Broca's area into its component regions and suggests that Brodmann's area 44 is involved in working memory for both phonological<ref name=pmid15037129>{{cite journal | vauthors = Dronkers NF, Wilkins DP, Van Valin RD, Redfern BB, Jaeger JJ | title = Lesion analysis of the brain areas involved in language comprehension | journal = Cognition | volume = 92 | issue = 1–2 | pages = 145–77 | year = 2004 | pmid = 15037129 | doi = 10.1016/j.cognition.2003.11.002 | hdl = 11858/00-001M-0000-0012-6912-A | s2cid = 10919645 | hdl-access = free }}</ref> and syntactic structure. This area becomes active first for phonology and later for syntax as the time course for the comprehension process unfolds. Brodmann's area 45 and Brodmann's area 47 are viewed as being specifically involved in working memory for semantic features and thematic structure where processes of syntactic reanalysis and repair are required. These areas come online after Brodmann's area 44 has finished its processing role and are active when comprehension of complex sentences must rely on general memory resources. All of these theories indicate a move towards a view that syntactic comprehension problems arise from a computational rather than a conceptual deficit. Newer theories take a more dynamic view of how the brain integrates different linguistic and cognitive components and are examining the time course of these operations.

Neurocognitive studies have already implicated frontal areas adjacent to Broca's area as important for working memory in non-linguistic as well as linguistic tasks.<ref name=pmid10536086>{{cite journal | vauthors = D'Esposito M, Postle BR, Ballard D, Lease J | title = Maintenance versus manipulation of information held in working memory: an event-related fMRI study | journal = Brain and Cognition | volume = 41 | issue = 1 | pages = 66–86 | date = October 1999 | pmid = 10536086 | doi = 10.1006/brcg.1999.1096 | s2cid = 14336072 | doi-access = free }}</ref> Cabeza and Nyberg's analysis of imaging studies of working memory supports the view that BA45/47 is recruited for selecting or comparing information, while BA9/46 might be more involved in the manipulation of information in working memory. Since large lesions are typically required to produce a Broca's aphasia, it is likely that these regions may also become compromised in some patients and may contribute to their comprehension deficits for complex morphosyntactic structures.

====Broca's area as a key center in the linking of phonemic sequences====
Broca's area has been previously associated with a variety of processes, including phonological segmentation, syntactic processing, and unification, all of which involve segmenting and linking different types of linguistic information.<ref name=pmid15866191>{{cite journal | vauthors = Friederici AD | title = Towards a neural basis of auditory sentence processing | journal = Trends in Cognitive Sciences | volume = 6 | issue = 2 | pages = 78–84 | date = February 2002 | pmid = 15866191 | doi = 10.1016/S1364-6613(00)01839-8 | doi-access = free | hdl = 11858/00-001M-0000-0010-E573-8 | hdl-access = free }}</ref><ref name=pmid10936919>{{cite journal | vauthors = Burton MW, Small SL, Blumstein SE | title = The role of segmentation in phonological processing: an fMRI investigation | journal = Journal of Cognitive Neuroscience | volume = 12 | issue = 4 | pages = 679–90 | date = July 2000 | pmid = 10936919 | doi = 10.1162/089892900562309 | s2cid = 685383 }}</ref><ref name=pmid20961611>{{cite journal | vauthors = Flinker A, Chang EF, Barbaro NM, Berger MS, Knight RT | title = Sub-centimeter language organization in the human temporal lobe | journal = Brain and Language | volume = 117 | issue = 3 | pages = 103–9 | date = June 2011 | pmid = 20961611 | pmc = 3025271 | doi = 10.1016/j.bandl.2010.09.009 }}</ref> Although repeating and reading single words does not engage semantic and syntactic processing, it does require an operation linking phonemic sequences with motor gestures. Findings indicate that this linkage is coordinated by Broca's area through reciprocal interactions with temporal and frontal cortices responsible for phonemic and articulatory representations, respectively, including interactions with the motor cortex before the actual act of speech. Based on these unique findings, it has been proposed{{by whom|date=March 2018}} that Broca's area is not the seat of articulation, but rather is a key node in manipulating and forwarding neural information across large-scale cortical networks responsible for key components of speech production.{{citation needed|date=March 2018}}