Broca's area is a region of the brain The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as jellyfish and starfish have a decentralized nervous system without a brain, while sponges lack any nervous system at all. In vertebrates, the brain is located in the head, protected by the skull and close to the primary with functions linked to speech production Speech production is the process by which spoken words are selected to be produced, have their phonetics formulated and then finally are articulated by the motor system in the vocal apparatus. Speech production can be spontaneous such as when a person creates the words of a conversation, reaction such as when they name a picture or read aloud a.
The production of language Language is a term most commonly used to refer to so called "natural languages" — the forms of communication considered peculiar to humankind. By extension the term also refers to the type of human thought process which creates and uses language. Essential to both meanings is the systematic creation, maintenance and use of systems of has been linked to the Broca’s area since Paul Pierre Broca reported impairments in two patients. They had lost the ability to speak after injury to the posterior inferior frontal gyrus The inferior frontal gyrus is a gyrus of the frontal lobe of the human brain. Its superior border is the inferior frontal sulcus, its inferior border the lateral fissure, and its posterior border is the inferior precentral sulcus. Above it is the middle frontal gyrus, behind it the precentral gyrus of the brain.[1] Since then, the approximate region he identified has become known as Broca’s area, and the deficit in language production as Broca’s aphasia. Broca’s area is now typically defined in terms of the pars opercularis Superior frontal gyrus · Middle frontal gyrus (9l, 10l, 46) and pars triangularis of the inferior frontal gyrus A gyrus is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci, represented in Brodmann Korbinian Brodmann was a German neurologist who became famous for his definition of the cerebral cortex into 52 distinct regions from their cytoarchitectonic (histological) characteristics. These areas are now usually referred to as Brodmann areas. Some of these areas were later associated to nervous functions, such as areas 41 and 42 in the’s cytoarchitectonic Cytoarchitectonics is the study of the cellular composition of the body's tissues under the microscope. Applied particularly to the study of the central nervous system, cytoarchitectonics is one of the ways to parse the brain (along with gross anatomy, topography, receptor-binding autoradiography, immunohistochemistry, etc.), by obtaining sections map as areas 44 Brodmann area 44, or BA44, is part of the frontal cortex in the human brain. Situated just anterior to premotor cortex and on the lateral surface, inferior to BA9 and 45 Brodmann area 45 , is part of the frontal cortex in the human brain. Situated on the lateral surface, inferior to BA9 and adjacent to BA46.[1] Studies of chronic aphasia have implicated an essential role of Broca’s area in various speech and language functions. Further, functional MRI Magnetic resonance imaging , or nuclear magnetic resonance imaging (NMRI), is primarily a noninvasive medical imaging technique used in radiology to visualize detailed internal structure and limited function of the body. MRI provides much greater contrast between the different soft tissues of the body than computed tomography (CT) does, making it studies have also identified activation patterns in Broca’s area associated with various language tasks. However, slow destruction of the Broca's area by brain tumors A tumor or tumour is the name for a neoplasm or a solid lesion formed by an abnormal growth of cells which looks like a swelling. Tumor is not synonymous with cancer. A tumor can be benign, pre-malignant or malignant, whereas cancer is by definition malignant can leave speech relatively intact suggesting its functions can shift to nearby areas in the brain.[2]
Contents |
Anatomy and connectivity
Broca's area is often identified by visual inspection of the topography Topography is the study of Earth's surface shape and features or those of planets, moons, and asteroids. It is also the description of such surface shapes and features (especially their depiction in maps) of the brain either by macrostructural landmarks such as sulci In neuroanatomy, a sulcus is a depression or fissure in the surface of the brain. It surrounds the gyri, creating the characteristic appearance of the brain in humans and other large mammals or by the specification of coordinates in a particular reference space. The currently used Talairach and Tournoux atlas projects Brodmann Korbinian Brodmann was a German neurologist who became famous for his definition of the cerebral cortex into 52 distinct regions from their cytoarchitectonic (histological) characteristics. These areas are now usually referred to as Brodmann areas. Some of these areas were later associated to nervous functions, such as areas 41 and 42 in the's cytoarchitectonic map on to a template brain. Because Brodmann's parcelation was based on subjective visual inspection of cytoarchitectonic borders and also Brodmann analyzed only one hemisphere of one brain, the result is imprecise. Further, because of considerable variability across brains in terms of shape, size, and position relative to sulcal and gyral structure, a resulting localization precision is limited.[3]
Nevertheless, Broca’s area in the left hemisphere and its homologue in the right hemisphere A cerebral hemisphere is defined as one of the two regions of the brain that are delineated by the body's median plane, (medial 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 called the cerebral cortex that is supported by are designations usually used to refer to pars triangularis (PTr) and pars opercularis Superior frontal gyrus · Middle frontal gyrus (9l, 10l, 46) (POp) of the inferior frontal gyrus A gyrus is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci. The PTr and POp are defined by structural landmarks that only probabilistically divide the inferior frontal gyrus into anterior and posterior cytoarchitectonic areas of 45 and 44, respectively, by Brodmann’s classification scheme.[4]
Area 45 receives more afferent connections from prefrontal cortex, the superior temporal gyrus A gyrus is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci, and the superior temporal sulcus, compared to area 44, which tends to receive more afferent connections from motor, somatosensory The somatosensory system is a diverse sensory system comprising the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception (pain). The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal organs, and the cardiovascular system. While, and inferior parietal regions.[4]
The differences between area 45 and 44 in cytoarchitecture and in connectivity suggest that these areas might perform different functions. Indeed, recent neuroimaging Neuroimaging includes the use of various techniques to either directly or indirectly image the structure, function/pharmacology of the brain. It is a relatively new discipline within medicine and neuroscience/psychology studies have shown that the PTr and Pop, coressponding to areas 45 and 44, respectively, play different functional roles in the human with respect to language comprehension and action recognition/understanding.[4]
Broca's area revisited
In a recent study, the preserved brains of both Leborgne and Lelong (patients of Paul Pierre Broca) were reinspected using high-resolution volumetric MRI Magnetic resonance imaging , or nuclear magnetic resonance imaging (NMRI), is primarily a noninvasive medical imaging technique used in radiology to visualize detailed internal structure and limited function of the body. MRI provides much greater contrast between the different soft tissues of the body than computed tomography (CT) does, making it. The purpose of this study was to scan the brains in three dimensions and to identify the extent of both cortical and subcortical lesions in more detail. The study also sought to locate the exact site of the lesion in the frontal lobe in relation to what is now called Broca's area with the extent of subcortical involvement.[1]
Broca's patients
Leborgne
Leborgne was a patient of Paul Pierre Broca. He was unable to produce any words or phrases. The only word he could repetitively produce was 'tan'. After his death, a lesion was discovered on the surface of the left frontal lobe.
Lelong
Lelong was another patient of Paul Pierre Broca. He also exhibited reduced productive speech. He could only say five words, 'yes,' 'no,' 'three,' 'always,' and 'lelo' (a mispronunciation of his own name). At autopsy, a lesion was also found in the same region of lateral frontal lobe as in Leborgne. These two cases led Paul Pierre Broca to believe that speech was localized to this particular area.
MRI findings
Examination of the brains of Paul Pierre Broca's two historic patients with high resolution MRI Magnetic resonance imaging , or nuclear magnetic resonance imaging (NMRI), is primarily a noninvasive medical imaging technique used in radiology to visualize detailed internal structure and limited function of the body. MRI provides much greater contrast between the different soft tissues of the body than computed tomography (CT) does, making it has produced several interesting findings. First, the MRI findings suggest that other areas besides Broca's area may also have contributed to the patients' reduced productive speech. This finding is significant because it has been found that though lesions Because the definition of lesion is so broad, the varieties of lesions are virtually endless. They are subsequently classified by their features. If a lesion is caused by a tumor it will be classified as malignant versus benign. Lesions may be classified by the shape they form, as is the case with many ulcers, which can have a bullseye or 'target' to Broca's area alone can possibly cause temporary speech disruption, they do not result in severe speech arrest. Therefore, there is a possibility that the aphasia Aphasia is an acquired language disorder in which there is an impairment of any language modality. This may include difficulty in producing or comprehending spoken or written language denoted by Broca as an absence of productive speech also could have been influenced by the lesions in the other region. Another interesting finding is that the lesion, which was once considered to be critical for speech by Broca, is not precisely the same region as what is now known as Broca's area. This study provides further evidence that language and cognition are far more complicated than once thought and involve various networks of brain regions.
Speaking without Broca’s area
The essential role of the Broca's area in speech production has been questioned since it can be destroyed while leaving language nearly intact. In one case of a computer engineer a slow growing glioma A glioma is a type of tumor that starts in the brain or spine. It is called a glioma because it arises from glial cells. The most common site of gliomas is the brain was removed. The tumor and the surgery destroyed the left inferior The inferior frontal gyrus is a gyrus of the frontal lobe of the human brain. Its superior border is the inferior frontal sulcus, its inferior border the lateral fissure, and its posterior border is the inferior precentral sulcus. Above it is the middle frontal gyrus, behind it the precentral gyrus and middle frontal gyrus, the head of the caudate nucleus The caudate nucleus is a nucleus located within the basal ganglia of the brains of many animal species. The caudate nucleus is an important part of the brain's learning and memory system, the anterior limb of the internal capsule The internal capsule is an area of white matter in the brain that separates the caudate nucleus and the thalamus from the lenticular nucleus. The internal capsule contains both ascending and descending axons and the anterior insula. However there were minimal language problems three months after removal and the individual returned to his professional work. These minor problems include the inability to create syntactically complex sentences with including more than two subjects, multiple causal conjunctions or reported speech. These were explained by researchers as due to working memory Working memory is the executive and attentional aspect of short-term memory involved in the interim integration, processing, disposal, and retrieval of information. Working memory tasks include the active monitoring or manipulation of information or behaviors. It is a theoretical construct within cognitive psychology and neuroscience. Theories problems. They also attributed his lack of problems to extensive compensatory mechanisms enabled by neural plasticity in the nearby cerebral cortex and a shift of some functions to the homologous area in the right hemisphere.[2]
Functions
Language comprehension
For a long time, it was assumed that the role of Broca's area was more devoted to language production than language comprehension. However, recent evidence demonstrates that Broca's area also plays a significant role in language comprehension. Patients with lesions Because the definition of lesion is so broad, the varieties of lesions are virtually endless. They are subsequently classified by their features. If a lesion is caused by a tumor it will be classified as malignant versus benign. Lesions may be classified by the shape they form, as is the case with many ulcers, which can have a bullseye or 'target' in Broca's area who exhibit agrammatical speech production also show inability to use syntactic information to determine the meaning of sentences.[5] Also, a number of neuroimaging studies have implicated an involvement of Broca's area, particularly of the pars opercularis Superior frontal gyrus · Middle frontal gyrus (9l, 10l, 46) of the left inferior frontal gyrus A gyrus is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci, during the processing of complex sentences.[6] Further, it has recently been found in functional magnetic resonance imaging (fMRI Functional MRI or functional Magnetic Resonance Imaging is a type of specialized MRI scan. It measures the hemodynamic response (change in blood flow) related to neural activity in the brain or spinal cord of humans or other animals. It is one of the most recently developed forms of neuroimaging. Since the early 1990s, fMRI has come to dominate) experiments involving highly ambiguous sentences result in a more activated inferior frontal gyrus A gyrus is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci.[4] Therefore, the activity level in the inferior frontal gyrus and the level of lexical ambiguity are directly proportional to each other, because of the increased retrieval demands associated with highly ambiguous content.
Action recognition and production
Recent experiments have indicated that Broca's area is involved in various cognitive and perceptual tasks. One important contribution of Brodmann's area 44 is also found in the motor-related processes. Observation of meaningful hand shadows resembling moving animals activates frontal language area, demonstrating that Broca's area indeed plays a role in interpreting action of others.[7] An activation of BA 44 was also reported during execution of grasping and manipulation.[8]
Speech-associated gestures
It has been speculated that because speech-associated gestures could possibly reduce lexical or sentential ambiguity, comprehension should improve in the presence of speech-associated gestures. As a result of improved comprehension, the involvement of Broca's area should be reduced.[4]
Many neuroimaging studies have also shown activation of Broca's area when representing meaningful arm gestures. A recent study has shown evidence that word and gesture are related at the level of translation of particular gesture aspects such as goal and intention.[9] This finding that aspects of gestures are translated in words within Broca's area also explains language development in terms of evolution. Indeed, many authors have proposed that speech evolved from a primitive communication that arose from gestures.[7],[10] (see Evolution of Language below)
Aphasia
Aphasia Aphasia is an acquired language disorder in which there is an impairment of any language modality. This may include difficulty in producing or comprehending spoken or written language 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.[11]
Broca's aphasia vs. other aphasias
Patients with Broca's aphasia are individuals who know "what they want to say, they just cannot get it out." [11] They are typically able to understand what is being said to them, but unable to fluently speak. This is also known as non-fluent aphasia. Some of other symptoms may include problems with fluency, articulation, word-finding, word repetition, and producing and comprehending complex grammatical sentences, both orally and in writing.[1] These characteristics distinguish them from other individuals with other types of aphasia. Other aphasia types may have more difficulty understanding what is said to them. They may also struggle more with reading and writing than do individuals with Broca’s aphasia. While the individuals with Broca’s aphasia also have a good ability to self-monitor their language output, other types of aphasia may be more unaware of their language performance. Also, site of lesion Because the definition of lesion is so broad, the varieties of lesions are virtually endless. They are subsequently classified by their features. If a lesion is caused by a tumor it will be classified as malignant versus benign. Lesions may be classified by the shape they form, as is the case with many ulcers, which can have a bullseye or 'target' (brain damaged area) differs between the different aphasias.
Evolution of language
Several models have been proposed to explain the origin of human language. Human language is thought to have evolved Evolution is the change in the inherited traits of a population of organisms through successive generations. After a population splits into smaller groups, these groups evolve independently and may eventually diversify into new species. Ultimately, life is descended from a common ancestory through a long series of these speciation events, as the “evolutionary refinement of an implicit communication system already present in lower primates, based on a set of hand/mouth goal-directed action representations.”[7] The recent finding that Broca’s area is involved during meaningful action observation supports this idea. It was hypothesized that Broca’s area precursor was involved in generating action meanings by interpreting motor sequences in terms of goal. It was further argued that this ability might have been generalized during the evolution that gave this area the capability to deal with meanings. The activated frontal language areas when observing meaningful hand shadows resembling moving animals provides evidence that the human language may have evolved from neural substrates already involved in gestural recognition. Therefore, the study has demonstrated human Broca’s area as the motor center for speech, assembling and decoding communicative gestures. Consistent with this idea is that the neural substrate that regulated motor control in the common ancestor of apes and humans was most likely modified to enhance cognitive and linguistic ability.[10]
Another recent finding has showed significant areas of activation in subcortical and neocortical areas during the production of communicative manual gestures and vocal signals in chimpanzees.[12] Further, the data indicating that chimpanzees intentionally produce manual gestures as well as vocal signals to communicate with humans suggests that the precursors to human language are present at both the behavioral and neuronanatomical levels.
Additional images
See also
- Broca's aphasia
- Wernicke's area Wernicke's area is one of the two parts of the cerebral cortex linked since the late nineteenth century to speech (the other is the Broca's area). It is involved in the understanding of written and spoken language. It is traditionally considered to consist of the posterior section of the superior temporal gyrus in the dominant cerebral hemisphere (
- pars opercularis Superior frontal gyrus · Middle frontal gyrus (9l, 10l, 46)
- pars triangularis
References
- ^ a b c d N. F. Dronkers, O. Plaisant, M. T. Iba-Zizen, and E. A. Cabanis (2007). "Paul Broca's Historic Cases: High Resolution MR Imaging of the Brains of Leborgne and Lelong". Brain 130: 1432–1441. doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1093/brain/awm042. PMID A PMID is a unique number assigned to each PubMed citation of life sciences and biomedical scientific journal articles. The related Pubmed Central archive may additionally assign a separate number, a PMCID (PubMed Central Identifier), normally written with a PMC prefix 17405763.
- ^ a b Plaza M, Gatignol P, Leroy M, Duffau H. (2009). Speaking without Broca's area after tumor resection. Neurocase.9:1-17. PMID 19274574
- ^ Yosef Grodzinsky and Andrea Santi (2002). "The Battle for Broca's Region". Trends in Cognitive Sciences 12 (12): 474–480. doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1016/j.tics.2008.09.001. PMID A PMID is a unique number assigned to each PubMed citation of life sciences and biomedical scientific journal articles. The related Pubmed Central archive may additionally assign a separate number, a PMCID (PubMed Central Identifier), normally written with a PMC prefix 18930695.
- ^ a b c d e Jeremy I. Skipper, Susan Goldin-Meadow, Howard C. Nusbaum, and Steven L. Small (2007). "Speech-Associated Gestures, Broca's Area, and the Human Mirror System". Brain and Language 101: 260–277. doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1016/j.bandl.2007.02.008. PMID A PMID is a unique number assigned to each PubMed citation of life sciences and biomedical scientific journal articles. The related Pubmed Central archive may additionally assign a separate number, a PMCID (PubMed Central Identifier), normally written with a PMC prefix 17533001.
- ^ David Caplan (2006). "Why is Broca's Area Involved in Syntax?". Cortex 42: 469–471. PMID 16881251.
- ^ Tanja Crewe, Ina Bornkessel, Stefan Zysset, Richard Wiese, D. Yves von Cramon, and Matthias Schlesewksy (2005). "The Emergence of the Unmarked: A New Perspective on the Language-Specific Function of Broca's Area". Human Brain Mapping 26: 178–190. doi:10.1002/hbm.20154. PMID 15929098.
- ^ a b c Luciano Fadiga, Laila Craighero, Maddalena Fabbri Destro, Livio Finos, Nathalie Cotilon-Williams, Andrew T. Smith, and Umberto Castiello (2006). "Language in Shadow". Social Neuroscience 1 (2): 77–89. doi:10.1080/17470910600976430. PMID 18633777.
- ^ Luciano Fadiga and Laila Craighero (2006). "Hand Actions and Speech Representation In Broca's Area". Cortex 42: 486–490. PMID 16881255.
- ^ Maurizio Gentilucci, Paolo Bernardis, Girolamo Crisi, and Riccardo Dalla Volta (2006). "Repetitive Transcranial Magnetic Stimulation of Broca's Area Affects Verbal Responses to Gesture Observation". Journal of Cognitive Neuroscience 18 (7): 1059–1074. doi:10.1162/jocn.2006.18.7.1059. PMID 16839281.
- ^ a b Philip Lieberman (2002). "On the Nature and Evolution of the Neural Bases of Human Language". Yearbook of Physical Anthropology 45: 36–62. PMID 12653308.
- ^ a b c "What is Aphasia". Atlanta Aphasia Association. 2006. http://www.atlantaaphasia.org. Retrieved 2008-12-01.
- ^ Jared P. Taglialatela, Jamie L. Russell, Jennifer A. Schaeffer, and William D. Hopkins (2008). "Communicative Signaling Activates 'Broca's' Homolog in Chimpanzees". Current Biology 18: 343–348. doi:10.1016/j.cub.2008.01.049. PMID 18308569.
Categories: Brain
|
admin
Fri, 23 Apr 2010 18:00:10 GM
The battle for . Broca's Area. is expertly c; 2009-03-20 Spike activity. Quick links from the past week in mind and brain news:Wired reports that Japanese 'detergent suicide' technique creeps into U.S. To the bunkers! ...
