Broca's area
Encyclopedia
Broca's area is a region of the hominid brain
with functions linked to speech production
.
The production of language
has been linked to the Broca’s area since Pierre Paul Broca reported impairments in two patients. They had lost the ability to speak after injury to the posterior inferior frontal gyrus
of the brain. 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
and pars triangularis
of the inferior frontal gyrus
, represented in Brodmann’s
cytoarchitectonic map
as areas 44
and 45
of the dominant hemisphere. Studies of chronic aphasia have implicated an essential role of Broca’s area in various speech and language functions. Further, functional MRI 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 tumor
s can leave speech relatively intact suggesting its functions can shift to nearby areas in the brain.
of the brain either by macrostructural landmarks such as sulci
or by the specification of coordinates in a particular reference space. The currently used Talairach and Tournoux atlas projects Brodmann's
cytoarchitectonic map
onto 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.
Nevertheless, Broca’s area in the left hemisphere and its homologue in the right hemisphere
are designations usually used to refer to pars triangularis
(PTr) and pars opercularis
(POp) of the inferior frontal gyrus
. 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.
Area 45 receives more afferent connections from prefrontal cortex, the superior temporal gyrus
, and the superior temporal sulcus, compared to area 44, which tends to receive more afferent connections from motor, somatosensory, and inferior parietal regions.
The differences between area 45 and 44 in cytoarchitecture and in connectivity suggest that these areas might perform different functions. Indeed, recent neuroimaging
studies have shown that the PTr and Pop, corresponding to areas 45 and 44, respectively, play different functional roles in the human with respect to language comprehension and action recognition/understanding.
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 region, 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.
was removed. The tumor and the surgery destroyed the left inferior
and middle frontal gyrus
, the head of the caudate nucleus
, the anterior limb of the internal capsule
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 including more than two subjects, multiple causal conjunction
s or reported speech. These were explained by researchers as due to working memory
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.
of the left inferior frontal gyrus
, during the processing of complex sentences. Further, it has recently been found in functional magnetic resonance imaging (fMRI) experiments involving highly ambiguous sentences result in a more activated inferior frontal gyrus
. 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.
'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. An activation of BA 44 was also reported during execution of grasping and manipulation.
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 its motor goal
and intention. 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. (See below.)
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.
This specific group of symptoms distinguishes Broca's aphasics 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. While Broca's aphasics 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 (pure word deafness
), while still other types preserve language comprehension, but with deficits. People with Broca's aphasia may struggle less with reading and writing (see alexia
) than those with other types of aphasia. While individuals with Broca’s 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 oblivious to their language deficits.
Broca's aphasia classically is the result of injury to Broca's area; it is often the case that lesions in specific brain areas cause specific, dissociable
symptoms, although case studies show there is not always a one-to-one mapping between lesion location and aphasic symptoms. 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
- specifically cognitive neuropsychology
- are branches of neuroscience that also make extensive use of the deficit-lesion method.
in humans has led to the consideration of a number of evolutionary "models". These models attempt to show how modern language might have evolved, and a common feature of many of these theories is the idea that vocal communication
was initially used to complement a far more dominant mode of communication through gesture. Human language might have evolved
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."
"Hand/mouth goal-directed action representations" is another way of saying "gestural communication", "gestural language", or "communication through body language." The recent finding that Broca’s area is active when people are observing others engaged in meaningful action is evidence in support of this idea. It was hypothesized that a precursor to the modern Broca’s area was involved in translating gestures into abstract ideas by interpreting the movements of others as meaningful action with an intelligent purpose. It is argued that over time the ability to predict the intended outcome and purpose of a set of movements eventually gave this area the capability to deal with truly abstract ideas, and therefore (eventually) became capable of associating sounds (words) with abstract meanings. The observation that frontal language areas are activated when people observe Hand Shadows is further evidence that human language may have evolved from existing neural substrates that evolved for the purpose of gesture recognition. The study therefore claims that Broca’s area is the "motor center for speech", which assembles and decodes speech sounds in the same way it interprets body language and 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. Studies of deaf "speakers" of American Sign Language
and English speakers suggest that the human brain recruited systems that had evolved to perform more basic functions much earlier; these various brain circuits, according to the authors, were tapped to work together in creating language.
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. Further, the data indicating that chimpanzee
s 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.
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
with functions linked to speech production
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...
.
The production of language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...
has been linked to the Broca’s area since Pierre Paul Broca reported impairments in two patients. They had lost the ability to speak after injury to the posterior inferior frontal gyrus
Inferior frontal gyrus
The inferior frontal gyrus is a gyrus of the frontal lobe . It is labelled gyrus frontalis inferior, its Latin name...
of the brain. 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
Pars opercularis
In the human brain the Pars opercularis is the part of the inferior frontal gyrus that lies between the inferior precentral sulcus and the ascending ramus of the lateral sulcus. It is called opercularis because it covers part of the insula. The pars opercularis together with the pars triangularis...
and pars triangularis
Pars triangularis
Pars triangularis is a region of the human cortex, located in the inferior frontal gyrus of the frontal lobe in the corresponding Brodmann area 45...
of the inferior frontal gyrus
Gyrus
A gyrus is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci .-Notable gyri:* Superior frontal gyrus, lat. gyrus frontalis superior* Middle frontal gyrus, lat. gyrus frontalis medius...
, represented in Brodmann’s
Korbinian Brodmann
Korbinian Brodmann was a German neurologist who became famous for his definition of the cerebral cortex into 52 distinct regions from their cytoarchitectonic characteristics.-Life:...
cytoarchitectonic map
Brodmann area
A Brodmann area is a region of the cerebral cortex defined based on its cytoarchitectonics, or structure and organization of cells.-History:...
as areas 44
Brodmann area 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
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.This area is also known as pars triangular ...
of the dominant hemisphere. Studies of chronic aphasia have implicated an essential role of Broca’s area in various speech and language functions. Further, functional MRI 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 tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
s can leave speech relatively intact suggesting its functions can shift to nearby areas in the brain.
Anatomy and connectivity
Broca's area is often identified by visual inspection of the topographyTopography
Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
of the brain either by macrostructural landmarks such as sulci
Sulcus (neuroanatomy)
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's
Korbinian Brodmann
Korbinian Brodmann was a German neurologist who became famous for his definition of the cerebral cortex into 52 distinct regions from their cytoarchitectonic characteristics.-Life:...
cytoarchitectonic map
Brodmann area
A Brodmann area is a region of the cerebral cortex defined based on its cytoarchitectonics, or structure and organization of cells.-History:...
onto 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.
Nevertheless, Broca’s area in the left hemisphere and its homologue in the right hemisphere
Cerebral hemisphere
A cerebral hemisphere is one of the two regions of the eutherian brain that are delineated by the median plane, . 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...
are designations usually used to refer to pars triangularis
Pars triangularis
Pars triangularis is a region of the human cortex, located in the inferior frontal gyrus of the frontal lobe in the corresponding Brodmann area 45...
(PTr) and pars opercularis
Pars opercularis
In the human brain the Pars opercularis is the part of the inferior frontal gyrus that lies between the inferior precentral sulcus and the ascending ramus of the lateral sulcus. It is called opercularis because it covers part of the insula. The pars opercularis together with the pars triangularis...
(POp) of the inferior frontal gyrus
Gyrus
A gyrus is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci .-Notable gyri:* Superior frontal gyrus, lat. gyrus frontalis superior* Middle frontal gyrus, lat. gyrus frontalis medius...
. 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
Brodmann
Brodmann may refer to:* Korbinian Brodmann, German neurologist* Brodmann area, a region in the brain cortex...
’s classification scheme.
Area 45 receives more afferent connections from prefrontal cortex, the superior temporal gyrus
Sulcus (neuroanatomy)
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....
, and the superior temporal sulcus, compared to area 44, which tends to receive more afferent connections from motor, somatosensory, and inferior parietal regions.
The differences between area 45 and 44 in cytoarchitecture and in connectivity suggest that these areas might perform different functions. Indeed, recent neuroimaging
Neuroimaging
Neuroimaging includes the use of various techniques to either directly or indirectly image the structure, function/pharmacology of the brain...
studies have shown that the PTr and Pop, corresponding to areas 45 and 44, respectively, play different functional roles in the human with respect to language comprehension and action recognition/understanding.
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. 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.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 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 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 aphasiaAphasia
Aphasia is an impairment of language ability. This class of language disorder ranges from having difficulty remembering words to being completely unable to speak, read, or write....
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 region, 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 gliomaGlioma
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.-By type of cell:...
was removed. The tumor and the surgery destroyed the left inferior
Inferior frontal gyrus
The inferior frontal gyrus is a gyrus of the frontal lobe . It is labelled gyrus frontalis inferior, its Latin name...
and middle frontal gyrus
Middle frontal gyrus
The middle frontal gyrus makes up about one-third of the frontal lobe of the human brain....
, the head of the caudate nucleus
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.-Anatomy:...
, the anterior limb of the internal capsule
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
Insular cortex
In each hemisphere of the mammalian brain the insular cortex is a portion of the cerebral cortex folded deep within the lateral sulcus between the temporal lobe and the frontal lobe. The cortical area overlying it towards the lateral surface of the brain is the operculum...
. 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 including more than two subjects, multiple causal conjunction
Conjunction
Conjunction can refer to:* Conjunction , an astronomical phenomenon* Astrological aspect, an aspect in horoscopic astrology* Conjunction , a part of speech** Conjunctive mood , same as subjunctive mood...
s or reported speech. These were explained by researchers as due to working memory
Working memory
Working memory has been defined as the system which actively holds information in the mind to do verbal and nonverbal tasks such as reasoning and comprehension, and to make it available for further information processing...
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.
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 in Broca's area who exhibit agrammatical speech production also show inability to use syntactic information to determine the meaning of sentences. Also, a number of neuroimaging studies have implicated an involvement of Broca's area, particularly of the pars opercularisPars opercularis
In the human brain the Pars opercularis is the part of the inferior frontal gyrus that lies between the inferior precentral sulcus and the ascending ramus of the lateral sulcus. It is called opercularis because it covers part of the insula. The pars opercularis together with the pars triangularis...
of the left inferior frontal gyrus
Gyrus
A gyrus is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci .-Notable gyri:* Superior frontal gyrus, lat. gyrus frontalis superior* Middle frontal gyrus, lat. gyrus frontalis medius...
, during the processing of complex sentences. Further, it has recently been found in functional magnetic resonance imaging (fMRI) experiments involving highly ambiguous sentences result in a more activated inferior frontal gyrus
Gyrus
A gyrus is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci .-Notable gyri:* Superior frontal gyrus, lat. gyrus frontalis superior* Middle frontal gyrus, lat. gyrus frontalis medius...
. 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 BrodmannBrodmann
Brodmann may refer to:* Korbinian Brodmann, German neurologist* Brodmann area, a region in the brain cortex...
'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. An activation of BA 44 was also reported during execution of grasping and manipulation.
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.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 its motor goal
Motor goal
A motor goal is a neurally planned motor outcome that is used to organize motor control.Motor goals are experimentally shown to exist since planned movements can when disrupted adjust to achieve their planned outcome...
and intention. 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. (See below.)
Aphasia
AphasiaAphasia
Aphasia is an impairment of language ability. This class of language disorder ranges from having difficulty remembering words to being completely unable to speak, read, or write....
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.
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." 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. 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.This specific group of symptoms distinguishes Broca's aphasics 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. While Broca's aphasics 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 (pure word deafness
Pure word deafness
Pure Word Deafness is caused by bilateral damage to the posterior superior temporal lobes or disruption of connections between these areas. It exhibits itself as inability to comprehend the meaning of speech, but still being able to hear, speak, read, and write.-Presentation:The underlying...
), while still other types preserve language comprehension, but with deficits. People with Broca's aphasia may struggle less with reading and writing (see alexia
Alexia
Alexia may refer to:People*Alexia *Alexia *Alexia Bryn, a Norwegian pair skater*Alexia Dechaume-Balleret, a French professional tennis player...
) than those with other types of aphasia. While individuals with Broca’s 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 oblivious to their language deficits.
Broca's aphasia classically is the result of injury to Broca's area; it is often the case that lesions in specific brain areas cause specific, dissociable
Dissociation (neuropsychology)
In neuropsychology, dissociation involves identifying the neural substrate of a particular brain function through identification of case studies, neuroimaging, or neuropsychological testing.-Single dissociation:...
symptoms, although case studies show there is not always a one-to-one mapping between lesion location and aphasic symptoms. 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
Neuroscience
Neuroscience is the scientific study of the nervous system. Traditionally, neuroscience has been seen as a branch of biology. However, it is currently an interdisciplinary science that collaborates with other fields such as chemistry, computer science, engineering, linguistics, mathematics,...
known as aphasiology
Aphasiology
Aphasiology is the study of linguistic problems resulting from brain damage. It is also the name of a scientific journal covering the area.These specific deficits, termed aphasias, may be defined as impairments of language production or comprehension that cannot be attributed to trivial causes...
. Cognitive science
Cognitive science
Cognitive science is the interdisciplinary scientific study of mind and its processes. It examines what cognition is, what it does and how it works. It includes research on how information is processed , represented, and transformed in behaviour, nervous system or machine...
- specifically cognitive neuropsychology
Cognitive neuropsychology
Cognitive neuropsychology is a branch of cognitive psychology that aims to understand how the structure and function of the brain relates to specific psychological processes. It places a particular emphasis on studying the cognitive effects of brain injury or neurological illness with a view to...
- are branches of neuroscience that also make extensive use of the deficit-lesion method.
| Type of Aphasia | Repetition | Naming | Auditory Comprehension | Fluency |
|---|---|---|---|---|
| Broca's | Mod-severe | Mod-severe | Mild difficulty | Non-fluent, effortful, slow |
| Wernicke's Receptive aphasia Receptive aphasia, also known as Wernicke’s aphasia, fluent aphasia, or sensory aphasia, is a type of aphasia traditionally associated with neurological damage to Wernicke’s area in the brain,... |
Mild-severe | Mild-severe | Defective | Fluent paraphasic |
| Conduction Conduction aphasia Conduction aphasia, also called associative aphasia, is a relatively rare form of aphasia. An acquired language disorder, it is characterized by intact auditory comprehension, fluent speech production, but poor speech repetition. Patients will display frequent errors during spontaneous speech,... |
Poor | Poor | Relatively good | Fluent |
| Mixed Transcortical | Moderate | Poor | Poor | Non-fluent |
| Transcortical Motor | Good | Mild-severe | Mild | Non-fluent |
| Transcortical Sensory | Good | Mod-severe | Poor | Fluent |
| Global | Poor | Poor | Poor | Non-fluent |
| Anomic Nominal aphasia Nominal aphasia is a severe problem with recalling words or names.Dysnomia refers to a less severe form of this word-recall dysfunction. Learning disabilities caused by name-recall problems are usually diagnosed as dysnomia rather than anomia.- Overview :Anomic aphasia is a type of aphasia... |
Mild | Mod-severe | Mild | Fluent |
Evolution of language
The pursuit of a satisfying theory that addresses the origin of languageOrigin of language
The origin of language is the emergence of language in the human species. This is a highly controversial topic. Empirical evidence is so limited that many regard it as unsuitable for serious scholars. In 1866, the Linguistic Society of Paris went so far as to ban debates on the subject...
in humans has led to the consideration of a number of evolutionary "models". These models attempt to show how modern language might have evolved, and a common feature of many of these theories is the idea that vocal communication
Communication
Communication is the activity of conveying meaningful information. Communication requires a sender, a message, and an intended recipient, although the receiver need not be present or aware of the sender's intent to communicate at the time of communication; thus communication can occur across vast...
was initially used to complement a far more dominant mode of communication through gesture. Human language might have evolved
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
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."
"Hand/mouth goal-directed action representations" is another way of saying "gestural communication", "gestural language", or "communication through body language." The recent finding that Broca’s area is active when people are observing others engaged in meaningful action is evidence in support of this idea. It was hypothesized that a precursor to the modern Broca’s area was involved in translating gestures into abstract ideas by interpreting the movements of others as meaningful action with an intelligent purpose. It is argued that over time the ability to predict the intended outcome and purpose of a set of movements eventually gave this area the capability to deal with truly abstract ideas, and therefore (eventually) became capable of associating sounds (words) with abstract meanings. The observation that frontal language areas are activated when people observe Hand Shadows is further evidence that human language may have evolved from existing neural substrates that evolved for the purpose of gesture recognition. The study therefore claims that Broca’s area is the "motor center for speech", which assembles and decodes speech sounds in the same way it interprets body language and 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. Studies of deaf "speakers" of American Sign Language
American Sign Language
American Sign Language, or ASL, for a time also called Ameslan, is the dominant sign language of Deaf Americans, including deaf communities in the United States, in the English-speaking parts of Canada, and in some regions of Mexico...
and English speakers suggest that the human brain recruited systems that had evolved to perform more basic functions much earlier; these various brain circuits, according to the authors, were tapped to work together in creating language.
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. Further, the data indicating that chimpanzee
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...
s 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.