The Broca's area it is a part of the brain that has traditionally been considered the "speech center." It is usually located in the left or dominant hemisphere, and is part of the frontal lobe.
Broca's area controls motor functions related to the production of speech. In people who have damage in this area, it is observed that they understand language, but cannot speak fluently or articulate words correctly.
There is another region in the brain called Wernicke's area that is responsible for language processing and understanding. It connects to Broca's area through a structure called the arcuate fasciculus..
Although Broca's area is currently known to play a critical role in the production of speech, scientists are still studying its exact function. For example, a study conducted at Johns Hopkins University has shown that Broca's area is activated before words are spoken and decreases in activity when the person begins to speak..
This seems to be the case because Broca's area is in charge of planning the chain of movements necessary to pronounce the words that we are going to say..
Traditionally, damage to and around Broca's area appears to produce Broca's aphasia. This is manifested by a little fluent speech, slow and with errors. The problem is in the pronunciation, preserving the meaning of the message.
This area was discovered in 1861 by the French neurosurgeon Paul Broca. This scientist examined the brains of patients with speech difficulties. Thus he verified that Broca's area is fundamental in the expression of language.
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Paul Broca published in 1861 a work on a patient named Leborgne who had begun to have speech problems in his 30s. Broca examined him when he was 51 years old and realized that the only expression he could articulate was "Tan.".
For this reason, this patient has been known as Monsieur Tan. He had a normal level of understanding, could express himself through gestures, and did not present any problems with the orcoarticulatory muscles.
After his death, it was found at his autopsy that he had extensive brain damage due to a rare condition called neurosyphilis, which is the result of untreated syphilis..
This infection affected the skull, meninges, and much of the left hemisphere. He also had a large abscess in the left third frontal gyrus.
Monsieur Tan's brain is preserved in the Dupuytren Museum in Paris.
In 1863 Broca published 25 cases of patients with speech disturbances and lesions in the left hemisphere. The third left frontal gyrus was also affected in almost all of them..
This led Broca to make his famous statement that "we speak with the left hemisphere." In addition to determining that there is a "language center" in the back of the frontal lobe of the brain.
From this study, Broca concluded that language articulation could be supported by the frontal gyrus; This is why this area has been called the Broca area. This was the first area of the brain to be associated with a function, in this case, with language..
Broca called the alteration related to damage in this area aphemia, although the term aphasia was later adopted..
Broca's area is in the left (or dominant) hemisphere of the brain. It is located above and behind the left eye, specifically, in the third frontal gyrus.
It is located just above Silvio's fissure and close to the anterior area of the motor cortex responsible for the movements of the face and mouth. According to Brodmann's map, this zone corresponds to areas 44 and 45.
This area is usually found in the left hemisphere, even in left-handed individuals. However, dominance of the right hemisphere can occur in approximately 4% of right-handed individuals. It can reach 27% in lefties. The following video shows where this brain area is:
Broca's area is divided into two: the pars opercularis (Brodmann's area 44) and the pars triangularis (Brodmann's area 45).
The pars opercularis works in conjunction with the pars triangularis to perform semantic tasks. Some studies seem to suggest that this area is more involved in phonological and syntactic processing. Other data indicate that pars opercularis participates in the perception of music.
This area tends to receive connections from lower parietal and somatosensory motor zones..
The pars triangularis occupies the triangular part of the inferior frontal gyrus. This region is activated in semantic tasks, for example, determining if a word belongs to a concrete or abstract entity.
It also seems to participate in generation tasks, that is, to evoke a verb related to a noun. For example, eat-apple. This area receives more connections from the prefrontal cortex, superior temporal gyrus, and superior temporal sulcus..
Some authors have pointed out that there is a “Broca complex”, which in addition to the previous ones, includes Brodmann's area 47.
Lately it has been proposed that it is part of Broca's area, in addition, area 46. Like area 6 (mainly, the supplementary motor area), which would extend towards the basal ganglia and the thalamus.
Research is ongoing to try to resolve the exact components of Broca's area..
The main function of Broca's area is the expression of language. Specifically, this area is linked to the production of speech, language processing and the control of movements of the face and mouth to be able to articulate words..
For a long time it has been thought that Broca's area was only dedicated to producing language. However, multiple studies show that Broca's area is also fundamental in understanding it..
This is seen in patients with lesions in this area that show ungrammatical speech production. That is, they are not able to order words to form meaningful sentences. For example, you can say “ball boy”, instead of “the boy is playing ball”.
Some neuroimaging studies have shown the activation of Broca's area pars opercularis during the processing of complex sentences..
In this way, Broca's area seems to react to the distinction of grammatically possible and impossible sentences, and is activated when faced with very ambiguous sentences..
In the latest research, using different techniques to precisely examine brain activity, it has been possible to determine that Broca's area is most active just before the words are spoken.
Some more specific functions of Broca's area are:
- Morphosyntax control. It is about the expression and understanding of syntactic structures, as well as the processing of verbs.
- It is responsible for planning and motor programming. That is, you develop a plan for the articulation, and then correct mistakes and make fluidity adjustments..
- Join the elements of the language so that the expression makes sense.
- Selecting the correct sounds, blocking or inhibiting "competing" sounds.
- Cognitive control to process the syntactic aspect of sentences.
- It also appears to participate in verbal working memory.
- Other authors have proposed that the most posterior parts of Broca's area, preferably, are in charge of performing language tasks based on phonological processing (organization of phonemes).
While the earlier regions would be involved in syntactic and semantic processing tasks.
- Broca's area also seems to influence the understanding of grammatical structures. For example, a patient with Broca's aphasia can understand simple sentences, but would have more problems if the grammatical structure increases their complexity..
- Recognize actions, for example, this area seems to be activated when shadows made with the hands that simulate animals are observed. This leads us to think that this area participates in the interpretation of the actions of others..
- Also, a part of Broca's area seems to influence the manipulation of objects..
- Gesticulation that accompanies speech. It seems that the gestures we make while we speak to reduce the ambiguity of the message, are translated into words in Broca's area.
Thus, this area interprets gestures by activating when they are represented. Therefore, when injuries occur in Broca's area in people who use sign language, they also have problems communicating with that language..
After Broca's studies, Carl Wernicke discovered another part of the brain that is involved in understanding language. This is located in the posterior part of the left temporal lobe. People who had an injury in that area could speak, but their speech was incoherent.
Wernicke's studies have been confirmed by subsequent studies. Neuroscientists agree that around the lateral sulcus (known as Silvio's fissure) of the left hemisphere of the brain, there is a kind of neural circuit involved in understanding and producing spoken language..
At the end of this circuit is Broca's area, which is associated with the production of language (language outputs). At the other extreme, in the posterior superior temporal lobe, is Wernicke's area, which is associated with the processing of the words we hear (language input).
Broca's area and Wernicke's area are connected by a large bundle of nerve fibers called the arcuate fasciculus..
Some studies have revealed that there is a third fundamental area in the language known as "Geschwind territory", which seems to be located in the lower parietal lobe. Neuroimaging studies have shown that this area is connected to Broca's and Wernicke's area through large bundles of nerve fibers..
Although the information can travel directly between Broca's and Wernicke's area through the arcuate fasciculus, the above indicates that there is a second parallel path that circulates through the inferior parietal lobe..
More recent studies have used direct recordings of the surface of the cerebral cortex in neurosurgical patients. They have found that when words are produced, Broca's area acts as an intermediary between the temporal cortex (which organizes incoming sensory information) and the motor cortex (which carries out mouth movements).
To make speech possible, it maintains connections with both structures. Broca's area coordinates the transformation of information through cortical networks involved in the production of spoken words. Thus, Broca's area formulates an “articulatory code” for the motor cortex to implement later..
Usually, an injury to the broca area leads to the famous Broca's aphasia. Patients with this condition have difficulty producing speech, maintaining understanding to a greater extent.
Speech is characterized by being slow, not very fluent, and grammatically incorrect. They also have trouble repeating sentences, as well as reading and writing. These patients often pronounce a few single words and short phrases with great effort.
Telegraphic language, consonant omissions and simplifications, and difficulties in forming compound verb tenses are common. They do not usually use functional terms such as "the", "in", "on", "with", etc..
They may have comprehension problems when the sentence is expressed in a more complex way. For example, this occurs with passive phrases such as "the cat was caressed by its owner".
However, these patients are aware of their limitations and may feel irritated and sad..
The most common cause of damage to Broca's area is strokes, especially those involving the left middle cerebral artery. This area is the one that supplies blood to the language areas.
However, Broca's area can also be affected by head injuries, tumors, infections, or brain surgery..
It is necessary to clarify that Broca's aphasia does not arise from only a localized lesion in Broca's area. It usually appears due to injuries both in this area and in adjacent areas (Brodmann areas 6, 8, 9, 10 and 26, and the insula).
It seems that if an injury were to occur that only covered Broca's area, an effect called "foreign accent" would be observed. These patients would have mild language fluency problems. In addition to difficulties in finding the necessary words.
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