Introduction
Broca’s area and its importance
While discussing how the language areas of the human brain are organized, it is necessary to consider some fundamentals concerning the interdependence between language and brain. First of all, there is a need to point out that the functions of language and their relation to the human brain were studied under abnormal circumstances, including brain damage, the effects of medicine on the brain, etc.
As far as scientists studied the relationship between language disorders and brain damage, one can conclude that scientists became familiar with each language area of the human brain. One of the most widespread speech disorders, which are caused by brain damage, is aphasia. The first man who started to study the interdependence between brain damage and language disorders was a Frenchman Paul Broca.
He identified “the third frontal gyrus of the cerebral cortex”, which is considered to be one of the language areas (Geschwind 2). This area controls not only the tongue, but the whole system of speech production, including the muscles of the face. The portion of the brain is known as the motor face area. However, one is to keep in mind that damage of Broca’s area does not lead to paralysis of face muscles and serious language disorders.
It can cause only mild weakness of the vocal cords. For this reason, one can conclude that the motor face area can be also controlled by the opposite side of the brain. At the end of the 19th century, Broca found that damage of the left half of the brain can cause certain disorders of spoken language; while damage of the right half of the brain does not impact on language abilities. This fact was confirmed by eight cases of the most common language disorder.
Wernicke’s aphasia
Another interesting issue, which should be noted, is that a person whose Broca’s area is damaged can sing songs. For this reason, it becomes evident that a mental condition, in which people are often unable to remember simple words or communicate, cannot be regarded as the result of the motor face area paralysis. In 1874, a new approach concerning a well-known language disorder appeared.
Thus, Carl Wernicke, who worked as a junior assistant in neurological centre, was well familiar with Broca’s conclusions on aphasia. However, he pointed out that damage of the left hemisphere of the human brain, which is placed outside the third frontal gyrus of the cerebral cortex can cause a language disorder differing from a disorder described by Broca.
For instance, one is to keep in mind that Broca’s aphasia is characterized by the so-called telegraphic speech (thereby, a person who suffers from aphasia cannot speak fast, the endings of verbs and nouns are usually omitted, it is extremely difficult to build long sentences and use sequence of tenses); while Wernicke’s aphasia seems to represent the opposite state, when a person’s speech is not low, grammar and articulation are not neglected, and the rhythm of the speech is also preserved.
However, a person who suffers with Wernicke’s aphasia relies on circumlocutory phrases, in order to build a sentence. For example, a patient can say: “Before I was in the one here, I was over in the other one. My sister had the department in the other one” (Geschwind 4). While speaking, a person who suffers from Wernicke’s aphasia uses descriptive ways to communicate. Thus, knife can be determined as “a thing, which is used to cut bread, meat, etc”.
Moreover, Wernicke’s language disorder is also characterized by verbal and literal paraphasia. Verbal paraphasia is considered to be a kind of a language disorder, when a person substitutes a word for another one, which has related or unrelated meaning.
For instance, the word fork can be replaced by the word spoon, or the word table can be replaced by the word chair. Literal paraphasia is a kind of a language disorder, when a person substitutes correct sounds for incorrect ones. For instance, the word wrench can be replaced by the word bench.
The key functions of Broca’s and Wernicke’s regions
One more difference between Broca’s aphasia and Wernicke’s language disorder is that damage of Broca’s area may cause no consequences in relation to speech comprehension; however, Wernicke is of completely different opinion, as he states that damage of the left hemisphere outside the third frontal gyrus of the cerebral cortex can lead to a severe loss of speech understanding.
Wernicke explains the phenomenon by the connections between the language areas. Thus, it is necessary to notice that both areas are connected by the articulate fasciculus. Taking into account the fact that Wernicke’s area receives auditory stimuli, it becomes obvious that the repetition of some words influences a bundle of nerve fibers and the auditory patterns are relayed to the third frontal gyrus.
On the other hand, written language comprehension depends upon the connections between the visual area of the human brain and its speech regions. The angular gyrus is the portion of the brain, which is responsible for the function.
So, when a person hears a word, one can make a conclusion that a word is accepted by Wernicke’s area. On the other hand, if a word is spoken, one can conclude that it is Broca’s area, which works. While speaking the muscles of the speech are controlled by the motor area. If one is to spell a word, the auditory patterns are relayed to the angular gyrus, which irritates Wernicke’s area.
In other words, it seems to be obvious that speech comprehension depends upon both Broca’s area and Wernicke’s region. If one of the portions of the brain is damaged, certain functions of language seem to be also broken. Taking into account the connections between both areas, one can suppose that the only way deaf people accept language is written; so, Wernicke’s area does not perform any functions.
Actually, there is a need to point out that “sign languages are highly structured linguistic systems with all the grammatical complexity of spoken languages” (Hickok et al., 48). The most interesting fact, however, is that deaf people can learn foreign sign languages and they can sign a second or a third foreign language with a foreign accent.
The principal difference between sign and spoken languages is that sign languages are based on visual-spatial changes; while spoken languages are based on acoustic-temporal ones. Generally, it is necessary to point out that certain damages of Wernicke’s area can cause serious problems with both written and spoken languages.
Thus, one can probably notice that some people cannot reproduce (speak or repeat) certain words, sentences, etc. Moreover, they cannot write correctly. If in such cases a person’s speech is still fluent, the third frontal gyrus seems to be intact. On the other hand, if Broca’s area is damaged, a person’s speech will be slow and labored. One is to take into account that if the damage were in Wernicke’s opposite area, the level of comprehension would remain the same.
The lesions in other portions of the brain can cause other types of aphasia. For instance, if Wernicke’s area is disconnected with Broca’s area, a person can speak fluently; however, his or her speech will be still abnormal. In other words, one can imagine that both areas are preserved, but they do not interact with each other. Thus, it is obvious that there are the channels between the areas, which are damaged.
Several arteries provide cerebral portions of the human brain with blood. The middle cerebral artery provides the speech centers of the brain with blood. The visual portions of the brain are nourished by the posterior cerebral artery.
Inadequate oxygen supply is usually observed in the so-called border zones. “Isolation of speech area by a large C-shaped lesion produced a remarkable syndrome in a woman who suffered from severe carbon monoxide poisoning” (Geschwind 5). The kind of damage led to inability to understand the semantic meaning of words; although new lexical unites could be easily remembered.
Conclusion
“In human beings, it is the left hemisphere that usually contains the specialized language areas” (Boeree par. 2). The inability to produce speech is usually caused by certain damages of the human brain. The most widespread language disorders include Wernicke’s aphasia, Broca’s aphasia, alexia, agraphia, dyslexia.
The last three disorders are caused by damages of the angular gyrus. Thus, if a person experiences some difficulties with reading, one can conclude that he or she suffers from dyslexia. Agraphia is a kind of a language disorder, when a person cannot write. A person’s inability to read is called alexia.
Works Cited
Boeree, George. Speech and the Brain, 2004. Web. <http://webspace.ship.edu/cgboer/speechbrain.html>.
Geschwind, Norman. Language and the Brain, 1972. Web.
Hickok, Gregory, Ursula Bellugi, and Edward Klima. Sign Language in the Brain, 2002. Web. <http://lcn.salk.edu/publications/2008/HIckok_Sci_Amer_SI_2002.pdf>.