One of the pioneers of this research was a French neurologist named Paul Broca. During the early s, Paul Broca discovered a region of the brain associated with the production of spoken language. He found that damage to this area resulted in problems producing language. Broca described how one patient known as Leborgne could understand language although he could not speak aside from isolated words and a few other utterances. When Leborgne died, Broca conducted a postmortem exam on the man's brain and found a lesion in an area of the frontal lobe.
This area of the brain is now referred to as Broca's area and is associated with the production of speech. About 10 years later, a neurologist named Carl Wernicke identified a similar type of problem in which patients were able to speak but were not able to actually comprehend language.
Examining the brains of patients suffering from this language problem revealed lesions at a junction of the parietal, temporal, and occipital lobes. This region of the brain is now known as Wernicke's area and is associated with the understanding of spoken and written language.
An aphasia is an impairment of language that affects an individual's ability to comprehend and produce both spoken and written communication. This type of aphasia is known as Wernicke's aphasia but is also sometimes referred to as fluent aphasia, sensory aphasia, or receptive aphasia. Wernicke's aphasia is a language disorder that impacts language comprehension and the production of meaningful language due to damage to the Wernicke's area of the brain.
According to the National Aphasia Association, people with Wernicke's aphasia can frequently produce speech that sounds normal and grammatically correct. The actual content of this speech makes little sense. Non-existent and irrelevant words are often included in the sentences that these individuals produce. Symptoms of Wernicke's aphasia include:. Individuals with Wernicke's aphasia have difficulty understanding spoken language but are able to produce sounds, phrases, and word sequences.
While these utterances have the same rhythm as normal speech, they are not a language because no information is conveyed. This type of aphasia affects both spoken and written language. Strokes are one of the most common causes, but Wernicke's aphasia can also be the result of traumatic brain injury, neurological disorders, brain tumors, and brain infections.
It was originally believed that Wernicke's area was responsible for making meaningful speech, while Broca's area was believed to be responsible for actually turning speech into comprehensible vocalizations. Today, researchers understand that language comprehension and production is a complex process that involves a network of different regions of the brain. For example, studies suggest that Wernicke's area plays a role in the comprehension of meaningful speech as well as a part in speech production itself.
Moreover, the entire group of areas decodes the structure of difficult sentences, the second one decodes the structure of easy, simple sentences, and the third group of areas is responsible for the meaning of the words.
These processes happen whether we talk or listen. These regions are positioned in the Brocas and the Wernickes areas , as well as the anterior portion of the temporal lobe. Furthermore, they are located in several parts of the anterior lobe, as well as the inferior parietal lobe. Remarkably, according to what we know today, the occipital lobe is not involved in speech processing at all. In the 19th century, neuroscientists were trying to discover and localize functions and abilities in our brain and relate them to their responsible centers.
One of the areas of their interest was language production, processing, and understanding. Paul Broca was one of the pioneers when it comes to language centers research. In the early s, he made a remarkable discovery. Namely, he identified the brain region responsible for language production.
Paul Broca also made research on patients with problems in producing language, especially in cases when they do understand the language but cannot speak. Broca found that lesions in a specific part of the frontal lobe lead to that very disorder.
The other key neuroscientist of the 19th century is German neurologist, Carl Wernicke, as mentioned in the introduction. This neurologist was interested in patients with a similar, yet so different problem. Wernickes patients were able to speak but their speech was meaningless.
In addition, they were not able to understand, i. Wernicke was devoted to examining the brains of these patients. He found lesions in an area located between the temporal, parietal, and occipital lobes, we today know as the Wernickes area. It was proven that this brain region is responsible for language comprehension and the production of meaningful speech. The arteries that make up the circle of Willis are divided into an anterior group and a posterior group.
The orientation of the circle is shown in the illustration below. In order to make the illustrations above and below easier to understand, the arteries are cut off at the ends where they disappear from view, change direction, or are no longer considered to be part of the circle of Willis. The blood vessels that make up the circulatory system are actually continuous.
They branch and merge and change in diameter and direction, but they never simply end. The anterior group of arteries in the circle of Willis consists of the following blood vessels. Blood is sent from the heart to the brain through the two internal carotid arteries and the two vertebral arteries. If you have a problem speaking or understanding speech, its a condition called aphasia. If you have trouble putting together the correct muscle movements necessary to produce speech, its a condition called.
Both aphasia and apraxia are most often caused by a stroke or trauma to the brain, usually when the left side of the brain is affected. Other less common causes are brain tumors and infections.
Broca's aphasia results from damage to a part of the brain called Broca's area, which is located in the frontal lobe, usually on the left side. Broca's area and Wernicke's area are connected by a bundle of nerve fibers called the arcuate fasciculus. Damage to the arcuate fasciculus causes a disorder called conduction aphasia. From the primary visual cortex, information is transmitted to the posterior speech area, including Wernicke's area.
Damage caused to Wernicke's area results in receptive, fluent aphasia. This means that the person with aphasia will be able to fluently connect words, but the phrases will lack meaning. This is unlike non-fluent aphasia, in which the person will use meaningful words, but in a non-fluent, telegraphic manner. Dysphasia is a speech disorder in which there is impairment of the power of expression by speech, writing, or signs, or impairment of the power of comprehension of spoken or written language.
More severe forms of dysphasia are called aphasia. Expressive aphasia, also known as Broca's aphasia, is a type of aphasia characterized by partial loss of the ability to produce language spoken, manual, or written , although comprehension generally remains intact.
A person with expressive aphasia will exhibit effortful speech. According to this model, written word information first arrives from the eyes to the occipital lobe within the primary visual cortex. This is a neuronal tract made up of white matter bundles , which is used to connect the frontal, parietal, and temporal lobes. The arcuate fasciculus therefore acts as a pathway between the two main language areas of the brain. The Wernicke-Geschwind model is now largely obsolete due to inconsistencies in neuroimaging studies.
However, this model has been useful in directing research and providing understanding that there are multiple brain regions involved in language, rather than one specific region completing all language functions. Wernicke, as well as Broca were one of the earlier advocators for the idea of lateralization of brain functions. This is the perspective that functions of the brain are performed by specific areas, rather than the holistic view that all brain functions are completed by the brain as a whole.
This holistic view was more widely accepted at the time, until researchers like Wernicke and Broca provided strong evidence against this. Specifically, these researchers offered insight into how the left and right cerebral hemispheres are not so similar to each other.
They provided support for the idea that language functions are typically more localised to the left cerebral hemisphere in the majority of individuals. Now, researchers understand that language comprehension and production are a more complicated process, involving a range of different brain networks. Before information about language is sent, the individual must activate prior knowledge regarding the sequences of speech sounds phonemes that form the words that need to be spoken.
This mental stage before articulation is known as phonological retrieval. Overall, language is a very complex behavior which is made possible by a range of functions such as comprehension, retrieval of phonemes, and articulation.
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