Research Paper about Broca's Aphasia

📌Category: Health
📌Words: 1085
📌Pages: 4
📌Published: 13 April 2022

In 1861, Paul Broca helped establish cognitive neuropsychology by discovering the posterior part of the left inferior frontal cortex was involved in the production of speech. Finding that those who suffered damages in this area often experienced Broca's aphasia. Since then, however, technological advancements have provided new insight into the extent of the damage in the brains of those with Broca's aphasia, which is much larger than Broca had originally claimed.

In 1860, Paul Broca and his colleagues considered that language originated in the frontal lobes of the brain. Louis Leborgne was brought under the care of Broca shortly after this proposal and helped detect the location of speech in the brain. For twenty years, Leborgne was unable to pronounce any more than the word 'tan', which could change in tonality depending on how he felt at the time. Several days after Broca had him under his care, he passed away. A brain autopsy of Leborgne revealed damage to the inferior part of the left frontal lobe, which strengthened Broca's hypothesis that this area was involved in spoken language. Broca later encountered Lazare Lelong, a patient with a case like that of Leborgne. He had suffered a stroke one year earlier and only spoke five words: "oui", "non", "tois", 'toujours' and "lelo" (a mispronunciation of his name). Broca found that there had been damage done to the same region as Leborgne, so the area where these damages were found became known as Broca's area.

Broca's research helped establish cognitive neuropsychology. Cognitive neuropsychologists develop hypotheses and theories that explain psychological disorders and try to identify specific brain regions that process information. Broca and his colleagues examined claims made by phrenologists that certain brain areas had specific functions, and this led to the discussion Broca and his colleagues had regarding the area of language. We know from Broca's research that his area plays a crucial role in producing speech. His research furthered our understanding of brain structure and language by establishing the first link between a specific brain region and a specific function. The speech impairment is referred to as Broca's aphasia.

Broca's aphasia is a speech impairment caused by damage to Broca's area (left frontal lobe). Broca's aphasia is commonly associated with difficulties producing speech and speaking correctly in grammatical structures, which indicates severe brain damage. However, comprehension remains relatively intact. Broca's aphasia often co-occurs with motor disorders, such as apraxia or dysarthria, which can result in tongue and mouth coordination issues and muscle weakness, resulting in slurred and distorted speech. Goodglass published an example of how someone with Broca's aphasia would typically speak, "Monday ... dad and Paul... and dad ... hospital ... thirty minutes ... and yes ... ah ... hospital". And er… Wednesday…nine o’clock. And er Thursday ten o’clock doctors.’.

In 1874 neurologist Karl Wernicke released his findings on aphasia. He discovered his patients had a speech deficit opposite to what was described by Broca, he named this type of aphasia Wernicke’s aphasia, which is located in the left posterior, superior temporal gyrus. Wernicke’s aphasia was categorized by a deficit in comprehension of speech, semantics and often suggests moderate damage has been done to the brain. Carroll, 1999 stated that Wernicke’s aphasia would sound like ‘well, this is… mother is away here working out here to get her better, but when she’s looking, the two books looking in other part. One their small tile into her time here. She’ working another time’. Wernicke's explanation could explain the poor comprehension, but not why patients had difficulty speaking.

Our ability to study Broca's area has been aided by modern technology. Broca's area has been studied through brain imaging studies for about thirty years. We have been able to measure and record brain activity using functional magnetic resonance imaging (fMRI) and electroencephalograms (EEG). The results provide us with a more comprehensive picture of Broca's area. As a clarification, Broca never cut open the brains to examine the extent of the damage; instead, he preserved them in alcohol and sent them to Dupuytren's Museum. Broca stated during his examination that the damage extended into 'the small convolutions of the insula and the corpus striatum' and he was able to inspect 'half way into the anterior horn of Leborgne's left lateral ventricle', which implies Broca knew that the damage to Leborgne's brain did not end with the observable region. It wasn't until much later, when brain imaging studies became more common, that the depth of the damage was examined.                                                           

Many brain imaging studies are insufficiently spatially and temporally resolving to capture the brain activity in Broca's area. Speaking takes a few hundred milliseconds, but an FMRI takes one brain map per second, which means that it is too slow to capture brain activity. The problem with EEG is that the areas of the brain that are responsible for speech production are next to each other, so the image is too blurry to be useful. Fortunately, patients with brain tumors and epilepsy have often allowed researchers to get a good image of the brain activity by having electrodes placed directly in contact with their brains. This is because these medical conditions sometimes dictate the placement of electrodes directly on the brain. These electrodes have the same millisecond temporal resolution as EEG but with a special resolution and specificity that rivals that of FMRI.    

Seven epileptic patients were studied by Flinker and colleagues. Each needed surgery to remove the epileptic focus in their brain. Intracranial electrodes were used by Flinker to determine the size and origin of seizures; intracal electrodes were used to determine Broca's area's function. Flinker studied the auditory cortex, the motor cortex, and Broca's area while asking patients to repeat words, including pseudowords, to examine these regions. Once speaking had begun, the auditory cortex was most active, closely followed by activity in Broca's area. However, once speaking started the activity had stopped, so the motor cortex became most active. Flinker demonstrated that the tongue and lips are controlled by the motor cortex. Dr Mathew Tate studied patients undergoing neurosurgery and asked them to repeat words with bursts of electrical simulation in the cerebral cortex. They found that tampering with Broca's area had little effect on the ability to speak.

 Researchers Dronkers et al and colleagues decided to scan Leborgne’s brain with a modern MRI machine to assess further damage that may have been done that was not observable to Broca, as I mentioned previously Broca inclined that the damage of his patients extended beyond what he could see, Dronkers found that the damage extended to the neighboring parietal and temporal lobes, reaching into the depth of the cerebral hemisphere and destroying most of the insula and part of the basal ganglia. Researchers showed that functions such as speech are not centralized in one area but are the result of interactions between brain regions which create a network, .

Broca's discoveries claimed a localizationist view of speech deficiencies. However, modern neuropsychology has shown that this is not the case and speech deficiencies are caused by much greater damage than originally thought. Broca’s discoveries are still important.

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