Broca’s area is recognized as one of the main language centers of the brain. This region is associated with the production of speech and written language, as well as being linked with the processing and comprehension of language.
The name of Broca’s area comes from French physician Paul Broca, whose work on language-impaired patients resulted in him discovering this language area. Anatomically, Broca’s area is located within the frontal lobes of the cerebral cortex.
Specifically, this area is considered part of a region called the inferior frontal gyrus, a gyrus is a ridge on the surface of the brain’s cortex. Some researchers believe that Broca’s makes up the entire inferior frontal gyrus, while others consider it to make up a portion of this region or expand slightly outside the inferior frontal gyrus.
Typically, Broca’s area is located within the dominant hemisphere of the frontal lobes, which is the left hemisphere in around 97% of people. In general, the brain’s left hemisphere is responsible for language and speech.
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Because of the discovery of Broca’s area, we also now have a better understanding of conditions that can affect language production.
If an individual is presenting difficulties with formulating speech and written word, has repetitive speech, or speaks in non-coherent sentences, we now can attribute damage to Broca’s area as a possible reason why these symptoms are being experienced.
What is Brain Lateralization
- Paul Broca was one of the earlier advocators for the idea of lateralization of brain function. Lateralization of brain function is the view that functions of the brain are performed by specific regions of the brain.
- Before this idea, it was generally accepted that the whole of the brain was used for every function, therefore people would have held the belief that language was produced in every region of the brain.
- Broca’s area is strong evidence that language functions of the brain are lateralized to specific brain regions. Specifically, it provided support for the idea that language functions are located in the dominant hemisphere of the brain, that being the left hemisphere in the majority of individuals.
Through modern neuroimaging techniques, researchers can now draw focus on the activity and structure of Broca’s area to better understand this area in more depth. The difference in the structure and function of Broca’s area can also be found in conditions that can affect language.
For instance, it has been suggested that language differences in those with Autism may correlate to differences in Broca’s area (Bauman & Kemper, 2005).
The precise importance of Broca’s area in the production of language is still up for debate. Evidence usually implies that damage to this area can impair language production, but there is still some uncertainty over what specific language function is lost as a result of damage.
It has been suggested that Broca’s area may play a role in the motor movements necessary for speech production, whilst others have suggested that Broca’s area may be involved with verbal working memory and grammar.
Connections to other brain areas
Another noteworthy language area located in the left hemisphere is Wernicke’s area. Wernicke’s area is located proximate to Broca’s area, within the upper temporal lobe.
Whilst Broca’s area has an important role in the production of speech, Wernicke’s area is important for the comprehension of language.
People with damage to Broca’s area may have difficulty formulating words and written language, whilst individuals who have damage to Wernicke’s area may not have difficulty producing language but may have difficulty understanding language.
The majority of the time, people with damaged Wernicke’s area will often speak fluently, in comparison to damage to Broca’s area, where language is non-fluent or broken up.
These two areas are close in proximity, typically in the left hemisphere of the brain, and are connected to each other via a neuronal tract called the arcuate fasciculus.
The arcuate fasciculus is a white matter bundle that contains both long and short fibers, which are used to connect the frontal, parietal, and temporal lobes.
This tract, therefore, acts as a pathway from Broca’s area in the frontal lobes and Wernicke’s area in the temporal lobes. The arcuate fasciculus has a role in syntax, which is a set of rules by which we order words within language.
It is believed that Wernicke’s area comprehends language and chooses the correct words to use. This is sent through the arcuate fasciculus to arrive at Broca’s area to be articulated before language is produced.
Studies of Broca’s area
Since the discovery of Broca’s area being involved in language production, many studies have since found that this area may serve more functions than was previously believed.
For instance, it has now been recognized that Broca’s area may play an important role in the comprehension of language.
Cooke et al. (2002) used a neuroimaging method called functional magnetic resonance imaging (fMRI) on participants whilst they were presented with written sentences differing in their grammatical structure and short-term memory demands.
The researchers found significant activation in the brain region which corresponds to Broca’s area, when participants were comprehending the sentences.
In other studies, it has been suggested that Broca’s more can be activated during tasks that do not require producing actual speech (Gabrieli et al., 1998; Bookheimer et al., 1995).
In a study that used positron emission tomography (PET), it was found that there was greater blood flow in Broca’s area when participants read silently than when they read verbally.
This suggests that Broca’s area may have more of a role in the semantic processing for silent than verbal reading.
Otherwise, other studies have shown that Broca’s area has activated during the acquisition of grammatical rules, discrimination of speech sounds, and during the reproduction of rhythms (Bookheimer, 2002).
Similarly, this area is also thought to be active during movement and action (Nishitani, Schurmann, Amunts, & Hari, 2005), and during the imitation of movement (Nishitani & Hari, 2002).
Finally, Broca’s area is thought to contain mirror neurons, which are neurons which have been typically found in primates when observing and mimicking other’s behaviors.
Since mirror neurons have been found in Broca’s area, it could be suggested that this area also plays a role in being able to observe others’ movements during speech and imitating their speech.
History of Broca’s area
Paul Broca was a French physician who discovered what would later be named as Broca’ area. In 1861, Broca met a patient called Louis Victor Leborgne, who would also be known as ‘Tan’.
Broca found that Leborgne had difficulties with producing speech, often wanting to communicate his thoughts but being unable to. Leborgne was also known as ‘Tan’ since this was one of the only words that he could produce, often repeating the word twice, saying ‘Tan tan’.
Leborgne often used gestures to communicate to Broca, but sometimes became frustrated at his inability to express himself.
At the time, there was a lot of debate as to whether there were specific areas of the brain specialized for certain functions or if the entire brain was utilized for every function, known as a holistic viewpoint.
There was some evidence emerging that suggested that speech may be localized to the frontal lobes. Broca intended to investigate this further as he held the idea himself that brain functions may be specialized to certain areas.
When Leborgne died, Broca completed a post-mortem of his brain to investigate any abnormalities. As Broca lived in a time before modern neuroimaging techniques existed, one of the only methods of discovering brain differences at the time was to wait until patients had died to be able to view their brains.
During the brain examination, Broca discovered that there was a crater, he described as the size of a ‘chicken’s egg’, in Leborgne’s left frontal lobe. Broca concluded that the damage to this area was the root cause of Leborgne’s difficulties in producing language.
Although Broca’s case study seemed like solid evidence to support this view, he continued to look for other cases to prove his hypothesis further. Within a couple of years, Broca discovered eight cases of individuals who had problems producing language who also had damage to the same area.
With these individuals, he also noticed the damage was always in the left hemisphere.
This region of the brain became known as Broca’s area as a result. Damage to this language area is known as Broca’s aphasia. The main symptom of Broca’s aphasia is a deficit in the production of spoken and written language.
People with damage to this area would be unlikely to articulate words the way they would like to and being unable to string coherent sentences together.
Similarly, people with this condition may speak in an abnormal tone or rhythm, as well as having repetitive speech, disordered grammar, and a disordered structure of individual words.
As with the case of Leborgne, an individual with Broca’s aphasia may only be able to produce two words at a time, often repeating the same word.
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