Broca’s area: Journeys to the Brain-11

Paul Broca:

Source: Wellcome Collection

under the license of CC BY 4.0

Broca’s area plays a very important role in our speech.

Prior to 1861, scientists debated whether the whole brain acted either as a single entity or contains specific regions. Pierre Paul Broca ended this debate in 1861.

“Monsieur Tan”

Prior to 1861, Pierre Paul Broca examined an adult male – Leborgne – who came with a right-sided paralysis.

Pierre Paul Broca was a surgeon who had a special interest in physical anthropology. He had been studying the association between skull shapes and sizes with evolution.

In addition to the Leborgne’s – Broca’s patient – right-sided paralysis, he was suffering from another problem. He produced only one sound with one syllable – “tan”, twice in succession. He was ok with understanding. Since then, the hospital staff identified him as “Monsieur tan”. Paul suspected Leborgne’s problem was due to some damage to the brain’s left side/ After his death, Paul dissected his brain and discovered a damaged region in Leborgne’s brain’s lower part of the left Frontal lobe. You can read more about this in Broca’s region article.

Broca found a similar lesion at the same place in his second patient’s brain too – “Lelong” who had a stroke and spoke only five words.

In 1861, Paul Broca presented his findings – “our brain owns a specific area in charge of speech production” – to the world.

Three years later, Broca described 25 similar cases. All but one had a damaged area at the same place in the brain: lower part of the left Frontal lobe – just above the left eye’s orbit.

With that, he ended the great debate at that time: “the brain owns specialized areas for specific functions”.

However, now, we know that this is not 100% accurate.

Broca’s area

File:Broca's area - lateral view.png

Broca’s area

Source: Polygon data were generated by Database Center for Life Science(DBCLS)[2] under the license of CC BY-SA 2.1JP through Wikimedia Commons

Since then, the medical community has continued to name this area in the left hemisphere as the “Broca’s area” to recognize his exemplary work. And, the inability to produce speech as a result of damage to this area is named as “Broca’s Aphasia”.

Brodmann 44 and 45

Much later, in 1909, another expert – Brodmann – identified two parts of Broca’s area. These parts were named Brodmann 44 and 45 which are depicted in the following sketch.

Broca’s area: Broadmann 44 and 45: Wikimedia Commons

The most recent research has shown the Brodmann 45 is more active in meaningful language processing together with area 44. Moreover, it also has shown that its surrounding areas become active in more general domain-specific cognitive functions.

The Broca’s area rests on the lower part of the left Frontal lobe. I invite you to re-visit the Journeys to the brain: 2 – A walk over the brain surface which introduces different lobes of the brain. For easy reference, I have included a graphic that appeared in my earlier journey to the brain:2.

Brain lobes: Image source: University of Utah: https://library.med.utah.edu/kw/hyperbrain/figures/2a.jpg;
licensed under the creative commons: https://creativecommons.org/licenses/by-nc/2.5/

However, most recently, researchers, using sophisticated MRI technology, showed that Leborgne’s brain damage had gone beyond what we now have typically known as Broca’s area. This fact raised to doubt the exact role of Broca’s area in speech production.

Using the latest technological advancement, researchers have shown that Broca’s area mediates the interaction between the Temporal lobe which helps us to process listening, and the motor area of the Frontal lobe, the area sends signals to speak.

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Author: Prasantha De Silva

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