Mystery patient solves mystery of the brain

The discovery of Broca’s area in the brain was a major leap in the world of science, shifting the paradigm to the way we study the brain today. Broca’s area is the area in the brain that controls the motor movements to produce speech. In contrast, Wernicke’s area is the area responsible for understanding and analyzing speech.

Pierre Paul Broca is the one credited with discovering the localized areal of the brain the produces language. However, he wasn’t the first one to come up with the idea. It was actually the founder of phrenology, Franz Joseph Gall, that first believed the area of the brain that produced speech was located in the anterior lobes. Phrenology is a pseudoscience where the bumps on the skull were felt to determine one’s personality traits or intelligence.

If you think about it, the brain named its self. Photo from Creative Commons.

Many in the science world were skeptical because of the case of Phineas Gage. Gage was a railroad worker who had an accident involving a tamping iron penetrating his skull and causing severe frontal lobe damage. Despite the damage, Gage was able to maintain his ability to speak.

It wasn’t until Ernest Aubertin presented his data associating the inability to speak (also known as aphasia) and frontal lobes that Broca and other members of the science community became interested in the theory of a region in the brain localized to speech. Aubertin was so confident that aphasia was somehow caused by frontal lobe damage, he offered 500 francs to anyone who could find an aphasic patient without frontal lobe damage and that he would renounce his views if such a patient was found.

Broca accepted the challenge and that was when he met his first aphasic patient Monsieur Louis Leborgne, or “Tan” as he was known at the time because it was the only word he could say.  Leborgne was a craftsman and a church keeper who was epileptic as a child. He was hospitalized when he lost his ability to speak. Some historians say it was syphilis that caused the damage to the brain that enabled him to speak.

While in the hospital, his condition severely worsened. The damage to his brain had caused right-sided paralysis so he was bed-ridden. He was also undergoing surgery for gangrene. He was on his death bed when he met Broca and died six days later.

Broca immediately did an autopsy and discovered damage to the left hemisphere of the frontal lobe. Gall’s and Aubertin’s theory, it seemed, had been correct. This finding was important because it was the solid proof of localization of brain functions. Broca began studying other aphasic patients and found similar results: a lesion on the left hemisphere of the frontal lobe.

Broca became an avid supporter of the localization of function in the brain but emphasized that his theory was different from those of phrenologists. In response to the strange case of Phineas Gage, Broca theorized that for right-handed people the localization of speech in the brain was often in the left-hemisphere, while for left-handed people, which are the minority, localization of speech could sometimes reside in the right-hemisphere. He also theorized that if damage had occurred in the left hemisphere at an early age, the localization of speech could develop in the right-hemisphere using neuronal plasticity.

The evidence of local areas of the brain governing function was an important discovery because at the time it was widely believed that both sides of an organ do the same things, such as the two lungs and two kidneys. The two hemispheres of the brain should be no different. After the discovery, it opened up a possibility that the two hemispheres can do different functions.