Wednesday, 18 November 2015

The Lowdown on Language – Aphasia and your Brain

Language is something that we often take for granted, but it is at the core of what makes humans such an impressive species. Right this second, as you are reading this sentence, your brain is seamlessly recognizing the squiggles that form the letters, linking the squiggles together to form sounds in your head, connecting the sounds to form words, and connecting the words to let you know what the message is that I’m trying to communicate. And you can somehow manage to do all that while simultaneously eating a sandwich. Humans are masters of language.


In addition to allowing us to communicate complex messages across impossible spans of time, language is responsible for another great human achievement: understanding that different parts of our brains do different things. It may seem obvious, but for a very long time, we didn’t have the faintest clue what was going on up there.

The thing about people with difficulties in how they understand and produce language is that, compared to people with other neuronal deviations, they are easy to study. First of all, language impairment is obvious. Whereas a problem like face-blindness or colour-blindness can go unrecognized for a person’s entire life (researchers estimate that as many as 2% to 2.5% of people could be prosopagnosic, or face-blind, to some degree), language is something we notice more quickly because we rely so much on verbal communication. Second, language impairment frequently leaves unaffected the areas of the brain that control behaviour, intelligence, and curiosity. The upshot is that you have otherwise normal (or in some cases brilliant) people who just aren’t able to talk, read, or write as easily as others.


Back in the early 19th century, when scientists were still scratching their heads about the way our heads worked, having cooperative patients was a huge advantage. That is likely the reason that language was one of the first systems to be identified in a somewhat useful way. As early as 1825, a Frenchman by the name of Jean Baptiste Bouillaud predicted that language function would be located in the left-hand side of the frontal lobes of the brain.

In 1861, Bouillaud’s own son-in-law, Ernest Auburtin, was working with a patient with an exposed frontal lobe (if that sounds gross to you, don’t read our story about Phineas Gage) and noticed that when pressure was applied to that part of the brain, the patient lost the ability to speak. Auburtin predicted that after the patient died he would find a lesion on the left frontal lobe. Unfortunately for Auburtin, his patient was of hearty stock and lived to see another researcher by the name of Paul Broca prove Auburtin’s prediction correct. Subsequently, and pretty unfairly, the speech area that was discovered is now called Broca’s area.

Dysfunction in Broca’s area produces what is called non-fluent aphasia, meaning that a person has a tough time retrieving and producing words. This does not mean the words are not in the person’s head, just that there is a problem with the connections that move them from memory to the mouth or pen. What is really curious is that verbs and the use the grammar suffer the most.


Deeper research into language also revealed the brain area humans use to understand words. Named for its discoverer, Carl Wernicke, Wernicke’s area is located in the left temporal lobe of the brain (behind your temple) and directly connects to Broca’s area. Wernicke’s area helps us understand the sounds of speech, and its function can be built up or lost depending on a person’s environment. For example, people who grow up speaking Japanese often lose the ability to distinguish between the sounds made by “L” and “R”, since their language doesn’t require them to and their brain is out of practice.


The other function of Wernicke’s area is in producing speech, but where people with difficulties in Broca’s area have a hard time producing sounds and words, people with problems in Wernicke’s area talk a lot. The problem is, what they say makes no sense. It is a string of nonsense that researchers call “word salad.”

Problems with language, or aphasias, come in all shapes and sizes, to the extent that a person dealing with aphasia can almost seem like they are faking it. For example, researchers Bryan Kolb and Ian Q. Wishaw describe a patient in their book Fundamentals of Human Neuropsychology, who suffered from anomic aphasia, meaning that he could not retrieve the names of objects. When shown a picture of a ship’s anchor and asked what it was, he couldn’t name the item but replied, “I know what it does… you use it to anchor a ship.” The patient could use the word as a verb, but not as a noun.


The take home message here is that no brain is perfect. Some of us have a hard time with sports, others can’t cook, some people are quick to feel sad or angry, and others struggle with language. It is up to each of us to show the world the things we’re good at, while trying to improve on the things we’re not… At least until we can repair our brains with nano-bots and everyone is as smart as Da Vinci.

Reference:

Kolb, B & Wishaw, I.Q. (2009) Fundamentals of Human Neuropsychology. Worth Publishers. New York, NY, U.S.A.

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