Language Processing In The Human Brain

(Editor’s note: This article is from a past issue of Brain World magazine. If you enjoyed this article, please support us with a print or digital subscription!)

Brain

“My own brain is to me the most unaccountable of machinery — always buzzing, humming, soaring roaring diving, and then buried in mud. And why? What’s this passion for?” said Virginia Woolf, who was so talented at emulating consciousness and the duplicity of the human mind on the page.

Most writers forget that our brains have anything to do with the words we write, that writer’s block, passion and creativity are not solely the property of our suspicious unconscious. Arranging words in an artfully syntactical manner is but one aspect of language processing — the way human beings process speech or writing and understand it as language, which is made completely by and inside the brain.

So how do we humans process language? And how does that neural activity translate into the art of writing?

The History of Language Processing

Scientists have been studying the relationship of language and speech for nearly 150 years. In 1861, while Abraham Lincoln was penning his famous inauguration address, French neurologist Pierre Paul Broca was busy discovering the parts of the brain behind Lincoln’s speech — the parts that handle language processing, comprehension and speech production (along with controlling facial neurons).

What we now know as “Broca’s area” is located in the posterior inferior frontal gyrus. It’s where expressive language takes shape. Broca was the first person to associate the left hemisphere with language, which remains true for most of us today. (This can’t be said about every brain — it’s possible to have a language center on the right side, which is where the language loop lies in the brains of about 30 percent of left-handed people and approximately 10 percent of right-handers.)

Tucked in the back of Broca’s area is the Pars triangularis, which is implicated in the semantics of language. When you stop to think about something someone’s said — a line in a poem, a jargon-heavy sentence — this is the part of your brain doing the heavy work. Because Broca studied patients who had various speech deficiencies, he also gave his name to “Broca’s aphasia,” or expressive aphasia, where patients often have right-sided weakness or paralysis of the arm and leg due to lesions to the medial insular cortex. (Another of Broca’s patients was a scientist who, after surgery, was missing Broca’s area. Though the scientist suffered minor language impediments, such as the inability to form complex sentences, his speech eventually recovered — which implied some neuroplacticity in terms of where language processing can take place.)

Ten years after Broca’s discoveries, German neurologist Carl Wernicke found that damage to Broca’s area wasn’t the only place in the brain that could cause a language deficit. In the superior posterior temporal lobe, Wernicke’s area acts as the Broca’s area counterpart, handling receptive language, or language that we hear and process.

The arcuate fasciculus links Broca’s area to Wernicke’s area. If you damage this bundle of nerves you’ll find yourself having some trouble repeating what other people say.

Wernicke was also the first person to create a neurological model of language, mapping out various language processes in the brain — speech-to-comprehension, cognition-to-speech and writing-to-reading — a model that was updated in 1965 by Norman Geschwind. Much of modern neurology as it relates to language is modeled on the Wernicke-Geschwind model, although the model is somewhat outdated today — it gives a broad overview but contains some inaccuracies, including the idea that language processing happens in sequential order, rather than in various parts of the brain simultaneously, which is what know today.

In the 1960s, Geschwind discovered that the inferior parietal lobule has something important to do with language processing. Now, thanks to much improved imaging technology, we know there’s another route through which language travels between Broca’s area and Wernicke’s area in the inferior parietal lobule. This region of the brain is all about language acquisition and abstract use of language. This is where we collect and consider spoken and written words — not just understanding their meanings, but also how they sound and work grammatically. This part of the brain helps us classify things using auditory, visual and sensory stimuli; its late maturation might be why children usually don’t learn to read and write until they’re somewhere around the age of 5.

The fusiform gyrus is also in the frontal lobe, and also plays an interesting role in language processing in the brain. This area helps you recognize words and classify things within other categories. Damage to this part of the brain can cause difficulty in recognizing words on the page.

Today, we’re constantly learning new things about how language works. For example, we believe that the right brain performs its fair share of language functions, including the ability to comprehend metaphors as well as patterns of intonation and poetic meters.

Whereas we used to believe that people who speak with signs used a different, more visually dependent model of language processing in the brain, we now believe that language happens similarly in verbal and nonverbal ways. As it turns out, the brains of deaf people function much the same way as their hearing counterparts: The same parts of the brain are activated while speaking, whether that’s by using signs or not. This research was presented in a 2007 issue of NeuroImage, but this past February, Karen Emmorey, a professor of speech language at San Diego State University, presented new research at the American Association for the Advancement of Science in San Diego illustrating that the brain reacts to signs that are pantomimes — drinking, for example — in exactly the same way as if the word “drink” were spoken aloud.

“It suggests the brain is organized for language, not for speech,” Emmorey says.

Nouns and Verbs

How does the brain react when we use a verb like drink as opposed to a noun like milk?

New research shows that the brain actually treats nouns and verbs quite differently. Children typically learn nouns before verbs and adults typically react faster to nouns during cognitive tests, according to a February 2010 article in NeuroImage by Antoni Rodríguez-Fornells, an ICREA researcher at the Cognition and Brain Plasticity Unit of the University of Barcelona, along with psychologist Anna Mestres-Missé of the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, and neurologist Thomas F. Münte from the Otto-von-Guericke University Magdeburg, in Germany, in a study that illustrates how the brain functions when brains meet new nouns and verbs.

(Editor’s note: This article is from a past issue of Brain World magazine. If you enjoyed this article, please support us with a print or digital subscription!)

2 Comments

  1. Simple story.well written.planning to connect panini yoga computers and brain for language processing.looking for a lab and a fuultime research appointment

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