Left Versus Right: How Brain Injuries Impact Language Processing

Strangely, injuries to the brain aren’t symmetrical in regard to the body

By Peter M. Vishton, PhDWilliam & Mary
Edited by Kate Findley and proofread by Angela Shoemaker, Wondrium Daily

Did you know that one area of our brain is responsible for creating the words that we speak while another area helps us to understand others’ words? When it comes to brain injuries, left-handed and right-handed people are impacted differently. Professor Vishton explains.

Close up of brain scans
Separate areas of the brain control language processing abilities. Left-handed and right-handed people experience brain injuries differently. Photo By Triff / Shutterstock

Language Processing and Broca’s Area

Much research has been done on the systems of the brain that control language processing. Most of these studies revolve around the idea that separate areas of the brain are involved in distinct activities, such as talking, writing, listening, or reading. Two areas of the brain seem especially important for language processing.

Production of language takes place in Broca’s area—named for its discoverer, Pierre Paul Broca. He worked with patients who could no longer talk after suffering a brain injury. Based on careful work with these patients, however, he found that they could still understand spoken and written language just fine. 

As long as their responses were restricted to simple yes and no answers, they seemed almost completely unimpaired. This critical area of the brain is located in the frontal lobe, just behind the prefrontal cortex.

In addition to research on patients with damage to the Broca’s area, neuroimaging studies have confirmed the region’s importance for language production. When participants engage in language production—or even thoughts about language production without any actual speaking—this segment of the cortex becomes active. Having a thought and then translating that thought into a sequence of words is accomplished by Broca’s area.

Right-Handed Versus Left-Handed

Whether you are right-handed or left-handed affects how your brain is organized for language production. Most people prefer to use their right hand when they perform challenging motor activities—everything from writing to throwing a ball. 

For right-handed people, language processing causes a large increase in activity in Broca’s area in the left hemisphere of the cortex. Usually, only a small increase in activity occurs in the right hemisphere. 

For people who are right-handed, damage to the right side of the brain rarely results in language deficits. Damage to the left side is far more likely to produce these problems. For right-handers, it can be said that language production is lateralized, with a specialization localized in the left hemisphere.

Left-handed people are a little more complicated in this regard. One might presume that the organization would be reversed. 

Perhaps lefties would exhibit language dominance on the right side. In fact, though, most lefties show a more equal activation across the two hemispheres. The Broca’s areas of both hemispheres seem to participate equally in language production.

Injury Impact on Language Comprehension

What about language comprehension, though? Carl Wernicke, like Broca, worked with brain injured patients. 

He found that damage near the back of the temporal lobe often produced a loss of the ability to understand language—either written or spoken. Interestingly, these patients seemed to fully retain their ability to produce language. 

This area has come to be known as Wernicke’s area. Neuroimaging studies have shown that the same lateralization of function associated with Broca’s area is present. 

Right-handers tend to show strong activation in the left hemisphere when engaged in comprehension. Lefties show a more balanced pattern of activation.

When you hear or read a series of words, your brain translates these words into a set of ideas you will understand and remember. You can relate that idea to other things you already know. 

That translation process—from words to thoughts—is accomplished by Wernicke’s area. If you describe these ideas to someone else, Broca’s area will produce those words for you.

Far Apart but Interconnected

Language production and comprehension are implemented by these two different brain regions. Given the close relation between speaking and listening to language, it is surprising how far apart the two regions are. Speech production is accomplished by Broca’s area near the front of the brain, while language comprehension is accomplished by Wernicke’s area near the back.

Specifically, Broca’s area is located near the motor cortex in the frontal lobes. The motor cortex is involved in controlling voluntary movements, including those that produce speech. 

Wernicke’s area is located very close to the auditory cortex, a region of the brain devoted to processing incoming sounds. For understanding spoken words, that location seems to make sense.

Even though the two regions are located relatively far away from one another in the brain, they are highly interconnected—both with one another and with other parts of the brain. Tomorrow’s article will delve into how these regions work together to develop our enormous internal lexicon.

Image of Professor Peter Vishton

Peter M. Vishton is an Associate Professor of Psychology at William & Mary. He earned his PhD in Psychology and Cognitive Science from Cornell University. Before joining the faculty of William & Mary, he taught at Northwestern University and served as the program director for developmental and learning sciences at the National Science Foundation.

This article was edited by Kate Findley, Writer for Wondrium Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for Wondrium Daily.