Broca’s and Wernicke’s areas in the left hemisphere.
People like boxes. Perhaps that’s why it’s still in textbooks, taught in colleges by neurologists, and displayed in anatomical museums: language resides in your left hemisphere, in two specific brain regions. Broca’s area is responsible for language production, and Wernicke’s area is for understanding language. Decades ago, brain researchers questioned this, but now they agree that things are different.
We need a large part of our brain to be able to talk and listen, to read and write, and to understand all of this properly. It is precisely all those different parts of language that make the process so complex. Ask Peter Hagoort, professor of cognitive neuroscience and director of the Donders Institute, how that works and his answer will be analyzed on the spot: “I now have an idea in my head that I want to tell you. I convert that into air vibrations through my mouth. They enter your ears and are converted into sounds, on which your brain gives them meaning. That whole process is language. Compare it to a car: it consists of wheels, windows, an engine, a steering wheel and so on. What is the car then? And how does it work? To understand that, you have to break it down into parts.”
A look under the hood soon makes it clear that language does not fit into a simple box. After all, when you talk, your brain controls countless muscles. That is quite different from picking up those sounds with your ears and thinking about what they mean. And we are only talking about spoken language here. “The brain is a network organization. Certain areas in the brain are certainly more important than others, but you can’t separate them. The connections between them are just as important. We now know that in language we use many areas and connections that are located on both the left and right sides of the brain.”
Connections in the brain involved in language. There is indeed a division of labor between brain regions. But the whole process of language production and processing involves a lot of regions. The connections between them are therefore just as important.
Stubborn left
Yet it appears to be a persistent view that language is only located in two specific areas on the left side of the brain, neuroscientist Vitória Piai (Radboud University) also notes. “I sometimes speak to neurologists who are surprised when I point this out to them.”
Piai studies how language works in the brain, in particular what happens when the brain is damaged, such as after a stroke. Many people then suffer from aphasia, a language disorder that can manifest itself in several ways. One patient has difficulty finding words, while another makes grammatical mistakes or has difficulty speaking. It just depends on where the brain is damaged.
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That alone supports the understanding that language is spread throughout the brain. This knowledge has a modest impact on the diagnosis of aphasia; little has changed in its treatment so far. Piai: “However sad, this insight does not have much influence on the treatment of aphasia. Attempts are being made to activate or suppress certain brain regions with non-invasive brain stimulation techniques, but unfortunately the results are not yet promising. We can now predict the consequences of brain damage better than in the past. If the corticospinal tract is affected – the connection between the motor part of your brain and your spinal cord – we can, for example, accurately predict which movement problems someone will develop. Although this is more difficult for aphasia than for the musculoskeletal system, we can also predict a little more about the severity and form of aphasia.”
Language therapy
The approach to aphasia is mainly in behavior rather than medical intervention. Marina Ruiter, aphasia researcher at Radboud University, notes that, just like 20 years ago, people look at what is most affected: speaking, listening, understanding, reading or writing. Practitioners then adjust language therapy accordingly. “There is more discussion about the consequences. Does therapy ensure that people use language in the same way as before the onset of brain injury? Or does the improvement in language use point to a different way of communicating?”
In some cases that is obvious. For example, people with aphasia often point to something rather than say what they mean. Ruiter: “But it can also be subtle, for example if people with aphasia deliberately avoid abstract and low-frequency words or make their sentences slightly less grammatically complex. Changing behavior is much more complex than true recovery. This requires the suppression of old habits and the use of other cognitive functions. Most people with aphasia do not fully recover, so they still have to find a way to adapt. Therapy for this is complex, so we have to handle it carefully. If people with aphasia have to do difficult language exercises for too long, we see that this can have adverse consequences, such as mood complaints, less effective treatment and higher healthcare costs.”
Language as network
Where language is located in the brain is also a fundamental question. The answer to this may ultimately have an impact on helping patients, but according to Peter Hagoort there is still a lot to learn about healthy people. “We have relatively little insight into that. There are many differences in the language skills of people where everything works well. What determines those individual differences? Those variations are important, because you could, for example, adjust teaching methods accordingly.”
The brain consists of different regions. Each with a certain specialization, but it is not absolute. For higher cognitive functions, they have to work together a lot.
Roeland Segeren, via Envato
Roeland Segeren, via Envato
In that kind of language research, it is important to look beyond specific brain areas. They are indeed important, but part of a network. Think of that car: if you don’t know what the brakes do, you don’t understand why there are brake cables. For example, language researchers look at nerve pathways. “There are really big differences between people. The wiring in the brain can be thicker, more or less symmetrical. By comparing those differences to language skills, you can discover which biological differences are important.”
Hagoort emphasizes that it is important to realize that brain regions are more flexible than previously thought. “There is definitely a division of labour. Depending on what comes in and how the cabling runs, a certain specialization is created. But it is never absolute. Visual information is received in the visual cortex at the back of the brain. But if you switch off that input, it will do something else. In blind people, for example, you see that this part of the brain can play a role in language processing.”
In any case, the classic division of the brain into boxes serves a didactic purpose: it is easy to explain it that way. Hagoort therefore expects that it could take years before this is reflected in textbooks. “I still see it in biology textbooks. You can’t just get that out. Next year I will retire. The first thing I will do is write a book in which it is clear and correct.”