Can we now say that no single part of the brain that is specific for language? What are the main parts, and what are the other functions that they serve? This vision is, of course, adopted by Elizabeth Bates, which you mentioned multiple times. This will help someone understand this idea well, that this part is doing one thing while simultaneously performing another function related to language.

Well, first of all, when I was looking at your website, I noticed that you had a picture of Liz Bates on the cover of one of your magazines, and I was extremely impressed. I think Liz Bates was ahead of her time in terms of thinking about language in the brain, and she is a huge influence on me. So, I thought that was very cool, and I’m glad your readers are going to get to read about this brilliant woman.

So, the idea of the quote, that language is a new machine built out of old parts, that’s such a great little quote. You know, those old parts are genetic; they are genetically specified parts. It’s not like the parts that you have to assemble, like finding over development. You’re born with the parts. If you have a human brain, you’re born with the parts that will be useful for language. And then, through experience and plasticity, you then connect those parts to create a language brain. So, you wire up the system, but the parts are in place.

So, your question was, well, what are those parts, and if they’re not designed for language evolutionarily and they get co-opted for different language, what are they doing? Well, there’s a lot of them. And if you haven’t recommended to your readers yet, the paper I would recommend is a classic paper by Greg Hickok and David Popple, a 2007 paper called ‘The Cortical Organization of Speech Processing.’ It’s in the journal Nature, and they make the case of a very elegant network.

I’m not going to try to do it justice in the short time I have, but a couple of key pieces. So, the left and right hemispheres, that’s the first notable feature. It’s not all left lateralized; it’s not all in the left hemisphere. It involves some of the major players. So, I mentioned Broca’s area, which is in the frontal lobe. It also involves an area in the superior temporal lobe; we call it Wernicke’s area. But there are all sorts of superior temporal gyrus, depending on what kind of language you’re speaking. But these are terms that most people who are familiar with language have heard of.

Those are two main hubs for two pathways of language. In the book, I talked about this dorsal pathway and a ventral pathway. Dorsal just means towards the top of the head; ventral just means towards the bottom of the head or the brain. And there’s a pathway right on you. Here, by right now, as I’m speaking, these words are hitting your eardrum, sending vibrations through your cochlea, and then down the auditory nerve to your auditory cortex. And that’s the point of departure, at least for spoken language.

Your auditory cortex sends the signal backwards towards this Broca’s and Wernicke’s area, and it’s there where you start separating functions. So, at a very basic level, one pathway goes ventral, and the bottom side of your brain starts to map those sounds onto meaning. So, it starts just like, first, it starts, you know, what are the phonemes I’m even hearing? And then, how do these phonemes combine into words? And what do these words mean? And then, how do these words combine into a sentence? And it starts processing the meaning.

But then this dorsal pathway, the one that goes towards the top of your head, this surprises some people, it starts to actually map those sounds onto motor outputs. And so, the way, what it’s actually doing is, when you’re hearing the speech, you are simulating the production of the speech yourself in your dorsal pathway. Motor construction is one way to understand by doing. You may have heard of mirror neurons, the way you comprehend someone’s reaching behavior by simulating those same actions in your brain. Researchers believe you’re doing that to some extent when hearing language, and it happens so rapidly. This is why speaking a second language is challenging; you lack the motor skills. It’s akin to a baby attempting to babble; you can’t process it fully. So, there’s a breakdown in this dorsal pathway.

These pathways meet in Broca’s area in the frontal part of your brain, which some have called the unification site, where it combines meaning and motor movements. That’s when you can put it all together. That’s the basic pathway. The really cool thing about that pathway is it’s not a one-directional street; you’re constantly traversing this pathway and then sending signals backward along the dorsal and ventral routes to predict what’s coming next. Anytime you hear language, you’re trying to predict the next word or what’s at the end of the sentence to aid comprehension.

All of this occurs predominantly in the left hemisphere, while the right hemisphere analyzes different aspects of the system, like prosody and connections between words over larger spans. Together, this network helps assemble meaning on the fly. As you build meaning, it becomes easier to understand new concepts. That’s why words at the end of sentences are easier to grasp than those at the beginning; more context has been built up.

This network involves brain regions responsible for various functions, not just language. For instance, mirror neurons in Broca’s area (or the inferior frontal gyrus) are also involved in understanding reaching behavior. When someone reaches for an object, Broca’s area simulates that action. We believe this language pathway hijacked or piggybacked on top of evolutionarily ancient systems like reaching behaviors, repurposing them for this new function. This is just one example of how language is built upon an old machine part, which originally served functions like grasping for hands.

Reference:

Hickok, Gregory, and David Poeppel. “The cortical organization of speech processing.” Nature reviews neuroscience 8.5 (2007): 393-402.

This post is part of multiple topics about “Language and the Mind”, a podcast that has been published in Real Sciences with Spencer Kelly the co-director of Colgate’s Center for Language and Brain in Colgate University.

Link to Language and the mind: https://www.amazon.co.uk/Language-and-the-Mind/dp/B085SZ9PSZ