Brains and language, Apuntes de Psicolingüística

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Theme 2:

Brains and

Language

1. THINKING ABOUT THE BRAIN: A QUICK HISTORY

Western medicine took many centuries to figure out that the brain is used for thinking with ideas, dreams, and feelings. Our brains make it possible for us to use language to hear, speak, sign, read, write, and understand. Our brains make it possible for us to use language to hear, speak, sign, read, write, and understand. The ancient Egyptians gave us the first written document. the Egyptians still thought it was the heart and not the brain that controlled our ability to think and move our bodies. About two centuries later, Hippocrates and his colleagues finally got it right. Franz Joseph Gall started a theory known as PHRENOLOGY. They claimed that they had found brain areas for things like mirth and self-esteem, all based on feeling the bumps on people’s heads where the enlarged brain was supposedly pushing the skull outward. Though phrenology sounds preposterous today and was later discounted, Gall still gave us the idea that different areas of the cortex might specialize in different functions.

FIGURE 2–1. A phrenology bust shown in an advertisement for the Phrenological Journal from

1848. Note that language is located near the eye (marked as “lang”) and is shown here on the right side of the head.

LOCALIZATION OF FUNCTION , is still valid for some of our abilities, ut, before we continue with our story of how the brain processes language, we need to know a little about how the brain works. Information processing, including language processing, begins at the level of individual brain cells, and how they interact.

2. WHAT DOES IT MEAN TO SAY THAT THE BRAIN PROCESSES INFORMATION?

“Processing information” is a phrase that immediately builds a wrong subconscious image. This image makes us think of some kind of food processor or bread-making device. Not good. Try

3. HOW CAN A BUNCH OF CELLS LEARN OR KNOW SOMETHING?

All those neurons are sending information to one another. If information (someone’s name, the taste of a particular kind of cheese, as much as you can recall of a gorgeous sunset, etc.) or a skill (how to tie a bow, how to parallel park a car, etc.) is going to stay in your brain, it must change your brain a little. : Every experience, conscious or unconscious, makes tiny changes in the strengths of the synaptic connections between some of your neurons; that is, it changes how many bunches of neurotransmitter molecules will be sent from a neuron to its neighbour if the first neuron becomes active. You’ve got billions of connections, so small changes in a few of them don’t destabilize your brain and make you lose what you’ve already stored. But those small changes do modify what’s there. When you learn a word, its sound, meaning, and the grammatical and social contexts for its use, as well as the voice of the person who said it or the look of the page where you read it, all get linked up to other information of the same kinds, as well as staying linked to each other. The idea that the brain keeps changing with experience as synaptic connections change strength is called brain PLASTICITY. Brains are much more plastic than we used to think. For example, in deaf people, neurons that would have been used for sound perception are used for processing visual language, and in blind people, the area for processing sounds expands into the area that normally processes vision possible, and more use of language.

So your brain’s knowledge exists, at least in large measure, as an enormous set of synaptic connection strengths. And these connections mean something because they are ultimately linked to parts of the brain that are tightly connected to SENSORY NEURONS and MOTOR NEURONS. When you remember how something looks, sounds, or feels, you are picking up a small part of the sensory activation caused by the original experience. If the memory is not quite true to the original event—and memories can be modified by time, emotions, and later experience—it’s because the synaptic connections that stored the original information have been changed.. What activates them is your wanting (or being prompted) to do this thing, plus your memory of having done this thing before. The memory of all the times you have said your name or broken an egg into a bowl has been formed from signals that came back to your brain from your mouth and your ears, or your hands and your eyes, as you learned to do these highly skilled acts. Some of these were sensory signals that became linked to the motor signals you had just sent out. When these links between intention and all the motor and sensory memories are weak or missing, a person’s intentions are cut off from his or her ability to carry them out. Strokes and other brain injuries can cause this kind of disconnection in a brain, but another way we get weak links is more familiar. People who are taught to say a phrase in the clinic or classroom, often fail to use that phrase when they need it in the real world. Because the memory of how to say the phrase is too strongly linked to the room where it was learned and the need to satisfy the teacher, and barely—if at all—linked to the situation where it will really be needed.

Imaginative teaching techniques are needed to help beginning students or disabled clients form strong and usable links between language and what they will need to use language for.

4. ACTIVATION AND ITS SPREAD

Having a strong link between your intentions and your stored motor and sensory memory is important if you want to do something without the help of the context. This is true whether it’s something you learned to do in the real world and now have to perform in some kind of test, or whether it’s something you learned in a class and now have to use for real. When some of the many stages of linkage between intention and stored motor memory are damaged or broken, as in some types of brain injury, people may have one kind of APRAXIA , the inability to carry out an action even though they understand what they are supposed to do and have no paralysis of the muscles they would need to do it with.

To understand this paradox, we need to explore further two of the most important concepts in this book: the concept of the ACTIVATION of a neuron or group of neurons, and an understanding of SPREADING ACTIVATION (i.e., how activation spreads from one group of neurons to other groups).

ACTIVATING a neuron means building up chemical changes inside it to the point where it starts sending out signals to the other neurons that it is connected to. Each neuron has a RESTING LEVEL , where it stays when it is getting only a few neurotransmitters stimulating the synapses of its dendrites to pass electrical signals toward the CELL BODY. But when enough neurotransmitters from active neighbor neurons barge into the dendrites of the sleepy neuron at about the same time, the resulting barrage of electrical signals starts to wake it up, to AROUSE it.

Different areas of the brain are specialized for handling different kinds of information, so activation must spread over long-distance networks, not just between neighbors, using major pathways between the brain regions. As children learn and develop, these pathways become more and more efficient highways for neural electrical activity. Brain coordination that we need to deal with the huge amount of information that keeps bombarding us all the time we are awake. Children with developmental problems like autism seem to have poorer long-distance brain coordination, but we are a long way from knowing whether that is a cause or only a symptom of their information processing problems.

4.1. REAL-WORLD LEARNING: ESTABLISHING MULTIMODAL CONNECTIONS

Clearly, our brains are not particularly selective. All the things that are going on at a given instant are linked together (and as we get older, we seem to hold onto more and more of this incidental information, which can compensate for some of the memory problems that come with aging). The links are usually weak at first, but if an event arouses strong emotions, strong ones may be forged immediately, probably by a rush of additional neurotransmitters at the synapses. There’s a good reason for our brains to work in such an indiscriminate way. Learners (including animals other than humans, of course) can’t know from the beginning exactly what about an experience is going to end up being important.

When two sets of stimuli occur together many times (think of all the motor and sense impressions you get each time you eat an apple, open a package, or start up your computer), the connections among them get strengthened, but one-time links, unless they were associated with a strong emotion, get swamped by the ones that are growing stronger, and become unable to contribute to remembering anything.

Figure 2–5. A view of the left side of the brain. Extra-deep grooves, called sulci, divide the outer layer (cortex) into four lobes. Image adapted from Shutterstock. All rights reserved.

Figure 2–6. Major divisions and primary areas within each lobe, shown on the left side of the brain.

Some of the language areas are located very near these primary motor and sensory functions. Brain regions that are important for speech lie next to the motor areas for moving the lips, tongue, and jaw. Regions important for the comprehension of speech sounds can be found near the primary areas for hearing. It makes us wonder whether language evolved out of these basic functions or whether this is just coincidence.

4.3. LEARNING FROM APHASIA: EARLY STUDIES OF LANGUAGE LOCALIZATION

For years, the gold standard for determining the regions of the brain important for language was to observe the deficits that occurred in a person who had sustained a brain injury. Suppose we assume, that different parts of the brain have different jobs to do. Then the logic of LOCALIZATION goes something like this: If you lose a particular language function after injury to a specific area of the brain, then that area must be necessary for that function.

Maybe it is —but maybe it’s only one of many parts that are essential to that function. And maybe it does other things, too.

Observations of language deficits after brain injury are made by studying the language problems of people with APHASIA , best defined as a language disorder that occurs after injury to a part of the brain. There are several different types of aphasia and all of these have been described in relation to their behavioural profiles (what a person with that kind of aphasia can and can’t do with language) as well as the brain areas that have been affected.

The best-documented of these brain-language relationships was published by a surgeon named Pierre Paul Broca over a century and a half ago in Paris. Broca was left with the impression that his patient could understand most of what was said to him but could not express his responses, and hence had lost only his ability for “articulate speech.” Broca came to believe that it must be the left frontal lobe that was important for speech, at least in right-handed people. (Recall that the left side of the brain controls the right side of the body.) Thus, Broca theorized not only the localization of this function but its LATERALIZATION —its position on just one side of the brain. Though there were many subsequent debates regarding the accuracy of Broca’s conclusion, the area in the left inferior frontal gyrus described by Broca became known as BROCA’S AREA and the aphasia he observed as BROCA’S APHASIA. A decade later, a young physician named Carl Wernicke published a complementary finding regarding a different type of aphasia that he had observed. Wernicke described a patient who could produce speech without difficulty, but who could not understand the language he heard. Wernicke also described an elaborate localizationist theory—that is, a theory of how different brain regions might support different components of language.

After several decades of other non-localizationist models, Wernicke’s theory was reborn in 1965, through the writings of the neurologist Norman Geschwind. Most patients with Broca’s aphasia do have lesions in the left frontal lobe and those with Wernicke’s aphasia, in the temporal lobe. In particular, Geschwind revitalized the notion of DISCONNECTION SYNDROMES , in which damage to fiber pathways can cause disturbances in language even though key areas of the brain are not damaged.

neurons to other neurons. Those neurons can be in the same lobe or different ones, but all together they make up a large language network.

different pieces of the process happen in many different cortical areas, sometimes in serial and sometimes in parallel, connected by an organized set of axons that combine together to make up the language network. If we think back to our cities-and-roads analogy again and conjure up a mental image of a local city neighbourhood with its own side streets, we can compare that to a small cluster of neurons connected by short axons. They each have their own little network with like-minded activities. Tie a group of these neighbourhood networks together with roads (longer axons) and you get a city, perhaps one with its own certain specialty (e.g., producing chocolate, making movies, coordinating articulatory movements!). Those cities work together to form states and countries (mini-networks) that also work together and thus are able to accomplish far more than the neighbourhoods alone.

Neurons work together to form growing networks that work well individually, but combined together, can achieve more complex functions.

2.7 Functional connectivity The brain areas that work together.

We talked about how brain areas “wire” together. But they don’t just connect to each other randomly. Presumably they wire together so they can “fire” together so that those axons from one part of the brain can pass on information to the neurons in other parts of the brain.

One result of this new work with resting state networks is that there appear to be regions of the brain that function as “hubs”; that is, they are key nodes of a network because they have more connections than other nodes do. Moreover, some of these hubs are particularly well connected to hubs of other networks, whose job may be to facilitate the integration of information from one network to another.

2.8 Does the right side of the brain participate in language?

It’s not just the left side of the brain that supports language. The right side also plays an important role. People who have suffered a right hemisphere stroke or brain injury often have difficulty understanding the linguistic nuances that make jokes funny. They may take everything literally, or have trouble understanding metaphors or interpreting the emotional contours that can alter the meaning of the sentence. These are not deficits in finding words or putting together sentences, but they do impede the process of communication. They are deficits in PRAGMATICS. Pragmatics includes things like using the right intonation to indicate a question or an exclamation, making eye contact when you’re talking with someone, refraining from saying things that are inappropriate in certain circumstances, and letting others share in the conversation. People with aphasia after left hemisphere injury rarely have problems with pragmatics; even though they struggle with getting the words to come out the way they want. People with right hemisphere injury usually speak easily and fluently, but their pragmatic deficits can affect their social communication skills, sometimes even alienating friends and family members.

2.9 Top-down and bottom-up processing: our brains are constantly integrating predicted and new information

Below the level of consciousness, our minds and our bodies are constantly working to deal with information about our surroundings. External and internal sensations bombard us, endless. The enormous bulk of these sensory data has to be kept from driving us crazy so that we can

concentrate on what we want to. But when background information becomes important — an unfamiliar voice in the next room, a fire siren in the distance, a stone in your shoe — it has to get through so that we can respond appropriately. So the brain mechanisms that focus us on the traffic or on the page we’re trying to read have to be screening devices, not shut-off devices.

Our brains have several ways of managing to keep bulk information under control; the most important one for language (and many other areas of information) is prediction , based on activation spreading from one neuron to another along pathways that have become strengthened in the course of learning. A major part of becoming a skilled language user is learning what sounds and words are likely or unlikely to be what you hear or see in the next instant of listening or reading. This is what it really means to be learning the patterns of your language.

2.9.1 Language pattern.

Suppose you are a native speaker of English, you are at a bus stop with a good friend, and a truck roars by just as she starts to say, without any particular context, Hey, why don’t you come over for dinner tomorrow? All you actually hear might be something rather like Hey, ay (something something something) Yet the chances are that if you heard this barely intelligible sentence, you would understand what your friend said, and be able to answer her appropriately as soon as she got to the end of it. On the other hand, if you have had only about a year of some other language, you’d probably have to ask the speaker to repeat what she had said, even if you know all the individual words.

Why is there a difference between your ability to understand a sentence through noise in a language that you know natively and one that you don’t know well. The answer lies in the enormous amount of unconscious knowledge of English you have been accumulating since three months before you were born. You now carry in your head information about what speech sounds exist in English, which ones are likely to occur at the beginnings of clauses or next to certain others, and which ones are easily drowned out by noise. You know, unconsciously, which words are more frequent than others, which ones are likely to occur in a particular grammatical and social context, which ones are likely to be stressed, and which words or parts of words will have to occur if certain others occur. For written words, we also have the same kind of unconscious knowledge of possible letter sequences, so that we can find words in “visual noise.” To give yourself a sense of how strong this unconscious knowledge is, for written English anyway, try quickly reading the text in the following paragraph while spotting all seven errors:

TOP-DOWN language processing. The “top” is your expectation of what should be there, and the “bottom” is what is in fact on the page or in the sound waves. A non-native speaker with a really good knowledge of English may actually do better at spotting some kinds of proofreader’s errors, because she must rely more on the “bottom” — that is, on the information that is actually on the page. If you are less able to rely on top-down processing, you must rely more on BOTTOM-UP processing — on the letters on the page, or the sound waves hitting your eardrum. How does top-down processing of language work? It relies on subconscious knowledge of many kinds and we can illustrate a few of them here. we have very good subconscious knowledge of the frequencies of words, and whether they are likely to occur in particular contexts. Knowing which ones are probable in a particular grammatical context is also linguistic knowledge, but knowing which ones are likely to occur between good friends at a bus stop with no more context than Hey is part of our social knowledge.

2.9.2 How we learn language patterns.

How do we learn phonotactics, phonology, morphology, syntax, and the many levels of pragmatics that we touched on in Chapter 1? There has been intense controversy for many years between those who think that much knowledge of possible linguistic patterns is built into human minds genetically — so that what children need to do is figure out which of those patterns are used in the language around them — and those who think that what is built into our