DSRF Note:
Is speech and language an issue that needs medical research?

Children with Down syndrome have great difficulties with speech and language.
They pronounce words incorrectly a great deal of the time and cant seem to hear some sounds at all.

We know that many of our children have hearing problems as babies and as infants. Glue ear is very common and this makes the eardrum immobile.

So is it possible that when our children were babies they never developed that special area of their brain where the sounds of language are stored?

Without the specific sound information in memory that characterises our language they will find it very difficult to distinguish the difference between some words and they may never learn language correctly. To speak like a native you have to be able to detect tonal differences and sound emphasis peculiar to the language. Imagine trying to do this if you had been partially deaf as a baby and now you simply cannot hear the sounds of language correctly or your brain decodes them incorrectly?

Deafness is often not detected in babies and it is difficult to assess. But new parents should have their babies examined.

Talking to babies now makes a lot of sense, even when they can't understand a word you say, their brain is being programmed to decode the sounds of language. Make sure to talk to your baby, and make sure the baby can hear you.

With Permission:
Copyright 1999 New Scientist
ISSN 0262 4079. 24 July 1999 (P39 - 41)
Click here to see their website http://www.newscientist .com

Tongue tied

By the time you reach your teens you'll never learn to speak a new language like a native. Laura Spinney discovers why it pays to start young

FOR two weeks after her stroke, a 68-year-old patient, EM, was mute. Then she started to speak. On the face of it, she seemed to have made a complete recovery. But when her relations came to see her, they were puzzled because she answered them in Italian, her second language and one that she had rarely used. The language she had spoken every day of her life from infancy was the Veronese dialect of northeastern Italy, very different from standard Italian. While she could still understand her mother tongue, she was no longer able to utter a sentence in it. As far as her ability to speak the Veronese dialect was concerned, the stroke had neatly excised it.

EM is not the first patient to have an entire language or dialect wiped out after a stroke, and will certainly not be the last although it is far more common for the native tongue to be spared. But it is cases like hers that gave the first hints that non-native languages might be filed in separate areas of the brain from the mother tongue.

New research is now showing that where a language is represented in the brain depends on when—and, to some extent, where and how - it is learnt. True bilinguals who learn two languages together from birth show different patterns of organisation from those who learn a second language as a teenager or adult. And the foundations for that organisation may be laid down by our experiences very early in life - before we even learn to speak. By looking at what is happening in the brain at that time, researchers hope to explain why children are so much better at picking up languages than adults. And, perhaps, to offer us some tips as to how to compete with them.

A newborn baby is a bundle of potential as far as language is concerned. Infants can learn any language spoken to them and can distinguish between any sounds from any language. A six-month old Japanese baby can clearly hear the difference between the words "right" and "light", but when it comes to a Japanese tourist asking directions in New York or London, the potential for confusion is endless. The distinction between the "r" and "1" sounds is not made in Japanese, and by adulthood it appears to have been wiped from the Japanese brain. In fact, says Marie Cheour of the University of Helsinki's Cognitive Brain Research Unit, the distinction is erased before a child even learns to speak.

Last September, her group produced the first neurophysiological evidence that memory traces for sounds specific to certain languages, in this case Estonian and Finnish, develop before the age of one (Nature Neuroscience, vol 1, p 351, 1998). The Estonian and Finnish languages have very similar vowel structures, except that Estonian has one vowel, "o", that does not exist in Finnish. Its sound falls somewhere between "o" (which sounds like sierra vowel that is common to both languages—and "o" (which sounds like "or"). By monitoring the activity in the auditory cortex of six-month-old Finnish or Estonian babies, using a set of scalp electrodes, the researchers could see a clear signal (the "mismatch negativity" or MMN response) when an "o" or "o" was sounded as the odd-one-out in the middle [ of a string of other idenhcal vowels. This shows that the babies can easily distinguish the different vowel sounds. But by the age of one, the Finnish infants hardly noticed the odd "o", while the "o" still ; stood out. Their brains' capacity to hear the difference between "o" and other vowels had all but vanished.

'Memory traces for sounds specific to certain languages develop before we can even speak, by the age of one'

"When we learn a language we build permanent memory traces that represent our native language sounds to our brains," says Cheour. Without those memory traces, you cannot become a "native listener" of the language, and hence you are less likely to be able to speak it. As Cheour puts it, "If you don't hear the difference between two sounds, how can you say them correctly?"

Cheour's finding shows that there is a very early critical period in language acquisition, for establishing phonetic architecture—the first and crucial stage in learning a language. According to Patricia Kuhl of the University of Washington in Seattle, the hming of this critical period is dictated by our experience. She thinks that infants are born with certain innate boundaries for discriminating between speech sounds, and that these are either reinforced or pruned through experience. Sounds that are heard regularly in the native language are somehow captured as memory traces.

The memory traces for similar sounds that are considered by the brain to be examples of the same phoneme are all drawn together and treated as a single category, while the boundaries between different sound categories widen. In the Japanese case, "1" and "I" come together in a single cluster, but in the English language there will be a distinct boundary (see Diagram, p 40). Kuhl calls this the "perceptual magnet effect". Hearing the same sound over and over reinforces a particular representation. The critical period is defined by that reinforcement, ending when the connections can be reinforced no more. This collection of memor`,~ traces, which corresponds to all the sounds required by a particular language, can be thought of as a mental map, that allows us to process sounds in an ideal way for each language, says Kuhl.

When immersed in a foreign language, however, the map in your brain acts as a filter. Faced with a voluble New York cab driver, the non-English speaking Japanese tourist forces the speech through that filter. In the process, certain crucial distinctions are lost. Not only does the lapanese tourist not hear them, but when he or she responds in rudimentary English, his speech will also lack those distinctions. Hence it will sound heavily accented. But, says Kuhl, "in true bilinguals there are two distinct maps, one for each language".

Having two separate maps is important if two languages are to be spoken and understood well, but this doesn't mean that they have to be separated in space. In fact, the opposite may even be true. Although brain imaging hasn't yet allowed us to pick out the phonetic maps specifically, two years ago Joy Hirsch of the Memorial Sloan-Kettering Cancer Center in New York and her colleagues used functional magnetic resonance imaging (fMRI) to look at the speech region known as Broca's area. They showed that in bilingual people who learnt both languages early in life, the two are represented in overlapping regions of the left frontal lobe. "These data suggest that if multiple languages are acquired early in life, the brain treats them as if they were one language," says Hirsch.

Of course, it is possible that the two languages are separated on a finer scale that we can see using brain imaging methods. But the apparent overlap begs a question that often worries bilingual parents— whether they will muddle their child by speaking two languages together. If it's a case of two languages, one location, why don't the two don't get confused?

Arturo Hernandez of the University of California at Santa Barbara thinks he may have the answer. Two years ago, he used fMRI to eavesdrop on the brains of Spanish-English bilinguals as they named pictures first in one language, then in the other, or alternating the two. In the first two instances, their brains showed similar activation, but in the alternating task, the left prefrontal cortex seemed to be working overtime. Hernandez concluded that it was playing some role in reducing interference between the languages.

But it's only when two languages are learnt together early on that they seem to occupy overlapping areas. If a second language was acquired later, Hirsch found that two separate regions about 8 millimetres apart were activated within Broca's area (This Week, 12 July 1997, p 7). And this pattern isn't just seen in speech areas. The variability gets even greater if you take other areas that deal with semantics and syntax into account.

In 1997, a group led by Stanislas Dehaene of the CNRS, the French national research institute in Paris, asked late bilinguals—those who, like EM, acquired their second language after the age of seven— to listen to stories in one or other of their languages. This task required not only an analysis of the phonetic structure of the speech, but also an understanding of semantics, grammar, and so on. They used fMRI to show that the second language was associated with a variety of brain regions distributed across both hemispheres, and sometimes with the right hemisphere alone. Most children start speaking their first language at about the same age, explaining, perhaps, why the native language is normally associated with the same regions of the left hemisphere. But the second language may be acquired at any time, or even haphazardly over many years, which may explain the variability.

"The main message is that there are many critical periods," says Helen Neville of the University of Oregon in Eugene. The basic phoneme contrasts may have been carved out in the brain by the age of one—as Cheour's research demonstrates. And ideally, syntax and pronunciation should be in place by the age of seven— long before most English-speaking schoolchildren have even learnt to say "Bonjour". But word power is more malleable. You can go on building a vocabulary with ease well into adulthood.

The earlier you start to learn a foreign language, the better you will speak it. Nobody disputes that. But timing is not the only factor determining where a second language is represented in the brain. There are other influences, too. For one thing, it may depend on what the two languages are. "I think it is very likely that the first language learnt and its degree of similarity to a second language learnt strongly affects the organisation of the second language," says Neville. Spanish and Italian might be organised differently from, say, Spanish and German. And research presented to a meeting of the British Psychological Society in April suggests that where a second language is represented in the brain depends not only on when it was learnt, but where.

Sounds like: in the physical world (top), "ra" or "la" sounds are just collections of different frequencies. Different frequency components of the sound can be varied in equal steps, represented here by the array of points. But the brain doesn't hear them as equal steps. Instead the English-speaking brain separates the sounds Into two distinct groups, whereas the Japanese-speaking brain lumps the whole lot together

Judith Evans of the University of Glamorgan in Wales found that among teenagers who spoke both English and Welsh, the lateralisation of the second language, Welsh, depended on which part of Wales they came from. Among those who had grown up in the west of Wales, where both languages are spoken, Welsh was represented in the left hemisphere, regardless of when it was learnt. But in the Englishspeaking community of South Wales, the age when Welsh was learnt made a real difference: those who had learnt Welsh before the age of six showed a left hemisphere bias, while those who had acquired it later showed a bias to the right.

Just having a language wash over you in childhood, says Evans, ensures that the brain selects for it—or, to use Kuhl's terminology, creates a distinct phonetic map for it. You don't actually have to learn to speak it. As far as carving out the phonetic contrasts is concerned, listening is enough, although you still have to learn grammar and vocabulary. In fact, she adds, if you were to regularly play a foreign language radio station in the child's bedroom, it could have the effect of recreating that dual language environment. Your child wouldn't instantly start speaking the language, but if she learnt it later on she might pick it up more quickly and speak it with less of an accent.

'The best way to learn a language is to listen to the sounds in your cot, master the grammar by the time you can tie your shoelaces, then relax and learn the vocab at your leisure"

But while it's true that if you learn your second language after puberty, your chances of speaking it without an accent are reduced, it is not the case that linguistically, life ends at 13. Nobody ever said that adults couldn't learn a foreign language. If that were the case, Berlitz would be out of business, remarks Steven Pinker of MIT. "The difference," he says, "is that children don't need to be trained with artificial speech, don't need structured lessons and always succeed nonetheless."

But if we get the structure of the lessons right, there is still a surprising amount of give in the adultbrain, as a paper soon to be published in the journal Psychophysiology demonstrates. In collaboration with the Finnish group, Istvan Winkler of the Hungarian Academy of Sciences in Budapest found that a Finnish phoneme contrast that does not exist in the Hungarian language elicited almost no MMN in native Hungarians who knew no Finnish—as you might expect. But in Hungarians living in Finland who had learnt the language as adults, it elicited a large response, showing that the phonetic map can be taught some new tricks in adulthood. Which may mean that those memory traces are not as permanent as Cheour suggests.

Indeed, a group led by Jay McClelland of the Center for the Neural Basis of Cognition at the Carnegie Mellon University in Pittsburgh believe they have found a successful strategy for recreating some of the phonetic distinctions lost in the first year of life. At a meeting of the Society for Cognitive Neuroscience in Washington DC this April, McClelland described how in just three 20-minute sessions, 16 native Japanese speakers were trained to distinguish "road" from "load", and "rock" from "lock". They did this by using a computer to manipulate the first parts of the words to make the contrast between "r" and "1" as distinctive as possible, and the listeners tapped different computer keys according to which sound they thought they heard. The better they got, the less distinctive the sounds became, until eventually they were distinguishing sounds from the equivalent of slurred speech.

It's a promising finding, because it suggests that the phonetic maps, and hence the fate of our language skills, are not fixed in the sense that neurons are pruned and lost forever. Instead it looks as if connections can be regrown, and new language maps learnt, given the right learning methods. Most of the research suggests that the best way to learn a language is to listen to foreign sounds in your cot, to master the grammar by the time you can tie your shoelaces, and then to relax and learn the vocab at your leisure. But perhaps there is, after all, some kind of latent capacity to learn new languages, to which we have yet to find the key.

Laura Spinner is a freelance journalist

Further reading: The Neurolinguistics of Bilingualism: An Introduction, by Franco Fabbro, Psychology Press (1999)

"The development of speech and language" by P. K. Kuhl, in Mechanistic Relationships 8et~veen Development and Learning, edited by T. J. Carew and others, John Wiley and Sons, New York (1998)

"Neural organisation and plasticity of language" by H. J. Neville and D. Bavelier, Current Opinion in Neurobiology, vol 8, p 254 (1998)