For ten years Jo Eddings felt that she had been banging her head against a brick wall. “I can’t describe my frustration. I felt so helpless,” she says. “What I wanted was help with my very bright daughter who had a problem with language.” She was slow to learn to talk and at 9 her reading and writing were still poor.

“We took her to psychologists and all sorts of experts, but for years nobody seemed to be able to give us a proper diagnosis or know what to do.” But that changed this month when she heard a radio programme about an exhibition called Genes Talking at the Institute of Contemporary Arts (ICA) in London. It was about a research project to discover a gene linked with a condition known as specific language impairment (SLI). “As soon as I heard it I knew that this was what I’d been looking for,” she says. “I wasn’t alone, I wasn’t mad; there was someone who understood my daughter.”

SLI covers a range of speech and grammar problems suffered by children, the most familiar of which is dyslexia. About 8 per cent of children are recognised as dyslexic. But a similar number may be suffering from other forms of SLI and are not recognised.

The condition is the failure of different parts of the brain to process speech and language; and different failures manifest themselves in different ways (see box). And while dyslexia is now catered for, children with other SLIs are often written off as disruptive or not very bright.

The scientist involved in the ICA project was Professor Heather van der Lely, the director of the Centre for Developmental Language Disorders and Cognitive Neuroscience at University College London, and a leading expert on SLI. “If we can find a genetic link, it will provide the kind of hard evidence that this is a genuine problem, which is needed if we are to get funding bodies to take it seriously,” she says.

But distressing as SLI is for the families involved, it is also a boon to researchers such as Van der Lely who are trying to understand how it is that the brain pulls off the remarkable feat of learning a language at all. Think of it: you are a baby who’s just arrived in the world; you are surrounded by large beings who direct streams of noise at you and to one another; and somehow, miraculously, your brain is not only able to split those streams into discrete bits but also to work out, quite unconsciously, the complex rules for putting them together again and to construct your own speech stream. And let’s not even think about how the brain manages the business of attaching meaning to sounds.

Van der Lely and her team are edging closer to understanding some of the brain mechanisms involved, thanks to a remarkable device that looks like a hairnet studded with 128 ultra-sensitive electrodes. It’s placed over the head of children as young as a few months old as “they are easy to distract”, says Elena Kushnerenko. This friendly Russian post-doctoral scientist is becoming expert at slipping it on in a single move. “But some of the older ones seem to enjoy trying to take it off.”

The electrodes record the tiny electrical currents given off by active groups of neurons in the brain. “It allows us to track the pattern of neurons firing all over the scalp in real time when you hear a sound or word in a sentence,” says van der Lely. “The brain’s response to language is incredibly fast.” When you hear a single word, the neurons start responding within about 100th of a second, which means that the more conventional brain scanners are no good for this work. They can record only what is going on every three to four seconds.

So how does the high-speed hairnet help researchers to get a better understanding of SLI? Take the case of “Peter”, who had a language problem that seems odd at first sight but is common in these children. He finds it hard saying or understanding sentences that contain pronouns.

If you say to him “The farmer went to market with his son”, he knows what you’re talking about. But say “The farmer went to market with his son but then left him behind and came back by himself” and he’s stumped. That’s because the part of his brain that deals with word order in a sentence — syntax — can’t handle anything that doesn’t follow the most basic arrangement of subject, verb, object. Pronouns are too much of a stretch.

“Pronouns are hard because it’s often not obvious from the word order in a sentence what they refer to,” says Van der Lely. “Difficulty with questions is also a sign of a syntactic SLI.”

With a child like Peter, the hairnet allows van der Lely and her team to monitor the ultra-rapid changes in brain-wave activity as each of the different brain processes — syntactic and others (see box) — swing into action to decode a sentence. She has found, and this is the clincher, that groups of normal children produce different neuron-firing patterns when listening to sentences to those of SLI children. “This shows that they are not stupid but that their brains handle language in a different way and the reason is almost certainly genetic,” she says.

Children with SLI often come out with nonsense sentences such as: “Who did Joe see someone.” Now, if you play sentences like this to normal children who are wearing the hairnet, a pattern of brainwave activity will appear that’s known as a “rule violation response”, the neural equivalent of: what? One of van der Lely’s projects is to test whether this “violation” response shows up when SLI children hear nonsense sentences. She doesn ’t think it will. “Even if they spot that something’s wrong,” she says, “the pattern of responding may still be different.”

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