Researchers probe source of language impairment in autism
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Compound noun: Hearing a made-up word like ‘donkey kicker,’ children with specific language impairment and children with autism and language problems both choose the picture of a donkey kicking a man rather than the one of a man kicking a donkey.
When toddlers fall behind in developing language skills, it is sometimes a warning sign of autism. But in other cases, the children are diagnosed with specific language impairment (SLI), a condition characterized by speech difficulties that can’t be explained by other physical or cognitive problems.
SLI is one of the most common learning disabilities, affecting perhaps seven percent of children. Some genes linked to SLI, including CNTNAP2 and CMIP, may also play a role in autism.
About half of all children with autism have some degree of language impairment, and for nearly two decades, scientists have debated the relationship between autism and SLI. Some have argued that language impairment in children with autism is the same as SLI, and that those children have a ‘double hit’ of disorders1.
“Comorbidity is the rule, not the exception, in developmental disorders, so I’m not sure why comorbidity with SLI has become such a controversial idea,” says Courtenay Norbury, reader in developmental neuropsychology at Royal Holloway, University of London.
Others maintain that language impairment in autism is distinct from SLI, with a different underlying cause2.
For example, although the two disorders look similar in toddlers, they tend to diverge once the children reach school age, notes David Williams, lecturer in psychology at Durham University in the U.K. “For one reason or another, the type of language problems that you see in autism change, whereas they don’t in SLI,” he says.
What is clear is that both autism and SLI are complex, heterogeneous disorders without clearly defined causes — and perhaps as a result, the relationship between them has proved particularly difficult to untangle.
Three papers published in the past several months engage the debate about the relationship between the disorders, but their findings suggest that it is far from settled.
“You really have to do a very stepwise, detailed, incremental study of all of language, especially with a focus on cognitive and neurobiological components of it,” says Timothy Roberts, vice chair of research in radiology of the Children's Hospital of Philadelphia. “Only then can you make a generalizable statement.”
Repetition rates:
In one of the new studies, published in June in the Journal of Autism and Developmental Disorders, researchers asked 15 children with SLI and 17 with autism and language impairment to repeat made-up words such as ‘flebitorgist’3. They found that the children in these two groups don’t make the same type of errors in repeating these ‘non-words.’
“If language impairment in autism simply is SLI, then to my way of thinking you should show the same problems with non-word repetition,” says Williams, a member of the study team.
People with SLI tend to make specific types of errors in doing this task. For example, they have more difficulty repeating consonant clusters in the middle of a made-up word than at the beginning. Errors on the task persist even if an individual’s language improves as a result of therapy, and are considered biomarkers for SLI. “Research on non-word repetition has been central to our understanding of SLI,” says Williams.
Some earlier studies have found that children who have both autism and language impairment also struggle with non-word repetition4, but they did not work out the details.
In the new study, Williams and his colleagues found that children with autism and language impairment perform similarly to language-matched controls — children developing typically who are a few years younger — and not to those with SLI.
“We should start trying to think about what causes language impairment in autism uniquely,” Williams says. “Even if there is some overlap with SLI, I think it’s very difficult to say it’s just SLI.”
Others see the results as less definitive, however.
“I don’t think that’s such a compelling argument, because the kids who have autism and language impairment also have autism,” says Norbury, who was not involved in any of the three new studies. “Kids with autism have other difficulties that are going to color their performance on these tasks.”
For example, non-word repetition might be linked to the repetitive behaviors that are characteristic of autism, adds Roberts, who was not involved in the work. Still, he praises the team’s fine-grained approach. “They’ve made an attempt to go after the cognitive underpinnings [of this task],” he says. “I think that’s exactly right.”
Nonsensical nouns:
A second study, yielding evidence in the opposite direction, compared the ability of 14 adolescents with SLI and 16 with autism and language impairment to interpret made-up compound nouns5. The participants listened to a taped voice reading simple sentences featuring the nouns, and had to choose which of a pair of pictures best illustrates each one.
One part of the study focused on synthetic compound nouns, which consist of a noun paired with a second, verb-derived noun, such as ‘donkey kicker.’
“We found similar performance in the children with SLI and in children [who have] autism with language impairment,” says Nick Riches, lecturer in speech and language pathology at Newcastle University in the U.K.
The two groups of participants frequently reverse the meaning of these compounds, choosing the picture of a donkey kicking a man rather than one of a man kicking a donkey, for example. In contrast, participants with autism who have normal language skills do as well on this task as healthy controls do.
The results “contribute to this hypothesis that there is an overlap in these two disorders,” Riches says.
According to Norbury, one strength of this study is that the researchers recruited participants through a population-based survey. “Sometimes when you’re picking kids up from clinics or special schools, they might have more comorbidity or more difficulty anyway, so you kind of get a selection bias,” she says. “But the fact that they for the most part are looking at a population sample there makes it reasonably strong evidence that this is a real thing.”
However, Williams says the analysis is too superficial to draw any firm conclusions.
“The test performance itself is merely an example of behavior,” he says, and it doesn’t necessarily reflect the same mechanism at play in both autism and SLI.
The third study, published in May in Neuroreport, attempts to parse the similarities and differences between autism and SLI6.
Roberts and his colleagues used magnetoencephalography to record the brain’s response to sound in children with SLI. They found that one measure, called the mismatch field, is delayed in children with SLI, as it is in children with autism7.
However, they found that the M100, another measure of the brain’s response to sound, is delayed in children with autism8 but not in those with SLI.
Taken together, the results suggest that it is possible to identify distinct signatures — and underlying mechanisms — for the two disorders.
Norbury says this type of research is promising. “What it helps you do is see what is specific to autism,” she says, “and what might be more aligned with the language impairment component.”
References:
1: Tager-Flusberg H. and R.M. Joseph Philos. Trans. R. Soc. Lond. B Biol. Sci. 358, 303-314 (2003) PubMed
2: Williams D. et al. Psychol. Bull. 134, 944-963 (2008) PubMed
3: Williams D. et al. J. Autism Dev. Disord. Epub ahead of print (2012) PubMed
4: Whitehouse A.J. et al. J. Commun. Disord. 41, 319-336 (2008) PubMed
5: Riches N.G. et al. Int. J. Speech Lang. Pathol. 14, 307-317 (2012) PubMed
6: Roberts T.P. et al. Neuroreport 23, 463-468 (2012) PubMed
7: Roberts T.P. et al. Biol. Psychiatry 70, 263-269 (2011) PubMed
8: Roberts T.P. et al. Autism Res. 3, 8-18 (2010) PubMed
Comments
http://deevybee.blogspot.com/2010/12/whats-in-name.html Please read Dr. Bishops post, which is very much related to this. We all live on the human spectrum.
I think one of the problems the autistic have with speech is down to the OCD side of their personality, which shows up in perfectionism (doubt / lack of confidence) in the higher functioning. With names your mind goes ‘Is that the same sound, despite the difference in spelling or is it a different pronunciation?’ With just words, your mind is thrown by syllables in the same way, mostly because of all the variations in vowels / vowel combinations but also because of double letters, silent letters, archaic and foreign variations. To me it is no wonder we don’t speak until three or four, under these circumstances. On top of this as Dr Cheri Florance points out in ‘Maverick Minds,’ we abandon speech for vision. This further confuses things because we take photographs of reality, not film it as a sequence of images. Like a roulette wheel, we see words click slowly round to form a sentence, whereas ordinary people don’t slow down this process and rush through, making mistakes just in order to say something and communicate to others.
Perhaps learning to sing would help close these gaps and make learning easier as has been found with other processing problems - stuttering, Alzheimers and Tourettes for instance have all found this beneficial.
Of course another thing is that the meaning of words varies too, whether through words with multiple definitions or through combination with other words as in phrases and idiomatic English.
The way I view verbal communication is as dispersed (released / relaxed) attention, whereas vision is concentrated attention (fixed viewpoint). When we talk, we do not see. Likewise subjective rambling by the mind, internally, equally means we are blind to physical (external / objective) reality. To use an analogy, it is like a toad swallowing and its eyes popping into its head, to assist the process - vision and verbalisation are mutually exclusive I would say from my observations.