Autistic Spectrum Disorders

Over the last few months I have reported on a number of advances in our understanding of autism, and I was pleased to see that Time magazine has autism as this week’s cover story.The writers at Time are really to be congratulated on having put together a first rate set of articles.

Although we often use the term autism as shorthand, we prefer to use the term Autistic Spectrum Disorders (ASD), as autism is not one illness, but rather represents many illnesses with many distinct causes. The illness can range from profound disability to mild forms that may even be advantageous. One of the mild forms that has attracted a great deal of interest on recent years is Asperger’s syndrome, in which people may be highly intelligent, but are typically clumsy and have poor social awareness. There has been speculation that a number of highly successful scientists, writers and innovators may have the disorder.

One of the great puzzles of these illnesses is that they appear to be becoming more common. Even when you take into account changing diagnostic criteria and a greater awareness of the illnesses, they genuinely seem to be becoming more common. It is not surprising that a whole long list of culprits has been examined, from vaccinations to radiation and food additives. But so far no credible cause for the increase has been identified.

Last December I wrote an item about mirror neurons in the prefrontal cortex and their relevance to ASD. This research was part of a large series of brain studies being conducted around the world. For many years we thought that the key regions of the brain involved in autism were in the cerebellum, a “second brain,” that lies at the back and underneath the cerebral hemispheres. This structure is involved in coordinating movement, in language, emotional processing and some social functions. But now it is becoming clear that many regions of the brain are affected. Investigators from London have just published a study indicating that some of the difficulties in relating to others that are experienced by people with ASD may be due to poor communication between brain regions. People were asked to look at pictures of faces or houses, while their brains were scanned. In healthy volunteers, paying attention to pictures of faces caused a significant increase in brain activity. However, in the people with ASD, paying attention to faces made no impact at all on the brain, explaining their lack of interest in faces. It seems that the areas of the brain concerned with decoding faces are not well connected to those parts of the brain that control attention.

Just last week, investigators from University of Texas Southwestern Medical Center in Dallas, and St. Jude Children’s Research Hospital in Memphis, published a study concerning a gene named Pten. This gene has already been linked to some rare gene disorders, and is involved in controlling the numbers and size of neurons. In mice that did not have a normally functioning gene, parts of the cerebral cortex and hippocampus did not develop normally, and the mice showed some odd deficits in their social functioning: The genetically altered mice were socially less skilled, being rather incurious about new animals coming into the cage. They also showed the same level of interest in an empty cage and in one containing another mouse, something very similar to the behavior of some children with ASD. The genetically altered mice were also less likely to build nests or look after their young. But they were more sensitive to stressful stimuli, such as loud noises or being picked up. Again, these are common features in children with ASD. The brains of the mice were also larger than those of their littermates, which is again something that has been picked up in many brain imaging studies in children with ASD. I have warned many times about trying to extrapolate from animal studies to human: Social abnormalities in a mouse may be caused by entirely different factors from human social abnormalities. But this new finding is another brick in the wall.

Professor Simon Baron-Cohen from the University of Cambridge has proposed that a central cognitive problem is ASD a result of developing extreme male tendencies to analyze and systematize rather than to empathize. His group has also just published data in the Archives of Disease of Childhood, indicating that highly analytical couples, may be more likely to produce children with ASD.

One of the things that often worries me is that desperate parents have sometimes been persuaded to try treatments that may actually do harm. Not so much from the therapy being toxic, but rather because the child may then not get the treatment that he or she needs. ASD is a prime example of a group of conditions that do best with an integrated approach: physical care, nutrition, cognitive, psychological and social skills work. And it is essential to ensure that other family members also receive help and support.

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