Questions About Autism
- Published18 Feb 2016
- Reviewed18 Feb 2016
What’s different in the brains of people with autism?
When we study the brains of people with autism, we frequently find differences, but no one specific change. The irregularities we see are consistent with problems of brain development, and I think it’s fair to say that autism is a disorder of brain development.
One of the more interesting areas of research is exploring the number of connections, called synapses, between brain cells. Some evidence shows individuals with autism have too many synapses. During development, our brains make a profusion of synapses. As we grow, the weaker synapses are eliminated, and the strong ones are retained in a process called synaptic pruning. Autism could be related to problems with the pruning process. However, we can’t diagnose autism by looking at a brain and finding too many synapses. That’s in contrast to something like Parkinson’s disease, where the loss of dopamine-producing cells in a particular area of the brain really is the hallmark of the disorder.
At the same time, some research suggests individuals with autism have too few neurons in an area of the back of the brain called the cerebellum. While the cerebellum is involved in coordinating motor movement, we now know that it also communicates with networks involved in learning, memory, and language. People who have a cerebellar injury, either at birth or later, can have cognitive and social problems that have nothing to do with motor systems. There is also evidence that people with autism have less white matter, which are the physical connections between brain areas.
That’s not to say an individual with autism can’t have a perfectly normal looking brain from a structural point of view. Many cognitive tasks require communication between multiple parts of the brain. On average, individuals with autism have problems with this kind of communication between brain regions. As such, their brains likely function differently. Because of that they may not be able to do common tasks or they may do them more slowly or less efficiently.
Why does autism affect more boys than girls?
Autism is four to five times more common in boys than in girls. We don’t know why, but it is an area of active research. Male brains seem to be more vulnerable in general and are more likely than girls to develop neurological disorders. We don’t know why this is, but now geneticists are making some headway.
One idea is that girls may have some kind of protective factor, and girls would need a greater number of genetic insults in order to get a degree of autism equivalent to what you see in boys.
What are some of the current therapies for autism and what symptoms do they address?
Physicians use both behavioral and pharmacological (drug) therapies to treat autism. Only two drugs, risperidone and aripiprazole, are approved by the Food and Drug Administration to treat irritability in children with autism. These belong to a class of drugs called antipsychotics, and they are also used for schizophrenia and depression. Both of these drugs are good for treating psychotic behaviors including aggression and irritability. A lot of kids with autism also have anxiety so we prescribe the more typical antidepressants and anti-anxiety drugs as well.
However, none of these drugs treat the core symptoms of autism, which include problems with social interactions and restricted or repetitive behavior.
Behavioral interventions are probably more important and multiple research studies show they make a significant impact. The major intervention used is something called applied behavioral analysis or ABA. A psychologist will sit with a child with autism and identify their problems including skills that need to be developed and any unwanted behaviors. Then they develop a program to reward the positive behaviors and dissuade the negative behaviors by not providing a reward. ABA tries to teach new skills so the individual can build a repertoire of appropriate behaviors.
What therapies might be available in the future?
There have been very useful mice models of a lot of the genetic disorders associated with autism, including Fragile X syndrome and Rett syndrome. Using those models scientists have determined what makes the mice better, and this has led to the development of drugs that were then tested in children. One example is a class of drugs that dampen the effects of glutamate, the brain’s primary excitatory neurotransmitter. These kinds of drugs improved symptoms in a mouse model of Fragile X syndrome. In a clinical trial the drug didn’t succeed in curing enough of the kids, but it did help many of them. But autism may have many underlying mechanisms. If you’ve got between 500 and 1000 genes contributing to autism, you would never expect a single treatment to help everyone.
There’s also a fair amount of work going on now exploring the neurobiology of the brain’s social network. One of the most important peptides involved in social behavior in primates is oxytocin. It’s been found that oxytocin administration improves social interactions in all humans, and it seems to help in some people with autism. There have been a number of studies looking at oxytocin, and clinical trials are ongoing.
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