Written by Mark Krongold:
Over the past thirty or so years a large number of studies have been done in an attempt to describe the relationship between the structure of the brain and autism. For example, researchers found that the rate of brain growth is faster during the first few years of life in children with autism compared to typically developing children (Lainhart et al. 1997). However by mid childhood the average brain of an autistic child is no longer larger (Herbert et al. 2003). Importantly it is largely during this period of middle childhood when cognitive and behavioural functions begin to deteriorate in children with autism. This has led researchers to believe that whatever changes occur in the brain that bring the “autistic brain” back to normal size are likely some sort of compensatory mechanism.
A research group out of the University of Utah has looked into studying the brain growth trends of children with autism with the ultimate goal to eventually be able to detect early on which children will grow up to have autism.
The researchers studied both autistic and typical children and adults between the ages of 3 and 39 using MR images of their brains. A number of participants were scanned multiple times at different ages allowing the researchers to look at longitudinal trends of brain development. Using advanced analysis techniques the researchers were able to look at the thickness of the cortical sheet in a number of different regions across the brain.
There were three interesting findings from this study. Firstly, the researchers determined that there is no difference in the thickness of the brain in very young children. However by the age of three children with autism had an abnormally large brain thickness. Second, during the middle of adolescence the brain of autistic children goes through a phase of fast thinning. This explains why there are no large size abnormalities in the autistic brain during childhood and the teenage years. Interestingly this thinning seems to occur earlier in the frontal regions of the brain (regions that are associated with advanced executive mental processing). Third, there is a gradual decrease in the thinning of the autism brain during early adulthood. This however does not appear to happen in every region of the brain.
Unfortunately, at this point the researchers were not able to find specific growth trends that would allow one to predict which children will eventually be diagnosed with autism. The trends that these researchers discovered are so far not specific enough.
This study was a good step towards determining differences in the brain between children with autism and typically developing children. There are, however, a number of ways in which this study could be taken. More data is always welcome and a more complete longitudinal data set with more time points would help researchers better determine trends in brain growth. Finally, since autism is a spectrum disorder with a huge number of different ways in which symptoms present, research looking into how to distinguish between subtypes of the disease is also needed.
Lainhart JE, Piven J, Wzorek M, Landa R, Santangelo SL, Coon H, et al.Macrocephaly in children and adults with autism. J Am Acad Child Adolesc Psychiatry1997;36:282-90.
Herbert MR, Ziegler DA, Deutsch CK, O'Brien LM, Lange N, Bakardjiev A, et al.Dissociations of cerebral cortex, subcortical and cerebral white matter volumes in autistic boys. Brain 2003;126(Pt 5):1182-92.