Spectrum: Autism Research News
The signature is there but may be hard to see
There must be brain differences in autism, because the brain underlies all cognition and behavior — and the cognitive-behavioral differences that characterize autism can be so evident. The brain differences might be subtle or hard to find, as with cognitive and behavioral features. They might change over the lifespan or overlap with other conditions. But they are there.
Autism encompasses a wide spectrum of behaviors and severities, and probably multiple subtypes derived from different biological causes. This helps explain the difficulty of replicating brain-imaging findings. Every study involves its own mix of people with autism and different proportions of different subtypes.
At the same time, conditions of brain development show overlap — in both behavior and brain structure. You can think of a gigantic Venn diagram with autism, obsessive-compulsive disorder, ADHD and all sorts of other conditions showing some common traits but many unique ones. This complexity poses a challenge for research and for treatment, but it’s not true that there are no differences between the conditions. It’s just difficult to find them, and they’re not always black and white.
Some important questions are: Do we have the technology to look at something really subtle yet, and do we account for individual variability and potential subtypes?
In my lab, we are using advanced anatomical and diffusion MRI to look closely at the microstructure of the cerebral cortex and using analytic and statistical approaches that account for individual variability. By combining multiple MRI approaches, we are able to look at brain structure in more detail and with greater precision than with traditional MRI alone.
We hope to use this approach to spot small areas of blurring at the boundary between gray matter (neuronal cell bodies) and white matter (neuronal fibers), for example. These patches would indicate areas of disorganization in the cerebral cortex, and their location may vary from one individual to the next.
That kind of variation would be missed in traditional group comparisons but would help explain some of the variation in past studies’ findings. For example, individuals with patches in the social cortex may have more severe social issues, whereas those with patches in prefrontal areas may have more trouble with attention or self-regulation. We don’t expect to see these anomalies in more than a fraction of people with autism, but spotting them could help with identifying subtypes of the condition.