If one were to summarize the state of brain research on autism in a sentence, it might be: “We have many findings, but little understanding.” Neuroimaging research on autism has been enormously productive in the past decades, including tens of thousands of results. But few of the studies have been replicated. We have therefore not been able to piece together a coherent picture of crucial brain features underlying autism.
One problem is heterogeneity: Children diagnosed with autism fulfill the behavioral criteria in the latest version of the “Diagnostic and Statistical Manual of Mental Disorders,” the DSM-5, but do not all have the same biological condition. ‘Autism’ probably includes many different neurobiological conditions that differ in their causes.
A foremost clinical goal in autism research is, therefore, not so much to find the cause and the treatment for the condition, but to find out whether there are biologically distinct types of autism, each potentially treatable in a different way. Consequently, we need to understand whether neuroscientific results tell us something important about ‘autisms’ and their differences — as opposed to findings that only reflect differences in the way we conduct our studies. Research on brain connectivity may serve as an example.
There is growing agreement that autism is not located in a specific part of the brain, but rather relates to the way different brain regions ‘talk’ to each other. A prominent technique in the study of brain-network communication is functional-connectivity magnetic resonance imaging (fcMRI), which tests whether activity changes are coordinated across different parts of the brain.
About 10 years ago, there appeared to be firm evidence that the brain in autism is underconnected — less coordinated than the neurotypical brain. But then, more and more published studies appeared to show the exact opposite.
As it turns out, different studies used slightly different methods
Read more here at Spectrum.