Even when researchers do think they’ve found a match between an autistic person’s behavior and an anomaly in the brain, they can’t be sure that someone else manifesting the same behavior would have the same anomaly. Part of the title of a 2009 autism study in the Journal of Neurodevelopmental Disorders captured the situation succinctly: “Same Behavior, Different Brains.” In other words, just because you’re prone to extreme anxiety doesn’t mean your autistic brain has an enlarged amygdale…. Conversely, when researchers find an anomaly in the brain, they can’t be sure that that anomaly will have the same behavioral effect in a different brain. Or any effect, for that matter.Neurologists have a habit of scanning the brains of someone with neurological symptoms, finding a lesion,and assuming that the lesion is causing the symptoms. But since scans of perfectly healthy people also show lesions, there is no real reason to think this is true.
I particularly appreciated this take down of fMRI imaging, which I think tells us very little about what is going on in our brains:
Neuroimaging also requires subjects to keep their heads still. In recent years, several studies reported that short-range connections in the brain weaken as children grow older, while long-range connections strengthen. Neuroscientists considered this news to be quite a significant advance in understanding of the brain’s maturation process. Unfortunately, a follow-up study by the authors of the original studies showed that the supposed changes in the brain’s development disappeared once they took head movement into account. “It really, really, really sucks,” the lead investigator said. “My favorite result of the last five years is an artifact.”At least he admitted it.
Grandin does the same thing with hype about "autism genes." Early studies found genetic abnormalities in autistic patients, and this led to a lot of excitement about a genetic cause. But the more studies people do, the more different abnormalities they find, and most of the abnormalities are unique.
"We really don't know" is a frustrating thing to hear over and over again, but much of the time it is all that truthfully can be said.