Certain regions of the brains of autistic children develop much more slowly than in non-autistic brains, a new study reports.
As most of our brains mature throughout our adolescent years, our white matter – the tissue that connects separate brain regions and allows them to communicate with one another – undergoes vast amounts of growth, as areas like the parietal, temporal, and occipital lobes learn to work together more closely. In the brains of autistic adolescents, though, this white matter grows much more slowly.
Meanwhile, their gray matter – the tissue composed mostly of neurons’ cell bodies, where most intensive processing takes place – shows overgrowth in regions like the putamen and anterior cingulate cortex (ACC), which are heavily involved in social interaction. This study is one of the first to isolate such specific developmental differences in the brains of people with autism.
The term “autism” covers a wide spectrum of disorders, whose exact links and causes remain poorly understood – though people with autism tend to be united by certain symptoms, such as repetitive behaviors and difficulty developing social instincts. Autism disorders affect approximately one percent of the total U.S. population, and many researchers say that number is on the rise. Even so, scientists are only beginning to discover the neurological roots of many autism-related problems.
As the journal Human Brain Mapping reports, a team led by UCLA’s Jennifer Levitt set out to examine those roots by studying the brains of adolescent autistic boys under a T1-weighted MRI scan – a type of scan that yields especially clear images of white matter - and comparing those scans against equivalent ones of non-autistic boys’ brains.
Then, by re-scanning all those brains three weeks later, the researchers were able to track some intriguing changes, and discover some important developmental differences between autistic and non-autistic brains:
The typically developing boys demonstrated strong whole brain white matter growth during this period, but the autistic boys showed abnormally slowed white matter development, especially in the parietal, temporal, and occipital lobes. We also visualized abnormal overgrowth in autism in gray matter structures such as the putamen and anterior cingulate cortex.
In short, most lobes in the autistic boys’ brains showed abnormally low connectivity with other regions – while more primitive regions involved in reward, planning, empathy and emotion show abnormal overgrowth. These seem to be promising links between the neuroanatomy of autistic brains and some of the developmental hurdles faced by autistic children:
Our findings reveal aberrant growth rates in brain regions implicated in social impairment, communication deficits and repetitive behaviors in autism, suggesting that growth rate abnormalities persist into adolescence.
Still, it’s hard to say what exactly that overgrowth means. It’s possible that the putamen and ACC are more intra-connected than inter-connected in autistic brains, or it could be that their workloads are heavier for some reason – or it could be that they’re just developing differently in some way we don’t yet understand.
It also leaves another open question: what causes these developmental differences in the first place? Researchers have blamed everything from air pollution to white noise to genetics - but at this point, anyone who says they’re sure of a single cause is lying.
Though studies like this one may help teachers and parents tailor therapies to the autistic mind, we’ve still got a long way to go (or one hell of a major breakthrough) before we understand what exactly autism is – if it’s even one “thing” at all.
But I doubt that’ll prevent certain rude people from using self-diagnosed Asperger’s as an excuse.