Among the 15 nerve-fiber tracts in the brain that linked various regions together, 12 showed aberrant growth patterns in the 6-month old babies who developed ASDs compared with those who didn’t. This suggests, says Dawson, that “there is a more global change in development of these tracts implicated in autism, and that functional connectivity, or the establishment of neural networks is clearly implicated in these findings.”
That means that whatever biological processes are driving autism, they aren’t limited to one region of the brain. And that makes sense, since the disorder’s hallmark behavioral symptoms involve language and social interactions, which require exquisite coordination of several different brain areas.
Dawson and her colleagues stress, however, that their results do not necessarily suggest that the explosion of white matter at 6 months and its subsequent drop-off cause the abnormal development that leads to autism. For now, it’s just an intriguing potential marker for the disorder, one that may help doctors identify infants at highest risk of developing autism early on. Because the study involved only children with a family history of ASD, the next step will be to compare these infants with those whose families are not affected. (There is evidence that even unaffected siblings of autistic children have similar brain changes to those of their autistic brothers and sisters, and may even exhibit subtle symptoms of the disorder.)