New Scientist: "Paediatricians routinely measure the circumference of children's heads during examinations. When the authors of the new study looked back at the medical records of 48 normal and autistic children aged two to five, they found that 60 per cent of the autistic children had head circumferences far above the norm when they were six to 14 months of age.
By contrast, only six per cent of the normal children had enlarged heads. The severity of the autistic children's symptoms was also correlated closely with the size of their heads during infancy.
During normal development, the brain grows slowly, and synapses, the connections among nerve cells, are retained or eliminated in response to sensory stimulation or motor activity.
Courchesne proposes that the unchecked brain growth seen in the study may undermine this synaptic strengthening and pruning process, leading to the social isolation characteristic of the disorder. 'They're developing synapses so rapidly that experience doesn't have a chance to determine which are maintained and which are eliminated,' he told New Scientist."