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Scientists used a type of magnetic resonance imaging (MRI), known as diffusion weighted imaging, to measure the brain connectivity in 260 infants at the ages of 6 and 12 months, who had either high or low risks of autism . The lengths and strengths of the connections between brain regions was used to estimate the network efficiency, a measure of how well each region is connected to other regions. A previous study with 24-month-old children found that network efficiency in autistic children was lower in regions of the brain involved in language and other behaviours related to autism. The goal of this new study was to establish how early these abnormalities occur. Lead author John Lewis, a researcher at the Montreal Neurological Institute and Hospital of McGill University and the Ludmer Centre for Bioinformatics and Mental Health, found network inefficiencies had already been established in six-month-old infants who went on to be diagnosed with autism. Inefficiencies in the six-mon...

"Aberrant synapse formation is important in the pathogenesis of schizophrenia and autism," says Osaka University Professor Toshihide Yamashita, one of the authors of the study. "Microglia contribute to the structure and function of synapse connectivities." Microglia are the only cells in the brain that express the receptor CX3CR1. Mutations in this receptor are known to affect synapse connectivity and cause abnormal social behavior in mice. They have also been associated with neuroinflammatory diseases such as multiple sclerosis, but no study has shown a role in neurodevelopment disorders. Working with this hypothesis, the researchers conducted a statistical analysis of the CX3CR1 gene in over 7000 schizophrenia and autism patients and healthy subjects, finding one mutant candidate, a single amino acid switch from alanine to threonine, as a candidate marker for prediction. "Rare variants alter gene function but occur at low frequency in a population. Th...