Diffusional kurtosis imaging of the corpus callosum in autism.
Yu Veronica Sui, Jeffrey Donaldson, Laura Miles and 3 others
PMID 30559954WHAT IT FOUND
Young adults with autism had lower measures of axon packing and water movement inside axons in the corpus callosum, mainly mid and posterior regions.
Processing speed was lower, but these callosal measures did not predict processing speed in autism.
Key findings
01The autism group had lower processing speed index scores and lower scores on both processing speed subtests than controls.
02Axonal water fraction was lower in the autism group than controls, with corrected differences in callosal segments 3 to 5, and intra-axonal diffusivity was also lower.
03Callosal diffusion metrics predicted processing speed scores in controls but not in the autism group.
STILL TO COME
How it was doneWhat they found
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What it does not show
The sample was small: 17 controls and 16 adults with autism. Only young adult males with autism and no intellectual disability were included, so it does not speak to females, children, or people with intellectual disability. The study did not follow participants over time, so it cannot show that callosal differences caused processing speed differences. The imaging model assumes idealized axon organization. No differences were found in extra-axonal or traditional diffusion measures. One missing processing speed subtest score was imputed from another subtest score.
Declared interests
Funders named were the National Institute of Mental Health and the National Alliance for Research on Schizophrenia and Depression.
The easy way to misread this
Do not conclude that these callosal imaging differences explain why a patient with autism has slower processing speed. The study did not follow participants over time, and callosal measures did not predict processing speed in the autism group.