​In early childhood, the neurons inside a child's developing brain forms connections between various regions in the brain.​

Cognitive neuroscientists at San Diego State University found that in children and adolescents with autism spectrum disorder however, connections between the cerebral cortex and cerebellum appear to be overdeveloped in the sensorimotor regions of the brain. This overdevelopment appears to muscle out other connections serving higher cognitive functions.

SDSU psychologist Ralph-Axel Müller—working with Amanda Khan, a former master's student at SDSU and now a doctoral candidate at Suffolk University in Boston—used fMRI brain imaging technology to home in on neuronal patterns in 56 children and adolescents, half with autism and half without the disorder.

The imaging results revealed the participants with autism had far stronger neuronal connectivity between sensorimotor regions of the cerebellum and cerebral cortex than their non-autistic counterparts. But the autistic kids and teens also tended to have less connectivity between regions involved in functions such as decision-making, attention, and language.

The study represents the first-ever systematic look at connections between the entire cerebral cortex and the cerebellum using fMRI brain imaging. Its findings could one day help researchers to develop a reliable brain-based test for identifying autism.

"We still don't understand what in the brain makes a kid autistic," Dr. Müller says. "You can't look at a scan and say, 'There it is.' We're doing the groundwork of finding brain variables that might be biomarkers for autism and its subtypes."