Neurological studies have shown some key elements in the early development of autism.

Cognitive neuroscientists at San Diego State University have found that in children and adolescents with autism spectrum disorder, more basic parts of the brain become very well connected, at the expense of later-developing higher-order functions.

Specifically, the connections between the cerebral cortex and the cerebellum appear to be overdeveloped in sensorimotor regions of the brain, which means there is less “real estate” in the brain for connections that serve higher cognitive functioning.

The findings provide another piece in the puzzle that could one day lead researchers to develop a reliable brain-based test for identifying autism.

“By the time the higher cognitive functions begin to come online, many of the connections are already specialised,” research psychologist Ralph-Axel Müller.

“If a particular part of the brain is already functionally active in one domain, there may be no reason for the brain to switch it over to another domain later in life.”

Returning to the real estate metaphor, it is as if the available land is scooped up by sensorimotor connections before the higher-order cognitive function connections have a chance to put together a deposit and move into the neighbourhood.

The findings could help scientists and clinicians better understand exactly how abnormalities during brain development lead to various types of autism spectrum disorder.

Müller hopes his work will not only contribute to a brain-based diagnosis of autism, but also be a step towards identifying its various subtypes and underlying genetic factors.

“We still don't understand what in the brain makes a kid autistic,” he said.

“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.”