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Worldwide study unlocks the secrets of grey matter

A major international collaboration has produced the first genetic map of the cerebral cortex, identifying more than 300 genetic variants that influence the structure of the key brain region.

The cerebral cortex – often referred to as the ‘grey matter’ – plays a crucial role in thinking, information processing, memory and attention. It is the relatively thin, folded, outer layer of the brain. Its folds are a way of packing in more neurons, or brain cells.

The extent of the folds – which are measured by surface area – and the thickness of the cortex have previously been linked to cognitive abilities and various psychiatric traits, including schizophrenia, bipolar disorder, depression, attention deficit hyperactivity disorder (ADHD), and autism.

However, until now, not a lot was known about the genetic variants that influence the size of the surface area and thickness of the cortex.

More than 360 scientists from 184 different institutions contributed to the global effort, which has been published today in the prestigious journal Science.

The key analysis was conducted by Dr Katrina Grasby from the Psychiatric Genetics Research Group at QIMR Berghofer, as well as other researchers from the Institute, the University of Southern California and the University of North Carolina.

Dr Grasby said the researchers identified 306 genetic variants that influenced the structure of the cerebral cortex.

“We conducted this study to identify genetic variants that influence brain structure in order to shed light on how our genetics contribute to these differences among us,” Dr Grasby said.

“We found that the genetic variants that are linked to a smaller surface area of the cerebral cortex – or less folding – also contribute to a greater risk of ADHD, depression and insomnia.

“This gives us a starting point to further explore this genetic link between the structure of the brain and ADHD.

“Our findings are now a resource that can be used by other scientists to help answer more questions about the genetic influences on the brain and how they relate to numerous behavioural or disease outcomes.”

QIMR Berghofer’s Associate Professor Lucía Colodro-Conde, who was also a co-author, said the researchers studied MRI scans and DNA from more than 50,000 people.

“By analysing brain images and genetic information from such a large group of people, we were able to predict one third of the differences in cortex structure between individuals with genetic variants,” Associate Professor Colodro-Conde said.

“It is only by bringing together data through these major, international collaborations that we can continue to unpick the highly complex relationship between our genes, brain structure and various disorders.”

The study was conducted within the ENIGMA consortium – a collaboration of more than 900 scientists from 45 countries investigating the genetic influences on the brain and the role of brain structure and function in disease.