Five genetic variants that influence the size of structures within the human brain have been discovered by an international team that included a Georgia State University researcher.

In the study led by Drs. Sarah Medland, Margie Wright, Nick Martin and Paul Thompson of the QIMR Berghofer Medical Research Institute in Australia, nearly 300 researchers analyzed genetic data and magnetic resonance imaging (MRI) scans from 30,717 individuals from around the world. They evaluated genetic data from seven subcortical brain regions (nucleus accumbens, caudate, putamen, pallidum, amygdala, hippocampus and thalamus) and intracranial volume from MRI scans.

This is the largest analysis of brain structure and genetics ever done, said Dr. Jessica Turner, associate professor of psychology and neuroscience at Georgia State, who organized some of the teams collecting and evaluating data from participants with schizophrenia. The research consortium Enhancing Neuro Imaging Genetics through Meta-Analysis (ENIGMA) designed and implemented protocols for image analysis, quality assessment and genetic attribution to ensure data were consistent across the study.

The goal was to determine how common genetic variants affect the structure of these seven subcortical brain regions, which are associated with memory, movement, learning and motivation. Changes in these brain areas can lead to abnormal behavior and predisposition to disease.

Previous research has shown the brain's structure is strongly shaped by genetic influences. Identifying genetic variants could provide insight into the causes for variation in human brain development and help to determine how dysfunction in the brain occurs.

"The team looked at several million base pairs or locations on the human genome," Turner said. "Through a large-scale, international data sharing and data-analysis-sharing effort, we were able to actually successfully identify genetic effects on the hippocampus, putamen and other brain regions that no one had ever successfully identified genetics effects on before."

The researchers discovered five new genetic variants that influenced the volumes of the putamen and caudate nucleus. They also found stronger evidence for three locations in the genome that influence the size of the hippocampus and intracranial areas of the brain. The strongest genetic effects were observed for the putamen.

"Those are brain regions," Turner said, "that we know are involved in various psychiatric and neurodegenerative disorders. In trying to figure out the genetics that make them either larger or smaller, it could have great benefits for understanding mechanisms of these disorders."

Their findings were reported this week in the journal Nature.