Researchers at the University of California, San Diego and the School of Medicine have found that the three-dimensional shape of the cerebral cortex – the wrinkled outer layer of the brain controlling many functions of thinking and sensation – strongly correlates with ancestral background. The study, published online July 9 in Current Biology, opens the door to more precise studies of brain anatomy going forward and could eventually lead to more personalized medicine approaches for diagnosing and treating brain diseases.
“If we can account for a large percentage of brain structure based on an individual’s genes, we’re in a better position to detect smaller variations in the brain that might be important in understanding disease or developmental issues,” said the study’s senior author Anders Dale, PhD, professor of radiology, neurosciences, psychiatry and cognitive science, and director of the Center for Translational Imaging and Precision Medicine at UC San Diego.
In their study, the researchers found they could predict with “a relatively high degree of accuracy an individual’s genetic ancestry based on the geometry of their cerebral cortex.”
They found no relationship between brain shape and functional or cognitive abilities, Dale said, but rather a trove of information about how minute differences in brain geometry could be correlated with genetic lineage.
“The geometry of the brain’s cortical surface contains rich information about ancestry,” said the study’s first author, Chun Chieh Fan, MD, a graduate student in cognitive science. “Even in the modern contemporary U.S. population, with its melting pot of different cultures, it was still possible to correlate brain cortex structure to ancestral background.”
Four continental populations were used as ancestral references: European, West African, East Asian and Native American. The metrics for summarising genetic ancestry in each ancestral component were standardised as proportions ranging from 0 to 100 percent.
“We looked to see how well we could predict how much genetic ancestry they had from Africa, Europe and so forth,” said study co-author Terry Jernigan, PhD, professor of cognitive science, psychiatry and radiology, adding that cortex differences between various lineages were focused in certain areas. “There were various systematic differences, particularly in the folding and gyrification patterns of the cortex,” said Jernigan, also director of the university’s Centre for Human Development. “Those patterns were quite strongly reflective of genetic ancestry.”
The researchers reported that the cortical patterns accounted for 47 to 66 percent of the variation among individuals in their genetic ancestry, depending on the ancestral lineage.
The researchers analysed data from the Paediatric Imaging, Neurocognition and Genetics study, a major data collection project funded by the National Institute on Drug Abuse and the National Institute of Child Health and Human Development in 2009. The project collected neuroimaging and genotyping data from more than 1,200 children and adolescents at 10 sites in the United States to create a data repository to advance research efforts worldwide. UC San Diego was the coordinating center for the PING study and Dale and Jernigan were its co-principal investigators.
Jernigan said the research team used a subset of PING data for the brain cortex study, analysing genetic and neuroimaging information from 562 children aged 12 years and older, a group chosen because the cortex surface changes little after age 12.