Family Brain Map: Up To 66% Of Grooves On The Outer Surface Of The Brain Correlate With Ancestry

outer surface of the brain
Ancestral background accounts for a large percentage of variation in the wrinkled outer-layer of the brain from one person to the next: study. Reuters

Eight cranial bones form the skull, scientists say, and variations in the shape of these bones relate to our ancestral background. A new study takes this past research one step further. A team from UC San Diego discovered the wrinkled outer layer of the brain may owe an equal amount to family inheritance.

Depending on personal lineage, cortical patterns resulting from genetic ancestry accounted for 47 to 66 percent of variation among people in the new study, the researchers say.

“Even in the modern contemporary United States’ population, with its melting pot of different cultures, it was still possible to correlate brain cortex structure to ancestral background,” Dr. Chun Chieh Fan, a graduate student in cognitive science, stated in a press release.

We know that our brains are malleable, so much so that our experiences and what we learn and even our most common daily thoughts influence the strength of its synaptic connections and the formation of networks. Our brains, it would seem, are sculpted as naturally as clay. Naturally, then, we would expect our family — and the many encounters and interactions such relationships entail — have an impact on our brains. However, does family influence go back even further, even deeper? Does genetic inheritance affect the outer layer of the brain?

To answer these questions, researchers led by Dr. Anders Dale, a professor of radiology, neurosciences, psychiatry, and cognitive science, dipped into data from the Pediatric Imaging, Neurocognition, and Genetics (PING) study. This 2009 project collected neuroimaging and genotyping data from more than 1,200 children and teens at 10 locations in the U.S. to create a research repository to be used by scientists around the world.

The surface of the brain changes very little after age 12, so the scientists of the current study analyzed genetic and neuroimaging information from a subset of PING participants: 562 children, all over the age of 12.

After examining each child’s genes to determine her or his lineage, the researchers next analyzed each child’s neuroimaging scans. The science team used a sophisticated software suite to map the cerebral cortex. After comparing the results to each child’s genetic data, the scientists next evaluated the overall data. What did they find?

Patterns Emerge

No relationship existed between brain shape and cognitive abilities. However, tiny differences in brain geometry uncovered by the software did correlate to genetics, specifically lineage.

Naturally, the genetics of all the children ran along a continuum, with each child representing, say, 40 percent of one lineage and 60 percent of another. Surprisingly, though, these percentages linked to “subtle, but systematic” differences, in Dale’s words, among cortex shapes. In particular, regional patterns of folding and gyrification — the convolutions which give the brain its wrinkled appearance — were the most informative features, the tell-tale signs of a child’s lineage.

Why is this important? One reason: an understanding of these differences will help scientists create appropriate standards of comparison when deciding what might be abnormal for a particular individual. Knowing which differences in brain topography are simply reflective of ancestry, a doctor would be able to focus instead on dissimilarities that might account for an illness or disease symptom.

Source: Fan CC, Bartxch H, Schork AJ, et al. Modeling the 3D Geometry of the Cortical Surface with Genetic Ancestry. Current Biology. 2015.

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