Gene links to memory, brain size found

An international effort to understand the genetic building blocks of the human brain and its functions found patterns of DNA that may be linked to memory and intelligence.

The research for the first time tracked genes that affect the size of infants’ heads, and the volume of the cranium and the hippocampus, a seahorse-shaped organ crucial for memory. More than 200 researchers at 100 medical centers worldwide were involved in creating a database of 21,151 people that helped lead to findings from a series of four studies.

The reports, published online by the journal Nature Genetics, featured two key results. In one, the scientists were able to link certain DNA to brain size. In another, they found a gene that may be tied to the rate at which the hippocampus shrinks as people get older. Paul Thompson, a researcher at the University of California, Los Angeles, said the findings wouldn’t have occurred without the collaboration.

“Our individual centers couldn’t review enough brain scans to obtain definitive results,” Thompson, a professor of psychiatry at the Semel Institute for Neuroscience and Human Behavior, said in a statement. By sharing data, “we created a sample large enough to reveal clear patterns in genetic variation, and show how these changes physically alter the brain.”

Traditionally, scientists have screened the genetic makeup of patients with specific disease seeking to uncover common mutations that may be linked.

In the most recent research, dubbed Project Enigma, scientists measured the size of the brain and its memory centers using thousands of MRIs, or Magnetic Resonance Imaging, scans from healthy people, while simultaneously screening their DNA.

“Earlier studies have uncovered risk genes for common diseases, yet it’s not always understood how these genes affect the brain,” Thompson said. Project Enigma “led our team to screen brain scans worldwide for genes that directly harm or protect the brain.”

Along with the findings on brain size, one of the teams studying the database found a weak association between certain DNA and intelligence quotient points. They reported that the gene seemed to raise IQ by 1.29 points. An average IQ, measured by a standardized test, is 100.

Because Alzheimer’s and other brain disorders disrupt circuitry in the brain, the newly established database will next be used to search for genes that influence how the organ is wired, he said. That search will use new technology, such as so- called diffusion imaging, which maps impulses that that occur in the living brain.

Thompson’s team worked with Nick Martin and Margaret Wright of the Queensland Institute of Medical Research in Australia, and molecular psychiatrist Barbara Franke at the Radboud University Nijmegen Medical Center in the Netherlands, according to the studies.

Funders for the research included the U.S. National Institutes of Health in Bethesda, Maryland, the Netherlands Organization for Scientific Research, the European Commission Framework Programme 6, and the National Institute on Aging, among others.