DNA plays far greater role in intelligence, UCLA study shows.

Scientists take pictures of math ability in brains
SCIENCE: DNA plays far greater role in intelligence, UCLA study shows.
City News Service
Updated: 03/22/2009 09:20:55 PM PDT


Click photo to enlarge«12»UCLA researchers have used a new type of brain scanner to find the inherited physical characteristics - the very hard-wiring of the brain - that determine a person's degree of intelligence.
And for those who have always suspected that the ability to handle math is a matter of how a person's brain is wired, the new University of California, Los Angeles, study confirms that folk theory. The section of brain used for mathematical computations may be 85 percent reliant on hereditary for the amount of a certain material that facilitates thinking, UCLA scientists said this week.

Neurologists for the first time have been able to look at chemicals that wrap around the brain's axons, which are the wiring that sends signals through the brain. The faster the signaling, the faster the brain processes information, UCLA researchers said.

And since the integrity of the brain's wiring is influenced by genes, the DNA we inherit plays a far greater role in intelligence than previously thought, said UCLA neurology professor Paul Thompson. Genes determine how much insulation, in the form of myelin, is wrapped around brain axons allowing for fast signaling bursts in our brain, and therefore, greater intelligence.

The thicker the myelin, the faster the nerve impulses, and the greater degree of intelligence, Thompson said.

Various parts of the brain are responsible for different thought processes and those areas have differing amounts of the myelin that is regulated by heredity, the researchers found. The amount of myelin in the section of the brain used heavily for mathematical calculations, for example, indicates that mathematical ability may be 85 percent hereditary.
The brain lobes that handle vision may be 76 percent reliant on genetic factors, and the lobe that handles planning, inhibition and self-control may be 65 percent reliant on genetic influence.

Capability for learning and memory was calculated at only 45 percent on genetic factors.

The UCLA neurologist believes identifying the genes that promote high-integrity myelin is critical to forestalling brain diseases like multiple sclerosis and autism, which have been linked to the breakdown of myelin.

"The whole point of this research is to give us insight into brain diseases," Thompson said. Thompson and his colleagues scanned the brains of 23 sets of twins and 23 sets of fraternal twins because identical twins share the same genes while fraternal twins share about half.

Researchers were able to compare each group to show that myelin integrity was determined genetically in many parts of the brain that are key for intelligence. These include the parietal lobes, which are responsible for spatial reasoning, visual processing and logic, and the corpus callosum, which pulls together information for both sides of the brain.

During research, they used a high-angular resolution diffusion imaging scanner that examines the brain at a much high resolution that a standard MRI. While an MRI shows the volume of different tissues in the brain by measuring the amount of water present, HARDI tracks how water diffuses through the brain's white matter - a way to measure the quality of myelin.

"HARDI measures water diffusion," Thompson said. "If the water diffuses rapidly in a specific direction, it tells us that the brain has very connections. If it diffuses more broadly, that's an indication of slower signaling, and lower intelligence. So it (HARDI) gives us a picture of one's mental speed."