Genetics plays vital role in intelligence

We could almost thank our parents for straight As or blame them for low standardized test scores, meaning that a big portion of our intellectual ability comes from our parents, according to research by Paul Thompson in the UCLA Department of Neurology.

Recently, Thompson has proven that the nature of brain wiring, which is present from birth, influences brain signaling speed as well as intelligence.

Since genetics influences brain structure, the genes we inherit play a far greater role in intelligence than was assumed in previous years.

The UCLA Laboratory of Neuro Imaging used a new brain scanner to show the positive correlation between intelligence and the efficiency of conducting messages by the brain’s axons. Axons can be thought of as wires that interconnect the brain, Thompson said.

The quality of the axons is determined by the myelin sheath, a fatty substance that wraps around the axons. It serves as an insulator of electrical messages, he added.

There is generally a higher Intelligence Quotient with more myelin, according to his article, “Genetics of Brain Fiber Architecture and Intellectual Performance,” which was published in the Journal of Neuroscience last month.

The greater the myelination, the stronger the water flow is in one direction in the axons, said Marina Barysheva, a research assistant in the Laboratory of Neuro Imaging.

High-Angular Resolution Diffusion Imaging, also known as HARDI, was used specifically to detect the amount of myelin in a brain by measuring the rate of water diffusion.

It is like Magnetic Resonance Imaging but with a higher magnetic field. It measures water diffusion in 105 directions at 8 million locations in the brain in 14 minutes, Thompson said.

Diffusion happens even when a person is at rest, so no specific task needs to be performed during the scan, Thompson added.

“I think one of the exciting things about the technology is you can use it … (to) look at the differences in IQ, and it’s kind of a controversial but interesting way of using brain scans to assess a persons IQ,” he said.

But researchers said we cannot completely depend on our parents for intelligence because the environment also plays an important role in our aptitude.

“The genes really define what your potential (of intelligence) is likely to be,” Thompson said. “(But) you need training, your learning and good, good education to really bring out the full potential.”

According to laboratory results, performance IQ correlates the most with the amount of myelin. Genetics mainly influences performance IQ, which is measured by tasks such as block design and picture completion, Barysheva said.

The genetics component explains families of politicians and athletes, said Dr. Liana Apostolova, a UCLA neurology professor and practicing neurologist.

“You have no option. … You’re drawn into that aspect,” she said, adding that this is the reason why children may act like their mother or father.

Intelligence research is not limited to intellectual capabilities. Brilliance measured in the brain is not restricted to classroom activities.

It is all of the experiences an individual has gone through. Your brain changes during every single new experience, including athletic and musical accomplishments, said Arthur Toga, a UCLA professor of neurology.

Though the pathways that the brain cells create stay constant, the amount of myelin changes, Barysheva said.

Aside from brain imaging, researchers say standardized test scores can be an accurate depiction of intelligence to some extent as well.

The MCAT and the GRE assess multiple types of mental abilities like math or logic and verbal skills. They are very well designed tests, Thompson said.

But some scientists say there can be flaws in standardized tests.

Intelligence is currently defined by a standardized IQ test in which the average score is 100.

But people should not get discouraged if they fall under 100 or become arrogant if they are above average, said Dr. Alex Leow, chief resident in geriatric psychiatry at the Neuropsychiatric Hospital of UCLA.

For example, if students become nervous on exams, they may not perform up to their real potential, Toga said.

Also, some people can be talented but may not succeed. They just need some luck in addition to motivation and stamina, Thompson said.

“IQ is quite important. It determines to some degree success and life and happiness and income,” he said. “(But) you can’t always predict how things come out.”

Though many aspects of intelligence are predetermined, there are still ways to take control, Thompson added.

“Learning and nutrition and diet and exercise all promote healthy brain function because they produce myelin production and mental speed,” Thompson said.