Genes Tied To IQ, Brain Size In UCLA ENIGMA Study

By: Stephanie Pappas, LiveScience Senior Writer
Published: 04/15/2012 02:17 PM EDT on LiveScience

Brain size and smarts are, to some extent, genetic — and now, a team of more than 200 researchers has uncovered specific genes that are linked to both brain volume and IQ.

Though scientists have suggested bigger brains are "smarter," this study is the strongest case yet for a genetic connection to brain size and to IQ. Of course, brain size is not 100 percent correlated with a person's intelligence, and other factors, including connections between brain cells and even a person's experiences, play roles.

"We found fairly unequivocal proof supporting a genetic link to brain function and intelligence. For the first time, we have watertight evidence of how these genes affect the brain," said lead researcher Paul Thompson, a neurologist at the University of California, Los Angeles, School of Medicine.

The international research team pooled brain scans and genetic data from around the world as part of a collaboration known as ENIGMA (Enhancing Neuro Imaging Genetics through Meta-Analysis). They scoured the data for single genes that influence disease risk as well as for genes linked to brain-tissue atrophy and brain size, said lead researcher Paul Thompson, a neurologist at the University of California, Los Angeles, School of Medicine. 

"Our individual centers couldn't review enough brain scans to obtain definitive results," Thompson said in a statement. "By sharing our data with Project ENIGMA, we created a sample large enough to reveal clear patterns in genetic variation and show how these changes physically alter the brain."

The genetics of brain size

With data from 21,151 people, the researchers were able to link specific genes to variations in brain size. Brains shrink naturally with age, but size is important in a number of mental ailments. Decreased brain volume marks disorders including Alzheimer's disease, depression and schizophrenia, the researchers report today (April 15) in the journal Nature Genetics. [10 Controversial Psychiatric Disorders]

For example, the hippocampus is the part of the brain linked to memory formation and organization. A gene sequence called rs7294919 on chromosome 12 is linked to variations in hippocampus volume: Every instance of a genetic variant called a T-allele in this region was linked to lower hippocampus volume equivalent to 3.9 years of aging. (DNA is made up of four bases — A, C, T and G.)

This location on the chromosome (a threadlike structure that holds a DNA molecule) occurred between genes associated with the regulation of cell death and with cellular brain development and the cleaning up of proteins, including tau, which becomes defective in Alzheimer's disease.

Size and smarts

Another notable genetic sequence, located within the HMGA2 gene on chromosome 12, was linked with intracranial volume — in other words, the space inside your skull that marks the outer limit as to how big your brain can get. At this spot, every C-allele variant was linked to not only lower intracranial volume, but also to lower IQ scores on the Multidimensional Aptitude Battery, a measure of intelligence.

"This is a really exciting discovery: that a single letter change leads to a bigger brain," said Thompson.

Going forward, Thompson said, researchers could start to figure out how to mediate these genes' influences on the brain. The genes influence brains across a wide subset of people (mostly of European descent) from North America, Europe and Australia. That means that drug therapies targeting these genes could have broad applications.

The researchers now plan to tackle the genes that influence the brain's wiring, hoping to unravel the secrets of connectivity-related disorders such as autism.

You can follow LiveScience senior writer Stephanie Pappas on Twitter @sipappas. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

• 10 Ways to Keep Your Mind Sharp
• Inside the Brain: A Journey Through Time
• 7 Ways the Mind and Body Change With Age

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PHOTOS: EINSTEIN UP CLOSE

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• Celebrated picture dated 18 march 1951,

  Celebrated picture dated 18 march 1951, shows German-born Swiss-US physicist Albert Einstein (1879-1955), awarded the Nobel Prize for Physics in 1921, sticking out his tongue at photographers on his 72nd birthday. AFP ARTHUR SASSE (Photo credit should read ARTHUR SASSE/AFP/Getty Images)

• Picture taken in Princeton in 19

  PRINCETON, UNITED STATES: (FILES) Picture taken in Princeton in 1931 of German-born Swiss-US physicist Albert Einstein (1879-1955), author of theory of relativity, awarded the Nobel Prize for Physics in 1921, playing the violin. Germany, the birthplace of Albert Einstein, launches 19 January 2005 a year of international celebrations to mark the 100th anniversary of three of the physicist's four papers that changed the way we view the Universe. AFP PHOTO/FILES (Photo credit should read -/AFP/Getty Images)

• German-born Swiss-US physicist Albert Einstein, au

  PRINCETON, : German-born Swiss-US physicist Albert Einstein, author of the theory of relativity, declares his opposition to the 'H' bomb and to the arms race between the USA and the USSR in a conference 14 February 1950 in Princeton during a TV broadcast which created a considerable stir in the United States and all over the Western World. (Photo credit should read AFP/AFP/Getty Images)

• Portrait taken 06 February 1938 at Princeton Unive

  PRINCETON, : Portrait taken 06 February 1938 at Princeton University of physicist Albert Einstein, author of theory of relativity. (Photo credit should read AFP/AFP/Getty Images)

• An undated portrait of German-born Swis

  An undated portrait of German-born Swiss-US physicist Albert Einstein (1879-1955), author of theory of relativity, awarded the Nobel Prize for Physics in 1921. (Photo credit should read -/AFP/Getty Images)

• An undated portrait of German-born Swiss

  An undated portrait of German-born Swiss-US physicist Albert Einstein (1879-1955), author of theory of relativity, awarded the Nobel Prize for Physics in 1921. (Photo credit should read -/AFP/Getty Images)

• Picture taken 10 February 1933 in El Mirador Hotel

  UNITED STATES: Picture taken 10 February 1933 in El Mirador Hotel in a California desert resort of Albert Einstein and his wife. (Photo credit should read AFP/AFP/Getty Images)

• Indian prime minister Pandit Jawaharlal

  Indian prime minister Pandit Jawaharlal Nehru visits physicist Albert Einstein at Princeton University 8 november 1949. Einstein, author of theory of relativity, awarded the Nobel Prize for Physics in 1921. (Photo credit should read -/AFP/Getty Images)

• Portrait of German-born Swiss-US physici

  Portrait of German-born Swiss-US physicist Albert Einstein (1879-1955), author of theory of relativity, awarded the Nobel Prize for Physics in 1921, celebrating his 75th birthay at Princeton University, march 15, 1954. (Photo credit should read -/AFP/Getty Images)

• Portrait taken in 1950 of German-born Swiss-US phy

  PRINCETON, : Portrait taken in 1950 of German-born Swiss-US physicist Albert Einstein (1879-1955), author of theory of relativity, awarded the Nobel Prize for Physics in 1921. (Photo credit should read AFP/AFP/Getty Images)

Comments

[Jeffrey Joe Miller]

06:55 PM on 01/21/2013

Brain size = smarter...oh pleeeze. That archaic dead horse again? An adequate understanding and definition of intelligence doesn't even exist yet. And i'm betting that the remaining scientists that do wholeheartedly support the "size matters" theory are 1. Men and 2. Also believe in the "might is right" theory. Guys, it ain't the meat, it's the motion and the quality of relationship and interaction.

[Mike2k12]

02:01 PM on 06/09/2012

If only there were a way to order society based on brain function, seems very logical next step.

[Imzadi]

08:39 PM on 05/05/2012

What this article failed to point out is relation to brain size. In many studies, a smaller cranium will house a brain with more convolutions, which ultimately has been demonstrated as the benchmark for intelligence.

http://www.dana.org/news/features/detail.aspx?id=11918

[Mathilda Jones]

09:10 AM on 06/09/2012

"which ultimately has been demonstrated as the benchmark for intelligence"

Really?

I read the article you linked to properly and that's not what it claims at all. It said...

By reviewing 37 neuroimaging studies, Haier and Rex E. Jung, a researcher at the Mind Research Network in Albuquerque, New Mexico, have developed a provocative theory that attributes human intelligence to a circuit that links the frontal lobes, which are involved in planning, organization and other highly developed human abilities, with the parietal region farther back in the brain, which integrates information from the eyes, ears and other senses. They believe this Parieto-Frontal Integration Theory, or P-FIT, best accounts for the evidence that intelligence depends on several brain regions tightly linked by axon tracks that form superhighways of information.

MRI studies typically put brain size/IQ relation at .4, which is pretty high. Bear in mind the brain doesn't just solve problems, a lot of it's mass is devoted to running your body, so the correlation isn't going to be 1. The MRI studies AFAIK also don't generally deal with a lean body mass to brain size, so the actual correlation for IQ and relative brain size would be higher than .4.

I can tell you no anthropologist is shy about telling you how homo sapiens got more intelligent as the relative size of it's brain increased.

[WheelsTurn]

02:48 AM on 04/30/2012

Well, cool! If your parents are smart, you're more likely to be smart!
.

I think people realize that. To be fair, this IS another step on a long road, but that's all. Don't save up for brain-boosting gene therapy yet, folks.

[drbillybob]

05:19 AM on 04/25/2012

Brain:Body mass is a fairly decent predictor of average intelligence in the races.

... although we are not allowed to talk about that.

[Imzadi]

08:40 PM on 05/05/2012

Or the exceptions...

:-)
\Hi, sweetie

[Mathilda Jones]

08:58 AM on 06/09/2012

What exceptions?

,

[tidalwave4455]

07:19 PM on 04/23/2012

Neanderthals had a larger brain to body ratio than Homo Sapiens, and their bodies were more robust. Baleen whales have larger brains than humans. Nuff said.

[drbillybob]

05:17 AM on 04/25/2012

Size matters ... within a species.

There is a very good reason why people are hesitant to accept that fact ... and I'll bet you can guess what it is.

[Mike2k12]

02:16 PM on 06/09/2012

whales don't have the layers or structure a human brain has.

Have a nice day.

[randomguy0083]

10:27 AM on 04/23/2012

"The genes influence brains across a wide subset of people (mostly of European descent) from North America, Europe and Australia."

No asians?

Also I can't wait for this to become
1) a free will vs determinist argument
2) eugenics
3) more random nonsense

[Debbie338]

11:36 AM on 04/19/2012

So, does brain size correlate to skull size? I wear a size 6 7/8 hat. Does that make me dumb?

[Wendy Marie Shull]

10:50 AM on 04/20/2012

I think you will be fine. I have met people who wear a size 8 hat and are as dumb as a box of rocks. When it comes to your brain, use it or lose it. Refer back to the part about brain tissue atrophy. Read something new everyday. Do a crossword or sudoku puzzle. Read a book, newspaper or a magazine. Learn a new skill or take a class.

As long as you are using your brain, you will be fine.

[drbillybob]

05:34 AM on 04/25/2012

Did Barry Bonds get smarter by juicing?

[eric14]

08:01 AM on 04/19/2012

Human brain is smaller than once was.

http://phys.org/news187877156.html

[Mike2k12]

02:15 PM on 06/09/2012

Guess you missed this part of the article:

"The researchers found that the Cro Magnon brain appears to have had a smaller cerebellum - the brain region linked to motor control and language - than our brains today. "

Oops maybe you should use your brain.

[eric14]

05:43 PM on 06/09/2012

Why be so rude when the article states:
''A new replica of an early modern human brain has provided further evidence for the theory that the human brain has been shrinking. ''

Did
I mention function or efficiency?
No. Then what? Size. What is wrong with you? Were you raised
by sarcastic sadists?

[TheIpsoFactory]

07:33 AM on 04/19/2012

The inequality taboo discussions apparently never will end.

1. Intelligence exists and is accurately measurable across racial, language, and national boundaries.
2. Intelligence is one of, if not the most, important factors correlated to economic, social, and overall success in the United States, and its importance is increasing.
3. Intelligence is largely (40% to 80%) heritable.
4. No one has so far been able to manipulate IQ to a significant degree through changes in environmental factors—except for child adoption and that they conclude is not large in the long term—and in light of these failures, such approaches are becoming less promising.

The USA has been in denial of these facts. A better public understanding of the nature of intelligence and its social correlates is necessary to guide future policy decisions.

[Hontas Farmer]

12:51 PM on 04/20/2012

In a world where disease resistance and predation are not factors it is even more important. Since intelligence is how we humans compete with eachother. We are now our own main competition. (Have been for quite a while too.)

[Franklin Robinson]

12:01 AM on 04/19/2012

for the love of god dont show this to the phrenologist

[Ngonyama]

10:46 AM on 04/19/2012

He would not understand: his brain is to small.

[waterycoffee]

06:35 PM on 04/18/2012

I like how they randomly mention that DNA has four bases.

[ccgndy]

08:39 PM on 04/18/2012

Yeah, in a double-helix model, it should be adenine pairing with thymine and guanine pairs with cytosine. AT-GC.

[methodman]

10:56 AM on 04/18/2012

You should write an article about how scope re-dimensions itself according to bulk. Also what are parts involved in size? How do algorithms change according to size? would be another interesting article.

[ccgndy]

09:57 AM on 04/18/2012

A brain that weighs five pounds have more IQ than a four pounder, I therefore conclude that bigger is better and small is terrible???.

[waterycoffee]

06:29 PM on 04/18/2012

Did you read the article? There are multiple factors that affect intelligence, not just brain size. Synaptic connections, your early family experiences, working memory size, information processing speed... there are tons of factors that haven't even been studied yet on a genetic basis

[Coldhandluke]

09:44 AM on 04/18/2012

Like we didn't know this already.