For decades scientists have tried, mostly in vain, to explain where intelligence resides in our brains. The answer, a new study suggests, is everywhere.

After analysing the brain as an incredibly dense network of interconnected points, a team of Dutch scientists has found that the most efficiently wired brains tend to belong to the most intelligent people.

And improving this efficiency with drugs offers a tantalising – though still unproven – means of boosting intelligence, say researchers.

The concept of a networked brain isn’t so different from the transportation grids used by cars and planes, says Martijn van den Heuvel, a neuroscientist at Utrecht University Medical Center who led the new study.


“If you’re flying from New York to Amsterdam, you can do it in a direct flight. It’s much more effective than going from New York, then to Washington, and then to Amsterdam. It’s exactly the same idea in the brain,” he says.

Intelligence indicator

Instead of airports, van den Heuvel’s team mapped the communications between tiny slivers of brain measured by a functional magnetic resonance imaging (fMRI) machine. Rather than scan the brains of subjects performing mental tasks, as most fMRI studies do, researchers took 8-minute-long snapshots of the brains of 19 volunteers, as they did nothing in particular.

The subjects’ brains, of course, didn’t go completely quiet, and the researchers reasoned that any brain activity they measured represented underlying connectivity between brain regions, near and far.

This allowed van den Heuvel’s team to build connectivity networks for each volunteer, and to measure the efficiency of each network. “It more or less reflects how many steps a [brain] region has to take to send information from one region to another,” he says.

This measure proved a decent predictor of each person’s IQ, explaining about 30 per cent of the differences between subjects, van den Heuvel says.

Intriguingly, the researchers found no link between the total number of connections in a subject’s brain network and their IQ. “We show that more intelligent people don’t have more connections, but they have more efficiently placed connections,” he says.

IQ boost?

Now that scientists are finally getting a grip on what features of the brain underlie intelligence, it may be possible to manipulate them, says van den Heuvel. “We’re looking at communication between brain regions, so why shouldn’t we be able to influence that?”

The first order of business will be to determine what physical and biochemical properties create more efficient brain networks. Other studies have shown that physical connections between brain regions via white matter that doesn’t contain neurons are also related to intelligence.

One recent report found strong evidence that these white matter tracts are inherited, and van den Heuvel’s team is now trying to determine if the same is true for functional brain networks.

“If it’s genetic, genes work through biology and, once we understand the biology, we have lots of ways to manipulate biology,” says Richard Haier, a neuroscientist at the University of California, Irvine. “In my mind, one of the important directions of this kind of research should lead to ways to improve intelligence on a neurochemical basis.”

Journal reference: Journal of Neuroscience (DOI: 10.1523/JNEUROSCI.1442-09.2009)