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Scientists have found a gene that may control whether or not someone is a risk taker. As this ScienCentral News video explains, the gene controls development of a specific part of your brain.
Thrill Seeking
Why does one person like to skydive or ski off cliffs while someone else is happy reading a book? After studying mouse behavior, scientists now have a clue into a certain gene that may be a factor.
Jim Olson of Seattle's Fred Hutchinson Cancer Institute led the team making the discovery. The gene, called neurod2, helps in the formation of a part of the brain called the amygdala. Olson says the gene, "Turns on all the other genes that are needed for a [stem] cell to become a nerve cell [for the brain] instead of some other kind of cell."
The amygdala is important in the process of thrill seeking because it is the part of that's brain central to your emotions and your ability to sense danger. It's designed to keep us out of dangerous situations by helping us store in our long-term memory moments that are especially frightening or emotionally stressful. Olson offers his own example of a negative emotional memory from scout camp: he describes counselors sounding a siren at all hours that signaled a water rescue drill. "For almost a year after that, every time I heard a siren I'd get sick to my stomach," he says.
The primitive, almond-shaped amygdala
Mice normally have two copies of the neurod2 gene. But Olson's team modified mice to have either just one copy or no copies of the gene. As they reported in the journal Proceedings of the National Academy of Sciences, they then studied the mice's behavior as compared with normal mice.
Since normal mice that have two copies of the gene like to hide in dark places, the scientists used two tests. In the first, the mice were placed in the center of an elevated metal "plus-shaped" platform. Two arms had high rails to let the mice hide. The other two had no rails. Olson says, "A normal mouse will go into the arms of the plus maze where they have… walls where they can be protected." But, he adds, "The mice that lack neurod2, particularly the ones who lack both copies of neurod2, will go out just as often into the walkways that don't have any protection."
In a second test the mice were placed in a box with two sections, one covered and dark, the other clear and light. Normal mice prefer the dark, but like the previous test, the mice without the normal number of neurod2 genes spent additional time exposed in the light side of the box. "These [modified] mice will just allow us to pick them up. They really don't have the normal fear responses," he says.
A fearless mouse
It's not likely that you'll find people without the neurod2 gene. For people, Olson says, "The more likely scenario is that the person might have a different gene sequence than other people… and those differences are what contribute to making some people behave or look different from other people… And I think that's where we might start to see some variations in human behavior — why some people are fearless and other people are very risk averse."
Of himself, his wife and snow skiing, Olson says, "I'm much more of a risk taker than my wife is and knowing that there might be a genetic basis for it helps to understand that… If you really just recognize that you are wired differently it becomes easier to deal with."
He says the next research step would be, "to take several hundred samples of DNA from a smattering of human beings." He'd then sequence the neurod2 gene to, "find out are they all the same or are there some differences?" If they find differences, they could then take a high risk-taker and a low risk-taker, sequence their genes, and use functional MRI studies to see if their brains respond differently to, for example, movies of skiing episodes, "and see if their brains respond differently to those exciting visual inputs," he says.
Ultimately, Olson hopes that in the next five to ten years, "that we'll have a much better understanding of the physiologic basis for why we take risks, why some people are risk averse, why some people are thrill seekers."
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