Heritage for risk taking?
Researchers led by James Olson from the Fred Hutchinson Cancer Research Center have found a gene that makes mice risk-taking. The gene product, a protein called Neuro-D2, affects the early development of the amygdala. Rodents with only one copy of the gene showed less fear than normal rodents.
The amygdala is the emotional center of the brain and plays a crucial role in emotionally shaped memories, which we tend to internalize more than experiences in emotionally neutral conditions. Researchers use these emotional memories to condition test animals: If a mouse receives a slight electric shock in connection with a sound, it will freeze in fear at every further sound due to the shock it experienced.
But not so with the test rodents used by Olson and his colleagues: The animals obviously didn't remember the bad experience at all and therefore didn't flinch at all. In another test, in which they were asked to choose between unsecured elevated walkways and paths with side walls, they made a purely random decision – the risk of falling didn't seem to bother them. Normal mice, on the other hand, almost exclusively prefer the safe paths with a wall.
The neuro-D2 protein signals stem cells to develop into nerve cells. As the researchers found when studying the brains of their rodents, the amygdala of animals with just one copy of the gene contained fewer neurons, and some areas were even missing entirely. Studies with mice without Neuro-D2 are not possible because the animals die a few weeks after birth.
In further investigations, the researchers now want to clarify what role the gene plays in humans.