Because the researchers know exactly how all the monkeys in their colony are related, they were able to trace the inheritance of anxious behaviors through the family tree. They found that 35 percent of the variation in anxiety could be explained by the genes passed down by mom and dad.
But the researchers took this finding one step further. They looked at specific brain regions that activated during stressful situations, and then matched those up with brain regions whose structure and function were inherited in the same pattern as the anxiety. They found that structure did not seem to affect an anxious temperament. But the function of three brain regions was both heritable and involved in anxiety.
The first, the orbitofrontal cortex, sits behind the forehead and is the most evolutionarily advanced part of the brain, Kalin said. The next was the amygdala, an almond-shaped region deep in the middle of the brain that is involved in fear and emotion. The third was the limbic system, which sits at the very base of the brainstem and is a part of even the most primitive reptile brains.
"What we find is more activity" in the anxious brains, Kalin said. It's as if the parts of the brain that have evolved to deal with normal threats have gone supercritical, responding to mild threats as if they were major, he explained.
"This now focuses us on very early childhood, to be thinking about alterations in brain function in children and ideally to be developing ideas that are new about what we can do to help kids that have this brain overactivity," Kalin said.
The next step is to continue using rhesus monkeys to understand the brain systems and molecular interactions that lead to hyperactive fear regions, he said. The researchers are also following young children over a period of years, scanning their brains to determine what makes the difference between the half of anxious-temperament children who develop a mental disorder and the half who don't. A separate line of research has already found that a secure attachment to a caregiver helps prevent later mental disorders for extremely shy kids.
"These are very serious illnesses that are common and affect lots and lots of the population," Kalin said. "We need to understand better what causes them, what the genetic underpinnings are and come up with new treatments to reduce suffering and hopefully do this early in life.
Address: 5636 Lemon Ave.
Dallas TX 75209
Phone: +1 214 5203694