"These findings have far-reaching implications because they help clarify how a balance of two important brain systems can influence an individual's behavior and emotional expression in times of need," says Ned Kalin, senior author on the study and chair of psychiatry at UW Medical School. "The findings suggest that how open an individual is willing to be in asking for help may depend more than we thought on how secure that individual feels at any given time in a supportive relationship."
The brain systems found to be involved were the amygdala, which is important in detecting and responding to threats, and the right prefrontal cortex, which plays a role in reaching goals and attaching to others.
The study will appear in the Proceedings of the National Academy of Sciences Online Early Edition during the week of March 7-11.
In monkeys and humans, it's natural to seek help from supportive individuals during trying times. Indeed, calling for help can be crucial to survival, says Kalin, a psychiatrist who has studied fear and social attachment in monkeys for two decades in an attempt to better understand anxiety and depression in humans.
However, since a cry for help also signals vulnerability - and, in the animal world, may attract the attention of predators - safety may depend on being careful about when to call out for help. The UW researchers wanted to know what brain systems determine why one individual is very comfortable expressing a need for help while another is much more restrained.
The brain-imaging study involved 25 rhesus monkeys that were separated from their cage mates for 30 minutes and made "coo calls," which function to recruit others for social support. Researchers measured the frequency with which each monkey called out, and then scanned each animal's brain with a special animal PET (positron emission tomography) scanner at UW-Madison's Waisman Laboratory for Functional Brain Imaging and Behavior. The high-resolution scans revealed metabolic activity in precise areas of the animals' small brains.
The scans showed that animals that called the most had more activity in the right prefrontal cortex and less in the amygdala. In contrast, those monkeys that called less frequently had less prefrontal cortex activity and more amygdala activity.
"Simply measuring brain activity in these two regions allowed us to predict with nearly 80 percent accuracy how much each individual monkey called for help," says Kalin.
The researchers were somewhat surprised to find reduced activity in the amygdalas of the most vocal animals, since increased amygdala activity is associated with fear and stressful states. It would be logical to expect that the animals that were most vocal would also be the most frightened.
"But in our earlier research, we showed that some monkeys will become inhibited and freeze when they're frightened, especially when a predator is nearby and the monkey believes that it hasn't yet been discovered by the predator," Kalin says. "We observed that the greater the fear, the less likely it was that animals would call for help, at least under certain circumstances. If you haven't been discovered by a predator lurking nearby, it's not a good idea to draw attention to yourself by crying out for help."
The situation may be very similar for humans, Kalin says, and may provide a framework for understanding differences in emotional expressivity.
"People who are less secure and more sensitive to potential threat are likely to have increased amygdala activity that may inhibit their urge to ask for help, which is related to right prefrontal cortex activity," he says.
On the other hand, he adds, "When a person feels safe enough in a relationship to express his or her vulnerabilities, this appears to be associated with a decrease in amygdala activity and an increase in prefrontal cortex activity. As relationships become more secure for the people involved, it's likely that changes in amygdala and prefrontal cortex activity may be responsible for the accompanying increase in sharing of intimate feelings."
Kalin believes that the degree to which a person may be willing to call for help probably depends on a variety of factors, including how frightened or threatened the person feels, what his or her general temperament is, the person's past experiences and what kind of social support system may be in place.
Collaborators on the paper include Richard Davidson, Andrew Fox, Terrence Olakes, Steven Shelton and Alexander Converse, all of UW-Madison.