“Courage is resistance to fear, mastery of fear—not absence of fear,” wrote Mark Twain in the novel Pudd’nhead Wilson. “Except a creature be part coward, it is not a compliment to say it is brave.”
More than a century later, neuroscientists appear to have confirmed this view of human bravery in a brain-imaging experiment. In the June 24 issue of the journal Neuron, Uri Nili at the Weizmann Institute in Rehovot, Israel, and colleagues reported that a courageous act—bringing a snake close to one’s head, despite fearing it—was linked to elevated activity in a prefrontal cortex region known as the subgenual anterior cingulate cortex (sgACC).
“We think the sgACC contributes to courageous behavior by dampening fear-related bodily arousal, thus enabling the carrying out of an action despite subjectively experienced fear,” says Nili, who works in the laboratory of Yadin Dudai, principal investigator for the study.
Other studies have suggested that the same general area is important in regulating the emotional circuitry of the brain. This study appears to be the first to show that activity in this brain area is needed for a person to act despite a natural fear. It also suggests that therapeutic stimulation of the sgACC might help treat disorders related to excessive fear, such as post-traumatic stress syndrome and phobias.
“I thought the study showed a creative and interesting approach to investigating the neural mechanisms of overcoming fears,” says Mauricio Delgado, a neuroscientist at Rutgers University in New Jersey who wasn’t involved in the study but who has done a great deal of research on how the brain regulates emotions.
In the basic experimental setup, Nili and his colleagues placed a conveyor belt with a either a live snake or a cuddly toy bear (as a non-frightening control object), beside an fMRI machine. At set times during the experiment, the volunteer in the machine was to rate his or her fear level and also to press a button to move the conveyor-borne snake one step closer to his or her head. If the subject’s courage failed, pressing another button moved the animal one step farther away. [See a video of the experiment, including the snake, at Neuron's site.]
Nili and his colleagues studied 61 people in all, but focused most of their analysis on the 16 who were usefully part-coward, as Twain might have put it. Each of these “fearful retreaters” not only claimed to be afraid of the snake but also pushed the button to move it back seven or more times during the roughly hour-long experiment—so that on the occasions when he or she pushed the button to bring the snake closer, it did appear to represent an act of courage.
From the fMRI data, the researchers found that the increased activity of only one brain region, the sgACC, correlated with high fear levels during “advance” events but not “retreat” events—suggesting that this region was involved in the successful mastery of fear.
As sgACC activity increased, a common measure of fear- or stress-related bodily arousal, the sweat-related skin conductance response, went down , as did the fMRI-measured activity of several brain regions including the amygdala. The amygdala is connected to the sgACC and also helps to generate the body’s arousal when certain kinds of emotion, such as fear, are triggered. Nili and his colleagues think the sgACC probably helps the brain to overcome fear and perform appropriate actions by damping this fear-related arousal response—even when leaving the conscious experience of fear relatively unaffected—.
The researchers noted that the sgACC activity on average went up and stayed up when “advance” was chosen, but went up less and soon collapsed for “retreats” as if signifying the abandonment of the mental effort to overcome fear. Successful sgACC activity also tended to rise several seconds before the decision-period began. “We interpret this rise in activity as representing some form of preparatory mental bracing,” says Nili.
To Delgado, the study highlights the role of the sgACC not only in altering the brain’s representation of fear, as has been shown in previous experiments, but “in actually adapting to a fearful context and coping with negative emotions.”
Nili and his colleagues think that it might be possible to boost sgACC activity to help people overcome fear-related conditions. Researchers already have targeted the sgACC therapeutically with the technique known as deep brain stimulation, to alleviate drug-resistant depression. In this condition sgACC activity is abnormally high, and the treatment has involved reducing that activity. So it remains to be seen whether a fear-reducing boost to the sgACC would have a mood-depressing side effect.
“It’s another interesting area for research over the next few years,” says Delgado.