Brain prioritizes threats, especially in anxious people.
New findings by French researchers show that the brain devotes more processing resources to social situations that signal threat than those that are benign.
The results in the journal eLife may help explain the apparent “sixth sense” we have for danger. This is the first time that specific regions of the brain have been identified to be involved in the phenomenon. The human brain is able to detect social threats in these regions in a fast, automatic fashion, within just 200 milliseconds.
Even more surprising for the scientists was the discovery that anxious individuals detect threat in a different region of the brain from people who are more laid-back. It was previously thought that anxiety could lead to oversensitivity to threat signals. However, the new study shows that the difference has a useful purpose. Anxious people process threats using regions of the brain responsible for action. Meanwhile, ‘low anxious’ people process them in sensory circuits, responsible for face recognition.
Facial displays of emotion can be ambiguous but the researchers managed to identify what it is that makes a person particularly threatening. They found that the direction a person is looking in is key to enhancing our sensitivity to their emotions. Anger paired with a direct gaze produces a response in the brain in only 200 milliseconds, faster than if the angry person is looking elsewhere.
“In a crowd, you will be most sensitive to an angry face looking towards you, and will be less alert to an angry person looking somewhere else,” says lead author Marwa El Zein from the French Institute of Health and Medical Research (INSERM) and the Ecole Normale Supérieurein Paris.
Similarly, if a person displays fear and looks in a particular direction you will detect this more rapidly than positive emotions. Such quick reactions could have served an adaptive purpose for survival. For example, we evolved alongside predators that can attack, bite or sting. A rapid reaction to someone experiencing fear can help us avoid danger.
“In contrast to previous work, our findings demonstrate that the brain devotes more processing resources to negative emotions that signal threat, rather than to any display of negative emotion,” says El Zein.
Electrical signals measuredin the brains of 24 volunteers were analysed while they were asked to decide whether digitally altered faces expressed anger or fear. Some faces displayed exactly the same expression, but the direction of their gaze was altered. A total of 1080 trials were carried out.
It has often been theorized that elevated anxiety, even in a non-clinical range, could impair the brain’s processing of threats. However, El Zein and her co-authors instead found that non-clinical anxiety shifts the neural ‘coding’ of threat to motor circuits, which produce action, from sensory circuits, which help us to recognise faces. The researchers note that it would be interesting to determine whether the same is true for people with anxiety scores in the clinical range.
Source: Zoe Dunford – eLife Image Credit: The image is in the public domain Original Research: Full open access research for “Anxiety dissociates the adaptive functions of sensory and motor response enhancements to social threats” by Marwa El Zein, Valentin Wyart, and Julie Grèzes in eLife. Published online December 29 2015 doi:10.7554/eLife.10274
Anxiety dissociates the adaptive functions of sensory and motor response enhancements to social threats
Efficient detection and reaction to negative signals in the environment is essential for survival. In social situations, these signals are often ambiguous and can imply different levels of threat for the observer, thereby making their recognition susceptible to contextual cues – such as gaze direction when judging facial displays of emotion. However, the mechanisms underlying such contextual effects remain poorly understood. By computational modeling of human behavior and electrical brain activity, we demonstrate that gaze direction enhances the perceptual sensitivity to threat-signaling emotions – anger paired with direct gaze, and fear paired with averted gaze. This effect arises simultaneously in ventral face-selective and dorsal motor cortices at 200 ms following face presentation, dissociates across individuals as a function of anxiety, and does not reflect increased attention to threat-signaling emotions. These findings reveal that threat tunes neural processing in fast, selective, yet attention-independent fashion in sensory and motor systems, for different adaptive purposes.
“Anxiety dissociates the adaptive functions of sensory and motor response enhancements to social threats” by Marwa El Zein, Valentin Wyart, and Julie Grèzes in eLife. Published online December 29 2015 doi:10.7554/eLife.10274