Tuesday, 26 April 2016

The Adaptive Role of Moderate Anxiety in Reacting to Social Threats

This post is by Marwa El Zein (pictured above), currently a postdoctoral researcher in the Social Cognition Group, based in Paris. In this post Marwa summarises her paper ‘Anxiety Dissociates the Adaptive Functions of Sensory and Motor Response Enhancements to Social Threats’, co-authored with Valentin Wyart and Julie Gr├Ęzes, and published in eLife.

I investigate the neural mechanisms of contextual influences during social perceptual decisions. Specifically, my work characterizes behaviorally and neurally how personality traits, past experience, and attention modulate facial perception.

In my paper, the adaptive role of moderate anxiety in reacting to social threats is put forward. Neural activity (electroencephalography, EEG) of participants was recorded while they categorized angry and fearful facial emotions. Individual anxiety of participants was assessed thanks to a personality trait questionnaire filled out at the beginning of the experiment (State-Trait Anxiety Inventory).

Importantly, the degree to which facial emotions were threatening to the observer varied through the manipulation of the emitter’s gaze direction (direct or averted toward the observer). Indeed, an angry person looking directly at you signals a direct threat to you (which is not the case if the same angry person was looking at someone else), whereas a fearful person looking aside signals a common (and unknown) threat in the environment.

First, we found that these combinations of gaze and emotion signaling threat enhance neural processing in visual and motor systems of the brain in a fraction of a second. Our findings demonstrate that the brain devotes more processing resources not to any display of negative emotion, but to negative emotions that signal threat. They add to theories according to which evolutionary pressure has shaped the brain to process signals of threat in a prioritized fashion to trigger rapid and adaptive reactions.

Second and interestingly, while anxiety of participants did not directly influence their behavior, it influences the neural processing of social threats. While low-anxiety individuals encode social threats in sensory (stimulus-selective) circuits, high-anxiety individuals encode threat signals in motor (action-selective) circuits. This double dissociation implies that elevated anxiety within a non-clinical range does not impair the processing of threat as often theorized. Rather, it shifts the neural 'coding' of threat to motor circuits in accordance with the adaptive function of anxiety: the rapid and adaptive reaction to threat.

The selective involvement of motor circuits in the processing of social threats in high-anxiety individuals is novel and surprising. Anxiety has been mainly associated with a non-selective 'over-sensitization' to threat. The observation that high-anxiety individuals are able to process signals of threat in a selective fashion in motor circuits of the brain puts forward a ‘positive’ and adaptive function of moderate, non-clinical anxiety in response to social threats.

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