Abstract
Anxious individuals have a greater tendency to categorize faces with ambiguous emotional expressions as fearful (Richards et al., 2002). These behavioral findings might reflect anxiety-related biases in stimulus representation within the human amygdala. Here, we used functional magnetic resonance imaging (fMRI) together with a continuous adaptation design to investigate the representation of faces from three expression continua (surprise-fear, sadness-fear, and surprise-sadness) within the amygdala and other brain regions implicated in face processing. Fifty-four healthy adult participants completed a face expression categorization task. Nineteen of these participants also viewed the same expressions presented using type 1 index 1 sequences while fMRI data were acquired. Behavioral analyses revealed an anxiety-related categorization bias in the surprise-fear continuum alone. Here, elevated anxiety was associated with a more rapid transition from surprise to fear responses as a function of percentage fear in the face presented, leading to increased fear categorizations for faces with a mid-way blend of surprise and fear. fMRI analyses revealed that high trait anxious participants also showed greater representational similarity, as indexed by greater adaptation of the Blood Oxygenation Level Dependent (BOLD) signal, between 50/50 surprise/fear expression blends and faces from the fear end of the surprise-fear continuum in both the right amygdala and right fusiform face area (FFA). No equivalent biases were observed for the other expression continua. These findings suggest that anxiety-related biases in the processing of expressions intermediate between surprise and fear may be linked to differential representation of these stimuli in the amygdala and FFA. The absence of anxiety-related biases for the sad-fear continuum might reflect intermediate expressions from the surprise-fear continuum being most ambiguous in threat-relevance.
Highlights
Effects of anxiety upon representation of emotional expressions across the extended face network We looked to see if any region from the extended face network showed an anxiety-related adaptation “bias” for faces from the surprise-fear continuum that paralleled that observed in the right amygdala
Three expression continua were considered. Two of these contained expression blends generated by morphing between a face showing fear and the same identity showing either sadness or surprise
Our aim was to determine whether elevated trait anxiety would be associated with biases in representation in the amygdala of expressions containing some element of fear, and whether this would parallel biases in the perceptual categorization of these expressions
Summary
They signal emotional state and can act as warning signals that threat is imminent. Richards and colleagues examined the categorization of blended emotional expressions created by morphing between exemplars of basic emotions (Richards et al, 2002) They observed that high trait anxious individuals made more fear categorizations than low anxious participants for expression blends that contained 50% or higher proportion of fear, plus 50% or lower of surprise or sadness. Biases were not observed for other negative expression blends (e.g., anger/sadness) or for blends of surprise and happiness Based on these results, they hypothesized that categorization biases for expressions containing fear might reflect increased amygdala responses to such stimuli in anxious individuals
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call