The amygdala encodes level of perceived fear but not emotional ambiguity in visual scenes

• Amygdala activity was modulated by perceived fear intensity.
• Amygdala activity varied proportionally with subject arousal ratings.
• Amygdala activity in complex visual scenes was not modulated by emotional ambiguity.
• Increased insula activity was found for stimuli with greater emotional intensity.
• Amygdala contributions to emotional evaluation extend beyond disambiguating stimuli.

There are two current models of amygdala functioning with regard to identification of emotional expression. Classic models propose that the amygdala contributes to emotional expression recognition and empathy by encoding the level of threat or distress, and as such, responds greatest to more potent fearful cues. However, recent evidence suggests that the amygdala directs attention to relevant object features to disambiguate the stimulus (e.g., the eyes of a fearful face). The present study used fMRI to investigate amygdala functioning during the perception and identification of emotion in complex visual scenes. Participants later rated the images on levels of fear, disgust and arousal. These ratings were used to identify stimuli that were emotionally-ambiguous, emotionally-discrete, and non-emotional for each individual. A whole-brain and ROI approach was used to identify the nature of the amygdala response to visual scenes. Amygdala activity was associated with higher levels of fear in stimuli and was found to reflect the level of arousal in complex visual scenes. In contrast, no activity was observed that would indicate that the amygdala was modulated by emotional ambiguity when discriminating between fearful and disgusting visual scenes. These results are consistent with models that implicate the amygdala in the evaluation and representation of the intensity of fear, and imply that the functional contribution of the amygdala to deciphering threat in visual scenes likely extends beyond the search for emotionally salient features. The results also suggest that using attention to remedy emotion recognition abnormalities in at-risk populations with amygdala dysfunction may not address all key deficits associated with contributions of the amygdala to emotion and empathy.