Mediating Effect of Amygdala Activity on Responses to Fear vs. Happiness in Youths with Disruptive Mood and Behavior Disorders

Irritability, characterized by a tendency to exhibit increased anger, is a common clinical problem in youth. This study investigated relationships among irritability, selective impairment in process of facial emotion, and neural responses in amygdala in youth with irritability during implicit emotion processing task under functional MRI (fMRI). Fifty-nine youths with disruptive mood and behavior disorder completed a facial expression processing task with an event-related fMRI paradigm. We found a positive relationship between irritability and RT difference between negative (fear) and positive (happiness) facial expressions. Increased irritability was associated with a longer reaction time toward positive vs. negative facial expressions. Irritability was also positively associated with the difference of amygdala blood oxygen level dependent responses between the two emotional conditions (happiness > fear). This difference in amygdala activity mediated the interaction between irritability and the RT difference between negative and positive facial expressions. We suggest that impairment in the implicit processing of facial emotional expressions with different valences causes distinct patterns of amygdala response, which correlate with the level of irritability.