A lack of differentiation in amygdala responses to fearful expression intensity in panic disorder patients

Patients with panic disorder show abnormalities in threat processing and regulation, both on a behavioural and neural level. Better understanding of the underlying mechanisms could help to develop new treatment strategies. In this study, we investigated brain region activation in 18 patients with untreated panic disorder (PD) and 17 healthy controls (HC) during the processing of emotional faces with fearful, happy and neutral expressions, using functional MRI. The intensity of the expressions was either prototypically high, medium or low. PD patients showed significantly increased activity in the dorso-medial prefrontal cortex (dmPFC) in response to faces in general and specifically for happy faces. While HC showed a decreased amygdala response to medium/low fearful versus high fearful faces, this effect was not present in PD: amygdala activation was stable across all fearful faces in this group. Psycho-physiological interaction analyses indicated more negative connectivity between the amygdala and prefrontal areas in the PD group during the task. Amygdala activation in panic patients appears to be less sensitive to decreasing intensities of fearful facial expressions and salience monitoring areas were less active during fearful faces in general in this group. This suggests PD patients might avoid more extensive processing of fearful faces.