BACKGROUND:

The amygdala has a central role in processing emotions, particularly fear. During functional magnetic resonance imaging (fMRI) amygdala activation has been demonstrated outside of conscious awareness using masked emotional faces.

METHODS:

We applied the masked faces paradigm to patients with major depression (n = 11) and matched control subjects (n = 11) during fMRI to compare amygdala activation in response to masked emotional faces before and after antidepressant treatment. Data were analyzed using left and right amygdala a priori regions of interest, in an analysis of variance block analysis and random effects model.

RESULTS:

Depressed patients had exaggerated left amygdala activation to all faces, greater for fearful faces. Right amygdala did not differ from control subjects. Following treatment, patients had bilateral reduced amygdala activation to masked fearful faces and bilateral reduced amygdala activation to all faces. Control subjects had no differences between the two scanning sessions.

CONCLUSIONS:

Depressed patients have left amygdala hyperarousal, even when processing stimuli outside conscious awareness. Increased amygdala activation normalizes with antidepressant treatment.