Background: Many individuals with borderline personality disorder (BPD) perceive emotional expressions in faces intended to convey no emotion and display a heightened sensitivity to facial expressions conveying threat, such as fear. In BPD, the amygdala activates in response to ambiguous and threatening facial expressions, although the differential sensitivity of this brain region to higher and lower intensities of fearful expressions and the relationship of this neural activity to personality impairments have not yet been investigated.

Methods: In the present study, we examined brain activation during an implicit facial emotion task with neutral faces and fearful expressions displayed at 50% and 100% intensity in patients with BPD (n=45) and healthy controls (HC; n=25).

Results: On neutral faces, higher brain activation was found in BPD compared to HC in the right temporal pole, amygdala, hippocampus, pallidum, and orbitofrontal cortex, whereas no significant whole-brain group differences were observed for either intensity of fearful expressions. A region-of-interest analysis focused on the amygdala-hippocampal complex showed greater activation for neutral and 50%-intensity fearful faces in BPD. Severity of personality impairment in the domains of empathy and identity were associated with higher precuneus activity during neutral and 100%-fearful face processing.

Limitations: Brain activation differences of this naturalistic severely ill inpatient sample may be influenced by comorbid Axis-I disorders often seen in samples of BPD.

Conclusions: These findings suggest a heightened amygdala-hippocampal response to neutral faces and moderate-intensity fearful expressions in BPD, while self and interpersonal impairments are associated with task-based activations in regions implicated in self-referential processes.