Mirror neuron activations in encoding of psychic pain in borderline personality disorder

Borderline personality disorder (BPD) is characterized by pronounced emotional instability in interpersonal relations. Previous studies have shown increased activity in the amygdala, an imaging phenotype of negative affect. However, clinical accounts of BPD have drawn attention to deficits in social cognition and their likely role in engendering emotional instability. BPD patients show enhanced sensitivity to other people's emotions, while being less proficient in reading motives and reasons. In the present functional imaging study, we exposed BPD participants to stylized scenes of individuals affected by loss or separation, an issue to which these patients are particularly sensitive. Previously shown to activate the mirror neuron system, these mourning scenes were here also used to assess differential amygdala activity in stimuli of negative valence, but low arousal. Relative to controls, BPD patients were found to activate sensorimotor areas, a part of the mirror neuron system thought to encode basic aspects of the perception of motoric activity and pain. This contrasted with the activity of areas related to more complex aspects of social cognition, such as the inferior frontal gyrus. The amygdala was more active in patients when viewing these scenes, but this effect also showed a strong association with levels of depressiveness and neuroticism. After adjusting for these covariates, differences in amygdala activation were no longer significant. These findings are consistent with models of social cognition in BPD that attribute emotional sensitivity to emotional contagion through the mirror neuron system, in contrast to areas associated with more sophisticated forms of social cognition. These effects were accompanied by increased amygdala reactivity, consistently with the common occurrence of affective symptoms in these patients.