A study, using an MRI, of BPD patients found:
We believe that this hyper excitability in BPD patients, particularly in brain regions thought to be involved in generating emotions, is likely to put this patient group at high risk for experiencing episodes of abnormally intense and inappropriate negative emotions characteristic of ED. In support of our hypothesis, we also found that the level of amygdala activation to the Fearful, and Neutral faces in BPD patients is significantly correlated with diagnostic measures of emotional lability.
So, what does this mean? If you “go calm” or “neutral” on the BP in your life, they will not understand it – their brain sees “neutral” as threatening.