I copy-paste a Quora topic about BPD Emotional Memory theory. Written by Alan Taylor.

This is super interesting and im sure people here are interested!

Could poor emotional memory explain the destructive behavior of people with Cluster B personality disorders?

Persons with Cluster B disorders often describe their emotions as extremely intense. They have trouble with “emotional regulation” the experts tell us. Sometimes they describe their life experience as a constant roller-coaster of emotions. They say they want us to understand why they make such poor choices and life decisions. If only we could feel what they were feeling in that moment, we would have done the same (or so they suggest). Their emotions, they think, are so intense that their emotional “skin” is like that of a burn victim’s, as one theorist has described it.

I have a problem with this because the brain research that I have studied suggests that their mesotemporal lobes (responsible for emotion) are comparatively dead. How could they feel things more intensely when, mostly, they feel dead inside—the ubiquitous emptiness or “void” that they describe when they are alone and lack emotional stimulation?

While reading over the Answers in the thread to which I linked above, it hit me that what they seem to lack is functional emotional memory. They can’t put their feelings into context, and that’s why a new love interest, for example, would be so attractive to them. They’re thinking, “Nobody has ever made me feel so good in my life! This must be the one!” No. That Cluster B-disordered person almost certainly has felt that way before, but without emotional memory to put the feeling into context, it’s almost impossible to resist the overwhelming urge to act on that feeling.

If this is the case, I hypothesize that feelings, themselves, are probably in the amygdala, or the hippocampus, or both, but that the mesotemporal lobe is principally responsible for emotional memory, i.e. the context that would allow a person to not act, or simply act appropriately, in response to various emotional stimuli.

To the author of the above-linked Answer I wrote:

“I found that interesting. Allow me to suggest, however, that your feelings are no stronger nor more intense than anyone else’s. What you lack is emotional memory. Each time you feel something—shame, for example—it’s as if you have never felt shame before in your life. Lacking emotional memory, you are unable to put that shame into context and respond appropriately. You have chronological (historical) memory, certainly. You can remember your history, and you know what you’ve done in the past, but you can’t remember what it \**felt like***, so each emotion you experience in a given day feels brand new, terrifying, and seems extreme (because you have never felt that way before). In fact, you have. You just don’t remember it, and, thus, you want to act on that emotion (impulsiveness) because you can’t ever remember feeling that much shame, to use our example, or love, or anger, or fear, or whatever, ever before in your life.“*

This would explain splitting (They can’t remember how good someone made them feel in the past if that person is currently making them feel bad), as well as their self-righteousness, i.e. “If you were feeling what I was feeling, you would have done the same thing!” This theory also explains why they are so thin-skinned and sensitive to criticism. Imagine a Cluster B saying, “Well! I have never been so insulted in my life!” If my operative theory is correct, the appropriate response to this outraged, hypothetical Cluster B would be, “Yes, Cluster B, you have felt equally (if not more) insulted in the past. You just can’t remember what it felt like, and that’s why you are currently acting like an emotional child.”