Selective Amnesia? Did He/She Really Forget Saying Those Awful Things?

 Imagine speaking, but not hearing or listening to your words, your tone, or your volume. Kind of like when you're wearing headphones and trying to talk to someone, and you shout but don't realize it. What if the words themselves that you are saying are also outside of your awareness, in the same way as the volume of your voice.
 You speak the words but don't have awareness or recall of what they were, or how they were spoken.
 This is the kind of processing many people with apparent narcissism have.
 The human brain is miraculous, but it's also limited, and it "kicks out" information that doesn't FIT with the "picture" of the world it has created and feels comfortable with. The normal human brain deletes information it doesn't "like" or agree with on a regular basis, as if it's just too much processing work to deal with the NEW information.
 This deleting process in people who are afflicted with Narcissism seems to be 'cranked up', so that they delete MORE information than people who don't have Narcissism. Their brain seems to simply rewrite the "story" to match how they want it to look and sound.
 So when a person with severe Narcissism is finished raging at a target, if and when the target expresses anger, sadness, or fear, the person with Narcissism often acts shocked or humiliated that the target is "IMPLYING" that their behavior and speech was not exemplary, well-mannered and logical.

This kind of deletion process can occur in people who have other issues such as severe stress or PTSD (or brain injury) and it can appear as Narcissism. It can also occur as a result of drug influence; as a brief example, most adults can recall a time where either they or someone they knew didn't remember clearly what they said or did (or at all) after having too much alcohol.

Since it seems that this deletion process is actually a brain "malfunction", this is yet another trait/behavior that appears to be neurological, not simply psychiatric, and therefore needs to be studied much more closely, and treated accordingly by health professionals.