The term in French is “plongeon rétrograde” which literally means “retrograde diving.” It refers to progressive memory loss in Alzheimer’s patients in which the person believes themself to be at a progressively earlier stage in life, having forgotten everything after that point. In other words, a woman will know her four older children but not her youngest; later she will only remember the eldest; later she will forget she has children at all and thinks she’s 20 and single. Do you know of a term for this in English? My usual terminological resources have proven ineffective.
It might be “temporally graded retrograde amnesia”. I’m not sure it’s the same thing tough. It when the further back you try to remember, the more vivid and easy to recall the memories become. So remembering what happened a year ago is nigh impossible, memories from early adulthood are more vivid, and memories from childhood are robust.
There is a graphic here that illustrates the way the memory recall work (or doesn’t).
If may help you research the terminology your are seeking though. I’ll try to ask a PhD in neuropsychology that I know. She probably knows the actual term you are looking for.