I think I recall reading something about this as my mother has fallen foul of Alzheimer's.
Ramble

:
Your mind remembers just about everything, but it often takes a trigger or a like experience to bring it back, the ones that are clear are the events that you always keep front of mind, for some reason... as you age year by year the forefront of your brain retains the current and relevant, don't ask me how, but it does... With the dementia diseases areas of the brain get destroyed, therefore memories are never found, regardless of trigger points. Alzheimer's destroys the ability to store new info, then gradually eats back through time snaps.
Ramble over

Funnily I can clearly remember as a baby in a cot, in my parents bedroom waking up and seeing the red glow of a cigarette each, they were smoking in bed, in the dark... I also vividly remember laying in bed sobbing my heart out at not being a girl, right from a very young age, thinking about 4'ish, wanting god to wake me up in the morning as a girl and some nights laying there trying to pull my genitals off (I can picture the bedroom, bed covers, everything in so much detail... hence why I think it was about 4 as up till then I did not really see any differences until my girl cousin and I shared baths etc... could even have been 3, dunno!
But chunks of years I struggle to remember, hmmm Deja-vu?
The ability or magic of the brain is amazing, but I don't think GID or HRT affects it, however the jury is out as far as modern day living and the bombardment of additives, fumes and other such things.
Anyway that's my 2 cents worth, and all IMHO too
L Katy