Yes, those are discussed medically, and in psychology as well. Look up limerance and cathexis in google.
Thats exactly what happened to H and I. He thought he no longer loved me. Or worse, that he never loved me at all. We started out as best friends, so that huge rush of feelings were played down.
When he met OW, he thought it was "Love". But a year later, he admitted that the feeling did not last. He even told me a month ago that he does not even miss her at all!
Me:49 H:45 D:12 M:14 T:18 Bomb: 6/26/10 EA: 9/3/10, fizzled out slowly, now ??? 11/5/11 Retrouvaille Finally piecing.... Its peaceful at last, but we got a looong way to go