One reads more often than not that

and most sources seem to explain mechanisms of LTP that just last as long - from hours to days to weeks to months. Only rarely it is explicitly mentioned that such-and-such LTP lasts for years or a lifetime, and most authors seem to hesitate to make such claims.

But there are memories (and learned skills) that can be retrieved many years and even decades later, even though not (consciously) used in the meantime.

I have no idea how this kind of "really long-term potentiation" is explained. Three options come to my mind:

  1. The long-term potentiated synapses and the "memories" related to them have actually been used in the meantime (just "unconsciously" or in completely different contexts) and thus been re-newed and re-strenghtened every now and then.

  2. They degraded but have been re-newed without having been used, but by some other mechanisms than "normal" LTP.

  3. They actually did last for such a long time (i.e. didn't degrade) - and the authors just hesitated to claim it (because they could not prove directly).

Is one of these three explanations the correct one, or is there another one?

  • $\begingroup$ No time for an answer but some dendritic spines live long enough to sustain memories that can last for as long as the animal lives (Yang et al 2009). Each time a memory is recalled, it is also reshaped --potentially strengthened, attenuated, or otherwise altered. $\endgroup$ – vkehayas Jan 28 '20 at 21:20
  • $\begingroup$ @vkehayas. Hi, Vassilis, great to hear from you again! The explanatory problem is that a memory or skill (as a holistic entity) may be un-recalled for decades and thus not reshaped. It's only the synapses involved in the memory that are re-strengthened, attenuated, or otherwise altered - just by being part of many other memories that were recalled. Does this picture make sense? (Alternatively one might consider that the memory itself actually was recalled, but unconsciously, maybe in dreams?) $\endgroup$ – Hans-Peter Stricker Jan 29 '20 at 8:30

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