Researchers are providing us some great insight into the most
   fundamental areas of learning and memory. Namely, we're now able
   to look at the small "spines" on the receiving end of the neuron
   (the dendrite). The latest research suggests that these spines
   are the location of memory. Interestingly, once the spines
   enlarge and stabilize, they don't go away from lack of use.
   Rather, their necks (the connection between the synapse and the
   dendrite) elongate. This elongation may account for forgetting.
   Interestingly, once a spine receives input after having been
   unused for a while, its neck immediately shrinks. This may be
   the mechanism for re-solidifying lost memory. So basically an
   unused "memory" biologically remains until it is needed again.
   And this may also happen with regards to the pointer-like neural
   network +[1]Adam Black*alluded to.
   [2][IMG]
   [3]KENNETH UDUT
   1:28 PM
   +[4]Edward Conrad* It makes sense - helps explain that "just out
   of reach" feeling with memories; they may LITERALLY be just out
   of reach, hiding behind a corner or a little ways down a tube. I
   like that idea because it can at least be tied to a physical
   system, something a lot of memory theories don't as they get
   lost in the world of mathematics and psychology and philosophy
   and such* (not that there's anything wrong with abstractions..
   but the way I look at it, those abstractions are happening
   someplace - in a brain at the very least :P ) When studying the
   brain a bit heavily last year, I was looking for analogies in
   physical systems, trying to find matches that were close enough
   to explain at least some things. The way rubber changes through
   vulcanization really struck me as helpful, as did the way that
   heat can release dyes (colors) and set dyes. There's a theory
   about how Anesthesia works that involves the nature of the brain
   matter itself (being fatty) - and the way that fats can congeal
   or liquify were also inspirational.* I never had any solid
   conclusions from my attempts at finding analogies for human
   memory but I did get some vague possibilities that I never
   fleshed out into any kind of full theories.

References

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   1. https://plus.google.com/108177944448520252638
   2. https://plus.google.com/116220525110856958463
   3. https://plus.google.com/116220525110856958463
   4. https://plus.google.com/108208849317759982392