I'm interested in hearing what happens to memory from the axion and dendrite level outwards. Maybe faulty can do that. I know it from the other end.
The only way we know we have a memory is when we recall it, either explicitly or through changes in behavior. But, our memory does not actually exist as a stable entity...
Here's the funny thing:
The moment we recall a memory, we actually alter that memory. The more we recall it, the more likely that memory will be altered in some way. But if you only recalled it once, that first recall will be the more accurate representation of an actual event. Why is that? Because the act of recalling a memory exposes that "memory" to a new act of learning.
Example gratis:
EVENT
recall changes EVENT to Event A
subsequent recall changes Event A into Event Ab
subsequent recall changes it to Event Abc
Event Abcd
Event Abdce [note the change in order here]
Event Abdcef [which is subsequently remembered in the same order]
Event Abdcefg [and each new recall adds something to it maintaining the change in order]
Event Acefgh [notice that a key bit of information was dropped, the b]
So in the above example, the more you recall the information, the more embellishments, either accidental or intentional, you can potentially make that had nothing to do with the original EVENT. Did you notice that in the last recall, that
d was also dropped? If you didn't, that's one example of how your memory works (or doesn't work.) You don't notice certain changes.
The key to understanding this is that memory is not in any way stable. Just as learning is the process of memorizing, recalling a memorized event exposes it to new learning. In other words, you learn from your memories. This is how you are able to improve upon a piece you are practicing. The more you practice it (the more you recall it) the more changes you can make. In this case, the changes are intentional.
I don't know if I answered your question, though. You were asking for a physiological answer?
Synapses may not be permanent. According to most recent research into the behavior of axon terminals, it may make contact numerous times with a dendrite (or any other part of a neighboring neuron, possibly even itself) several times before it becomes stable and free-communicating. When it becomes stable, it can be described as a formed a memory. However, if that synapse is not used, the terminal may break contact on its own or, in the case of a highly stable connection, microglia (the terminators and trash collectors of the brain) will come along and prune that synapse.
Microglia roam the brain. It will extend its processes and make contact with synapses for several minutes. If it detects that the synapse is functioning, it will move on and find other synapses and repeat this process. If it detects that a synapse is defective or not used, it will remove it. Thus, this is one process of forgetting.
Microglia doesn't just prune damaged and unused synapses. It also destroys damaged and unused neurons. This is another process of forgetting.