First up, I don't believe in "the soul" as some kind of separate component of any entity.
I believe "soul" is simply "the sum total of what makes me me" (or you you, etc). I think "soul" is a product of life, rather than the cause of it.
That said - memory is a very interesting subject to me for all kinds of RL reasons, so I have a few comments to this thread anyway.
simim23 Wrote:My question is: if our bodies have brains, and our brains hold our memories, if our "souls" just up and popped out of our bodies, leaving the shell behind, would the body retain these memories? Could one soul leave a body and have another one take its place, and still remember what was going on before it took over?
Could our soul's memories implant themselves in a brain, for any other future inhabitant to discover? 
If there is something my non-physical self remembers, and I sit and think about it here and now - then my physical brain is doing the thinking. As such, I think the act of recovering other-life memories does itself encode them into the physical brain. As for a soul up and leaving a body - given how I understand the concept of "soul" I don't accept the idea of a walking talking body without "a soul" in it anyway.
What I can answer, or at least speculate on, is what it would be like for the "left overs" if a fundamental part of that person became disconnected. I can discuss this because it has happened to me on a number of occassions, in my opinion as a direct product of the kind of multiple I am. When I am "disconnected" from the rest of myself, I still have access to all the memories I had when I was fully connected, but they seem irrelevant and meaningless.
Ever had one of those days where you have homework, or a work assignment, or something requiring thought to do - and even though you know it's not that hard, you simply cannot coerce your brain into working the necessary way to get it done? It's a little like that. I recall everything as normal, but I cannot/will not/do not actually *consider* it, because it is an irrelevance which I do not have the energy/ability/will to focus on.
The sensation is unpleasant.
It is also a form of dissociation (broadly - a set of mental phenomena in which you feel disconnected in some way from the world - that the world is not connected to you, that you as a person are not real, or that everything you experience is not real). I am sure this phenomenon can have purely physical reasons rooted in brain structure and chemistry (it certainly happens a lot to "regular" people to an extreme, and in a non-extreme form happens almost every day to almost everyone). As such I think it highly possible that "otherkin dissociation" is, rather than anything spiritual, just a product of some wayward brain chemistry; but that's a point for another thread.
Palmer Wrote:Personally, I think that brain-memories are based on fact, while soul-memories are based on emotion. They paint the same picture, but they're experienced differently.
Unless you're suggesting a metaphysical explanation for even regular day to day memory, then I disagree. (Even then, in fact!) Brain memories are very much based on emotion; there are in fact a number of specific and very strange disorders that result in, for example, a person being unable to attach emotions to visual memories.
The strangest of which is Capgras Delusion. This is a disorder in which the person believes that their close family and friends (sometimes all, sometimes just one) have been replaced by identical looking imposters, clones, or aliens. No amount of factual evidence to the contrary will shift the belief.
Best theory for the cause of this is that people with Capgras Delusion have damage to the emotional memory pathway. When they see a loved one they retain all factual memories of who that person is, but with absolutely no emotional response whatsoever. The only reasonable conclusion to "looks like my husband, but doesn't FEEL like him" is that it's not him, but an imposter.
Lots of strange stuff like this has been tied to specific physical areas of the brain. The human as a physical entity is not lacking in weirdness; quite the opposite in fact. Many truly strange and bizarre experiences have very physical causes.