External brain-drive. The randomest thought ever...

I guess it needs a brief (and boring) introduction first, i.e. why the hell this thing has crossed my mind. You see, I'm doing an MSc in high performance computing and as a part of my course I have to undertake a project. It's the same one I've been working on for my honours degree: optimising a neural map simulator. The software simulates visual cortex - a small part of the brain responsible for processing visual input. I remember asking once a PhD student from the group what were the goals of this kind of research, and one of them was, as he said, to find out how human memory works.

This made me think: so what if they succeed once? I'm quite sure that one day someone will make this discovery, it's just a matter of time. Given the current speed of development in technology this might even happen during our lifetime, of course if we don't nuke ourselves away by that point. Let's imagine for a second that someone has finally discovered and described all the processes happening inside a human brain. What's gonna happen next? Let's also imagine that they not only found out how it works but also how to interact with it: if brain can be described as a very powerful computer (i.e. it can compute stuff), then it must be possible to read data from it and write back. I cannot imagine the possible range of technologies that could be created based on that interaction! However, let's think about one of them: external hard-drives for brain (brain-drive!): the technology that allows recording memories on interchangeable microchips, thus greatly (possibly infinitely) extending the capabilities of rather limited human memory:

...
- Oh hey man! Long time no see, how's life?
- err. Hi! Who are you?
- Dude, I'm Fred. Fred from your 32 PetaByte blue Sony chip. You know, the one that has a sticker "friends and family" on it...
- Ok, just give me a sec. <...> oh, hey Fred!
...

I guess it would be very confusing to lose one of them. But let's go even further and imagine that would be possible to back-up all lifetime memories of one person on one of such "brain-drives", then wipe clean all memories of another (but not the first one!), and replace them with the backed-up data of the first person (update: adjusting all the biochemical processes inside that brain to make it an exact copy of the first one - don't think about implementation, just assume it's possible), just like you would dump all the data from your old PC hard-drive onto an external drive and then copy to a new one on a different PC: same files, new system.

Now, try to answer that:

• After such operation, would the recipient of memories be the same person as the donor?
• If the first person was you, which one of the two would be the you?

Apologies for this brainfuck, but I had to share.