It exists only statistically - information seems to be more like entropy than like energy. That's quantum mechanics. If you measure an atom to have spin up, it COULD be because it was alway spin up, or it could be that it was spin anything-but-down and you just got lucky. You might say "but since the fact that it was spin-x didn't affect the result, how do we know it existed at all?" Well, that's what bell's inequality is for, basically. The data in your brain isn't a hidden variable, it's part of the quantum state, and so is subject to being messed with when measured.