Naive realist answer: Nothing! The neural vehicles are completely independent of their phenomenal contents. By this theory, even my desktop computer, with its impoverished Boolean logic system, could possibly be experiencing a rich spatial experience of solid volumes, bounded by colored surfaces, embedded in a spatial void. Hell, even a ROCK or a SINGLE MOLECULE could be having spatial experiences that surpass the informaton content of a Gothic cathedral, or the ENTIRE UNIVERSE, for that matter. All bets are off! Any physical system can experience anything! There are no bounds!

Identity theory answer: You can't experience any more than your brain can explicitly represent.

Which one sounds more plausible?