"Well, obviously that would require some work, in order for the uploaded individuals not to have to spend all their time in a featureless wasteland, but we've already got a lot of preexisting technology for connecting experiences to minds, mostly used for immersive fiction. Delivering experiences to an upload is almost certainly much easier than getting someone uploaded in the first place. Certainly all the tests will be on animals until we're extremely confident that uploaded people will not be better off dead. And if the virtual environment turns out to be very complicated or people simply don't prefer it, it should be likewise fairly straightforward to put them in robot bodies - or even figure out a way to clone blank brains and redownload them, although that's uncomfortably close to the current leading brand of functional immortality, which involves human sacrifice, and I'd want to be very sure no one would be tempted to take shortcuts with the downloading."