I don't know a lot about biology or things like that, and this is probably a bit of a mess of a thought, but a lab grown brain in a jar could have some really interesting implications if given, say, a computer, as it's sensory inputs and ways of interacting with the world.

Would it know what it was? How might it socialize? What would it do on the internet? Would it understand the difference between real human controlled characters and AI characters in a video game? How effective might it be at learning our languages, and communicating with us in them? What might be the most effective way/medium for it to learn a language?

I think it would be really interesting to study, and I don't imagine there would be many ethical issues?