Nope. No one expects you to have a particular research area in mind or even a specialty. What's the secondary prompt? Just curious because it may not even be necessary to mention this unless the question specifically asks for it. In general, I think it's fine to say that you're interested in research but you haven't settled on a particular area. Alternatively, if there's anything that even remotely interests you, you can mention it and no one is going to hold you to it!
I think the general assumption is that premeds will change their minds and really none of this stuff needs to be decided until later on in medical school.