Largely the same.
The main reason for this is that, in my experience, the MD/PhD and MD interviews are often on the same day, in sequence. The truth is that the researchers you interview with probably wouldn't care if you were wearing jeans and a tshirt (which is what most of them wear), and you will feel overdressed stepping into their labs, but it's just a convention to dress up for the interview. All other applicants will be.
Having said that, I think I remember hearing that you already had your MD interviews, so I'm not sure how Minnesota does it, but I would certainly wear formal attire if I were you.
Have fun.