Only two places asked about my undergrad research: Columbia and Penn.
Columbia was very interested in the work I did on calcium signalling. I didn't realize it as an undergrad, but this topic is very relevant to anesthesia. I think my interviewer was salivating until I told him I didn't remember exact results. I did that work 6 years ago and he was expecting me to remember very intricate details.... that was a little nuts. He wouldn't let it go, either. Don't worry.... I'm sure my experience at Columbia is rare at other places.
Penn asked about the research only because my interviewer knows my old research advisor. Then he said something along the lines of, "Don't worry.... I know nothing about that stuff, so we won't go there."
Several places I interviewed asked about my advance directive research. The conversation was generally benign. They usually asked about how I did the study and what I found. I gave them a two or three sentence synopsis. Then, they moved on to the next question. This is more the norm than my experience at Columbia.
A few places didn't even ask about my research at all. I think it's really unusual for them to ask about research before med school unless they have a specific interest in the work you did. Nevertheless, you should be prepared to talk about anything you put on your CV. Some interviewers like to play the game of asking about several random things on your CV. It could be anything from your hobbies to some activity in college.
