If you mention research just be prepared to discuss it in your interviews. They'll likely ask about it and by then you should have a decent grasp(after ~4 months or so in a lab) of what it's like. There's nothing wrong with mentioning career goals or what type of physician you see yourself being...just don't get tunnel visioned.
If you mention your desire to go into research and explain why(you like research, you want to help folks on a broader level, a specific disease needs better treatments, personal experience with it, etc.), then you'll be fine. You can mention what you've gained in your actual research experience once you have that experience in secondaries, interviews, and/or update letters.
