Perhaps you are remembering this scene from season 1, episode 3 "Time & Again"?
(The EMH is scanning Kes with his medical tricorder.)
EMH: Hmm. Hmm, hmm.
NEELIX: What?
EMH: Hmm?
NEELIX: Is something wrong?
EMH: Yes,
terribly wrong. Your brain is not on file. Either your government failed to transmit the standard fifteen five oh one crew personnel report or somebody at Starfleet Medical really fouled up.
KES: I'm not a member of the Starfleet crew.
NEELIX: We came aboard at mid-expedition.
EMH: And no one asked you for your medical histories when you arrived? Of course not. That would be the ship's doctor's job. My job, if anyone had bothered to tell me about new passengers, but I seem to be just about the last to know about everything around here. So, tell me, just how many other new arrivals are there?
NEELIX: Just us.
KES: And the crew from another ship that was destroyed.
EMH: Another crew. That's nice. This is the Emergency Medical Holographic system to Captain Janeway.
NEELIX: She's not on board. She's missing on the surface of a planet.
EMH: Missing. The Captain is missing. It seems
I've found myself on the Voyage of the Damned. Very well. Please advise the highest ranking officer who is not missing, to see me at his earliest convenience. You may shut off my program now.
NEELIX: But you haven't told us anything about her condition.
EMH: She is the healthiest member of her species I've ever seen. The only member of her species I've ever seen.
You have a lovely brain. It will make a fine addition to our files. I wouldn't worry. If your species has a history of extraordinary mental abilities, this may simply be your way of flexing those muscles for the first time. Living in space requires the body to make a variety of biological adjustments. This could be a side-effect of that process. Go home. Get a good night's sleep and drink plenty of fluids.
KES: Fluids?
EMH: Everybody should drink plenty of fluids. Don't leave without turning me off.
KES: Computer, end program.
EMH: And call me in the morning.
http://www.youtube.com/watch?v=ptVCjpX--18
[yt]http://www.youtube.com/watch?v=ptVCjpX--18[/yt]
You can usually find a clip of the part discussing
"I'm on the voyage of the damned"...in a quote compliation or tribute video, but I don't know about "the lovely brain" quote.
http://www.youtube.com/watch?v=KTgAjtGWtko&feature=player_detailpage#t=37s
