Medical animation

I took your 1-day course today in Boston and it was wonderful! My area is the production of animations for explaining novel and/or complex medical/scientific ideas. Examples include mechanism of action of drugs at the cellular/molecular levels, function of medical devices, and drug delivery. I’d very much appreciate if you could answer the following questions:

1. When is animation a better solution compared to a still image, or even a series of still images? When is 3D animation better than 2D animation?

2. Is there any evidence that visual explanations are superior to other modes (text, voice) in terms of understanding, retention, or preference by learners?

3. Can you refer me to a review or book on the use of animation in scientific visualization?

Thanks very much!