Really cool models of the skull and brain!
I'm assuming your game is rendering these on the fly. Because they're so detailed, yeah that polygon count is going to kill your performance.
Since your game is basically just showing animations, I would just create and play those instead of trying to have Unity move the objects/camera and render lighting in real-time.
For example, if I make a GIF of just this scene:
This short GIF clip is only 446k. The Mp4 version was only 130k.