I wasn't aware that in Japanese anime the animation is done before the voice is recorded, which to me seems odd. But I do know that in western animation, the voice is always recorded before the animation. The voice actors are also recorded on video performing their facial and body expressions to help the animators. However, in addition to this, the animators use themselves as reference to act out the scenes their working on with either facial or body expressions. Take a look at behind the scenes of some Disney or Pixar animated films and sometimes you will see this being done. It's actually amusing to watch. Take a look at the making of Jurassic Park as another example, you'll see the animators acting like a herd of gallimimus to help them animate that particular scene. Very funny to watch!