It depends. If I'm "in the zone", there's nothing verbal about it. I stop seeing the screen or feeling the keyboard and the code just flows forth. I do have a mental imagery in the form of geometric shapes, but that's about it.
If I'm not "in the zone", then I verbalize a lot either with my actual voice or in my head, stating out loud what the immediate problem I'm solving is and walking through the steps I'm taking.