I was just having a discussion with a friend about this, as she asked me if my characters talk to me. I told her no, but there is a sense of the story taking over if you put enough time into planning the world, building your characters and your plot, and creating a good character dynamic. The author still maintains full control, but it almost feels like the story is writing itself as all the pieces you spent so much time preparing fall into place and even inspire new ideas to add further depth to what you'd already planned.

But no, no voices in the head, save for when I imagine the perspective character speaking out loud when I'm writing so I can see if it "sounds" right. Anything more than that, well...

I wonder if LKH knows there are medications for that.