And eventually, via participation in a live functional MRI scan, I discovered that at least in my case, I’m using different areas of my brain when I write with a pen on paper, when I write as a paleographer and when I keyboard.
Are you stuck on a piece of writing?
Here's a simple solution. Change the way you write.
Write by hand if you usually write on your computer. Write on an iPad if you have one. Write on your smart phone's dinky screen. Write on a LARGE piece of paper (I'm addicted to Oasis pads, they're huge).
It doesn't matter much how you change your writing method, just change it.
Changing the way I write ALWAYS gets me unstuck, and I've found that that's true for my writing students too.
Try it yourself, and see.