UI question re: panning camera behind

[Mad Jacq]

I'm using the Velious UI and love it. It's right back to the way I had it back in the day as far as I can remember with one exception...

I haven't been able to remember how to set things so I can use my mouse to dynamically look behind me as I am, for example, sitting or running.

I'm sure it's a simple fix and I am an idiot, but if someone could clue me in I'd be much obliged.