Leveling when playing in "downscaled" areas?

So I was wondering if you still level up while playing in the areas where your level is scaled down?

As an example. I'm level 45 and I go to a place where my level gets scaled down to 12 (or something). Will I still get proportionate amounts of experience points so that I actually level up, or do I get smaller amounts of xp like the "normal" level 12 people that will barely affect my progress?

Sincerely, AssCrust