Does evidence support the claim that learning something new changes your brain for good, or that learning can be undone if you stop doing what you learned for long enough?

Answering this with proper science would easily take many books. Except in rare cases, simple answers cannot address the true nature of anything this dense. And yes, I realize I sound like a world-class know-it-all who is talking out of my butt-hole. Fair enough. So how would I look to answer these questions? Start with…