I know that lucid is when you're aware that you're dreaming and non-lucid is when you're not aware. But what I'm wondering is, what's the difference in our brains that makes us have lucid dreams? Because I barely do anything different from before I had LDs. Except for doing a reality check when I wake up and then maybe again sometime during the day and I write down my lucid dreams. Nothing else.

What happened inside my head that made the switch to make lucid dreams happen?
Have they done any sort of tests to see the difference (inside our brains) between a normal dream and a lucid dream? I mean, why is it that I realise that I'm dreaming nowadays, but before I didn't? How did I learn to do that?

Hope this makes sense.