There's a book called Buddha's Brain that documents several studies of people meditating while being scanned by an fMRI machine. It's quite fascinating. Regular meditation alters connections in the brain, similar to how working out a muscle changes the muscle.

I was on the fence on whether claimed effects of meditation were real, and reading this book clinched it for me. It anchored the claims I'd read elsewhere in something I actually believe - fMRI scans of brain activity.