One of Dr Clifford Saron’s short talks about his experience in working with Buddhist monks in Dharamasala to look at what happens to their brain activity whilst they are meditation. But as he says at the beginning of this video:
“…. maybe these meditators were always extraordinary people; maybe that extraordinariness was what had led them to meditation in the first place. So how can you test this scientifically? how do you set up a control group for people who’s already got 20, 30, 40 years experience of meditation?”
What they did was set up a longitudinal study called The Shamatha Project.