Training for Nirvana?

Came across this speech at NYTimes blogs. A brain scientist gets a brain strokes, recovers and talks about it.
One of the points she mentioned was that with her controlling the body part of brain shutting down she had almost a euphoric sensation for a while. She is detached from her own body- viewing it as some separate machine.
I've always wondered what do these yogis, mystics talk about when they talk about dhyan and euphoria and detachment from physical world. Is it that what the meditation unwittingly unlocks is a switch that shuts the rational mind off for a while leading to such an experience we often talk in terms of 'revelation', out of body experience, communion with God etc?