Meditation shifts brain function by reducing external sensory input.

“But for most people, it's going to involve stopping our movement, that is, not ambulating, not walking or running, so seated or lying down with eyes closed. When we do that, meaning when we sit or lie down and close our eyes, as trivial as that shift might sound to you, it actually is a profound shift in the way that your brain and other neural circuits in your body function for the following reason. When we close our eyes, we shut down a major avenue of what's called exteroception.”