The classic book on this subject is Zen and the Brain: Toward an Understanding of Meditation and Consciousness by James H. Austin - https://en.wikipedia.org/wiki/Zen_and_the_Brain and https://mitpress.mit.edu/9780262511094/zen-and-the-brain/ and http://www.zenandthebrain.com/

Be warned though; it is a huge, dense and detailed book since the author is both a neuroscientist/neurologist and a zen meditation practitioner himself.