God made man in His image. Just as God is a three part God...God the Father, Son, and Holy Spirit. Man is in three parts as well. We have a soul (which is our mind, will, and emotions), spirit, and we live in a body. To answer your question...as long as the body is alive, the soul and spirit is still in the body as well. Our spirit man never sleeps and our soul is still active. The mind is conscious and then it has a subconscious. If a person is a vegetable we do not have the power to decide to take that life. God is the only one who can give and take life. When people are in comas they still hear. I have heard of situations where their spirit came out of the body and they were able to hear and see what was being said and going on. It is just amazing how God created us and the ability He put in man.