This view is a rather new one, philosopher have argued about the mind-body problem for centuries. The brain is seen as something physical, while the mind is seen as something non-physical. Because of this distinction the mind always has been attributed with a lot of metaphysical qualities, e.g. being endless.

Today, where reductinism is the predominat paradigm, these terms are indeed used almost synonymously, which in my opinion is a little counter-productive, since it pushes the term "mind" even more away from its classical metaphysical meaning into a more esoteric domain.