iirc, Tesla, Newton and Nash all got "flashes of insight" which seemed to come from some source external to the self.
In my own experience, it certainly feels that way, and caused me to develop the idea of the familiar conscious mind, and another greater collective unconscious mind which encompasses the whole of the world.
From what I understand, the brain is simply an organ which performs the purpose of facilitating connections between things, rather than actually containing a person's mind it's self.