One theory holds that consciousness as we know/define it may be an external field, and therefore the human brain a radio receiver of some kind.
The real problem is that humans are easily fooled; so, true consciousness may never be achieved artificially. (Like the Turing test – Mind uploading may prove to be another Red herring.)
My own belief, in line with Buddhism, is that the individual personality (aka soul) is an illusion (a useful illusion), which is not to say there is no (eternal, constant) oversoul of which everyone is a part.