Not sure what you're asking. I doubt if any answer provided by anyone, devout Christian, agnostic, atheist, or other religion would satisfy, based on your usage of the word concrete.
And "electrochemical activity in your brain" explains no more about consciousness than pretty colors on an MRI screen.
To the philosopher of science, that's what consciousness is. That our experience of consciousness "seems" different is no issue, what it is is just that. Electrochemical activity.
Consciousness is the fundamental aspect of existence.
And thereby, atheists and religionists are equally challenged to define what consciousness is. Which is why I originally asked you the question as to why this is is any more of an issue for the devout as it is the atheist.
So do you believe that your consciousness is the highest form of consciousness in the universe?