It's been ingrained into us historically and culturally that we are something more than our brains, but that's not what the evidence suggests.
Is the sum greater than its parts when it comes to consciousness, or not? You cannot say that as of now, you don't know. There is not enough evidence to make that statement. There's not even an exact definition what consciousness/awareness/sentience is. Thus consciousness can't be measured either, otherwise there wouldn't be any debate about animals or artificial intelligence. Instead we could clearly say: this thing is conscious, this thing is not.
We are biased because, clearly, something is going on with us. But if you ignored for a minute that you KNOW that you are conscious, does outside evidence tell you that you are? Can you prove that another person has a consciousness and is not just a sophisticated drone running around? That is a distinction you cannot make for certain as of now. As stated, this is more a philosophical debate as of now. You can say that brain activity ceases, but you cannot say that brain activity is the root of consciousness. That one has not been proven.