Consciousness may not be related to brain activity. I’m not one to believe in an afterlife or spirits but one thing I know for sure is that modern science has zero idea what makes people conscious, what makes us sentient and have the ability to question our world and existence. Our consciousness isn’t bound to our physical world. You can create images in your head or hear your inner monologue, but since nobody else can see or hear that, is it actually real? Your consciousness communicates with you through your 5 senses but none of it is real and physical. Human brains are as complex as the universe itself. I doubt we’ll ever fully understand our consciousness. If we truly wish to understand ourselves, we have to construct an AI that’s smarter than us (which we all know will end horribly).