I don't believe our consciousness ceases to exist. I believe it is transferred into another realm. Energy cannot be created or destroyed it merely changes forms. It was here since the beginning of the universe and will be for however long. I believe it's the same with consciousness, it will get transferred into another lifeform after it has done its time in the afterlife. That form might be plant, animal, or human depending on karma. And after that again, and again and so on.