I would love to be as honest as possible, but even as an atheist I can't claim to know for certain. I know that I absolutely believe there is no god as far as god has been defined in any way that I've ever heard, and I really don't believe in any sort of spiritual afterlife - but I really can't claim to be certain that consciousness doesn't continue in some form. The difference between me and a theist, though, is that I don't make up fairy tales to fill in the gaps. I guess I would try to deal with it from a biological perspective and say that we'll never know for sure about the rest until we get there ourselves.
They go into a permanent sleep without the dreams and all the twitching! They don't remember what it was like before being born, so they won't remember anything after death! It balances itself out! They return to that wonderful energy of the sun so they can give life to the newborn animals. Works for people too!