Our body falls asleep, but the mind is still active. We are not in contact with the external world. The very fact that you can say, i slept like a log, i didn't know anything, points to the fact that there must have been a continuity of experience. That's why i say deep sleep is not an absence of experience. It's an experience of absence.
Question and Answer session lead by Swami Sarvapriyananda as part of a spiritual retreat at the Vedanta Society of New York on Mar 25th, 2018.