Whitehead argued that theories of consciousness often flounder because they explain what is most primitive and basic in terms of what stands out most clearly and distinctly. In contemporary times, a similar argument could be made that attempts to explain or understand experience in terms of it's more complex accomplishments (such as thought, computational ability, cognition, or language) are starting at the wrong place.
I agree with Whitehead that the starting point for understanding experience (whether conscious or unconscious) is in examination of our emotional, purposive and appetitive responses. In this respect, the sense of smell is of major interest.
Smell is the most ancient and primitive of the senses. The limbic system, the unconscious part of the brain that deals with motivation and emotions, developed from it. Thus, analysis of smell can give us an understanding of the most basic elements of experience accessible to our consciousness.
This is something I hope to explore further sometime. In the meantime, here is an interesting and accessible introduction to the sense of smell.