White dreams are made of colours: What studying contentless dreams can teach about the neural basis of dreaming and conscious experiences.

Reports of white dreams, the feeling of having had a dream experience without being able to specify this experience any further, make up almost one third of all dream reports, yet this phenomenon-until very recently-had not yet been in the focus of targeted investigations. White dreams are typically interpreted as forgotten dreams, and are sidelined as not being particularly informative with regard to the nature of dreaming. In this review article, we propose a paradigm shift with respect to the status of white dreams arguing that focusing on this phenomenon can reveal fundamental insights about the neural processes that occur in the dreaming brain. As part of this paradigm shift, we propose a novel interpretation of what white dreams are. This new interpretation is made possible by recent advancements in three different though interrelated fields focusing on dreaming, mental imagery, and wakeful perception. In this paper, we bring these different threads together to show how the latest findings from these fields fit together and point towards a general framework regarding the neural underpinnings of conscious experiences that might turn out to be highly relevant not just for dream research but for all aspects of studying consciousness.