Dreaming and REM-sleep: History of a scientific denial whose disappearance entailed a reconciliation of the neuroscience and the cognitive psychological approaches to dreaming
Since around 2010, important changes occurred in research on the neural bases of dreaming. From the 1960s until the end of the century, most sleep physiologists and some dream researchers continued to adhere to the view that rapid eye movement (REM) sleep was the functional state of the brain concomitant to dreaming, in spite of numerous published findings falsifying that view. At the beginning of the 21st century only, the idea that the neural basis of dreaming is not REM sleep was accepted by a new generation of sleep physiologists. The present article firstly presents how the REM sleep hypothesis of dreaming originated in the 1950s and became the received view on the neurophysiological bases of dreaming. Secondly, five categories of counter-evidence published during the following decades are summarized. The next section recalls the long-lasting denial of the body of counter-evidence. The Discussion section starts with two cognitive topics: dream recall and the definition of dreaming. We then discuss the relationships between the neuroscience and the cognitive-psychological approaches to dreaming. The main categories of current experiments on the neural bases of dreaming are then presented. They show that giving up the received view permitted neuroscience research on dreaming to enter a new era. The last part of the article proposes an explanation of the scientific denial by the psycho-physiological reductionism of many sleep specialists of the time. The main drawbacks of a reductionism stance are listed and the article ends on a lesson to draw from this historical episode.