Exploring and developing the concept of the dream as a threat monitoring-alerting mechanism

Summary. It is not clear that established dream theories adequately explain the purpose of something that accounts for such a substantial percentage of our time. Gewargis’s innovative theory - that dreams function to safeguard the organism during sleep - seems plausible and to have the potential to make an important contribution to a better understanding of why we dream. There are, however, a number of possible problems with it. In particular, the published literature is not used to substantiate the empirical claims upon which the theory is built; and this could be a major issue, as a some of these claims seem to be at variance with current scientific knowledge and/or to have limited face validity. This comment article draws upon the neurology literature to critique and suggest amendments to Gewargis’s theory; and proposes additional hypotheses relating to why and how dreams might act as a monitoring-alerting mechanism and protect the sleeper from a range of internal and external perturbations during REM and NREM sleep; and not just, as Gewargis appears to suggest, guard against inadequate blood flow to the brain or “oxygen-deprivation” to the lungs during REM sleep. A central argument in this comment piece is that to perform a range of functions, such as memory processing, the dream is where the sleeper’s consciousness is focused for much of the time asleep, and so it is also where the alerting-arousal messages need to be presented and processed during that time. In other words, and at variance with what Gewargis proposed, we don’t dream so as to provide a sleep defence mechanism, but a Dream Sleep-Defence Mechanism (DSDM) is needed because we dream. It addition, it argued that dreams - including through the use of broad categories (and, in particular, potential danger/not potential danger), rather than representational reflections of the reality in question - provide a cortical resource efficient mechanism. It is recognised, however, that support for a dream sleep defence mechanism is at best circumstantial and that the idea needs to be tested in experimental studies if it is to move beyond conjecture.