Sleep and dreaming in the light of reactive and predictive homeostasis

Neuroscience and Biobehavioral Reviews, Volume 147, April 2023, 105104

DOI: 10.1016/j.neubiorev.2023.105104

Péter Simora,b, Philippe Peigneuxb and Róbert Bódizsc

  • aInstitute of Psychology, ELTE, Eötvös Loránd University, Budapest, Hungary
  • bUR2NF, Neuropsychology and Functional Neuroimaging Research Unit at CRCN – Center for Research in Cognition and Neurosciences and UNI – ULB Neurosciences Institute, Université Libre de Bruxelles (ULB), Brussels, Belgium
  • cInstitute of Behavioural Sciences, Semmelweis University Budapest, Budapest, Hungary


Dreams are often viewed as fascinating but irrelevant mental epihenomena of the sleeping mind with questionable functional relevance. Despite long hours of oneiric activity, and high individual differences in dream recall, dreams are lost into oblivion. Here, we conceptualize dreaming and dream amnesia as inherent aspects of the reactive and predictive homeostatic functions of sleep. Mental activity during sleep conforms to the interplay of restorative processes and future anticipation, and particularly during the second half of the night, it unfolds as a special form of non-constrained, self-referent, and future-oriented cognitive process. Awakening facilitates constrained, goal-directed prospection that competes for shared neural resources with dream production and dream recall, and contributes to dream amnesia. We present the neurophysiological aspects of reactive and predictive homeostasis during sleep, highlighting the putative role of cortisol in predictive homeostasis and forgetting dreams. The theoretical and methodological aspects of our proposal are discussed in relation to the study of dreaming, dream recall, and sleep-related cognitive processes.

Keywords: dreaming; homeostasis; memory; mind-wandering; prospection; sleep.