What about dreams? State of the art and open questions

Dream research has moved beyond the simple REM-NREM sleep dichotomy to focus on specific brain features that predict dreaming. Trait-like factors (stable personal characteristics) and state-like factors (electrophysiological activity just before awakening) both influence dream recall. Dreaming connects to waking life: the continuity hypothesis suggests dreams can be modulated by sensory stimulations. Parasomnia episodes may offer direct access to dream content, as recent findings show greater concordance between such events and dream narratives. Nightmares and oneiric activity hold potential clinical value in psychotherapy. Future work needs uniform protocols, advanced manipulation techniques, clarification of parasomnia-dream links, and determination of dreams' clinical relevance.

Study at a glance

Abstract

Several studies have tried to identify the neurobiological bases of dream experiences, nevertheless some questions are still at the centre of the debate. Here, we summarise the main open issues concerning the neuroscientific study of dreaming. After overcoming the rapid eye movement (REM) - non-REM (NREM) sleep dichotomy, investigations have focussed on the specific functional or structural brain features predicting dream experience. On the one hand, some results underlined that specific trait-like factors are associated with higher dream recall frequency. On the other hand, the electrophysiological milieu preceding dream report upon awakening is a crucial state-like factor influencing the subsequent recall. Furthermore, dreaming is strictly related to waking experiences. Based on the continuity hypothesis, some findings reveal that dreaming could be modulated through visual, olfactory, or somatosensory stimulations. Also, it should be considered that the indirect access to dreaming remains an intrinsic limitation. Recent findings have revealed a greater concordance between parasomnia-like events and dream contents. This means that parasomnia episodes might be an expression of the ongoing mental sleep activity and could represent a viable direct access to dream experience. Finally, we provide a picture on nightmares and emphasise the possible role of oneiric activity in psychotherapy. Overall, further efforts in dream science are needed (a) to develop a uniform protocol to study dream experience, (b) to introduce and integrate advanced techniques to better understand whether dreaming can be manipulated, (c) to clarify the relationship between parasomnia events and dreaming, and (d) to determine the clinical valence of dreams.