Why do some nights seem more restful than others, even when their duration is the same? A team of Italian researchers sheds unexpected light on this question. According to their recent work published in the journal PLOS Biology, the vividness of dreams plays a crucial role in the subjective perception of sleep quality.
This discovery challenges some common beliefs and could open up new therapeutic avenues for people suffering from sleep disorders.
A rigorous protocol carried out in the laboratory
The study was conducted by the IMT School for Advanced Studies Lucca in Italy. Forty-four healthy adults took part in the experiments, during which 196 nights of sleep were observed and analyzed in the laboratory. Throughout the night, participants were regularly awakened during dreamless sleep phases.
At each awakening, they answered two types of questions: the nature of their mental experience during sleep, and the level of restfulness they felt upon opening their eyes.
The results paint a nuanced picture. The deepest feelings of sleep were reported both after completely unconscious phases (with no perceptible mental experience) and after vivid and immersive dream episodes – even when brain scans indicated activity close to wakefulness. On the contrary, participants described their sleep as more superficial and fragmented during phases where they felt vaguely present, without truly dreaming.
The dream as a shield against brain fluctuations
To explain this apparent paradox, neuroscientist Giulio Bernardi, one of the study’s authors, puts forward a stimulating hypothesis: intense dreams act as a buffer against variations in brain activity, giving the sleeper the impression of deep sleep even when objective neural data do not confirm this depth.
The study focused on the NREM sleep stage N2 (without rapid eye movements), generally the longest of the night. The researchers observed that as sleep pressure decreases – meaning the physiological need to sleep diminishes towards morning – the vividness of dreams increases, along with the sense of having benefited from deep sleep. This phenomenon aligns with previous research associating REM sleep, characterized by strong brain activity, with more restorative subjective sleep reports.
Promising perspectives for treating insomnia
Beyond the fundamental understanding of sleep, these results offer a concrete therapeutic path. If future research establishes a causal link – something this observational study does not yet confirm – it could become possible to act on the quality of dreams to improve the sleep experience.
Controlled sensory stimulation, cognitive techniques, or pharmacological approaches: several avenues are already mentioned by Bernardi to modulate dreams and potentially help people suffering from insomnia or non-restorative sleep despite normal objective indicators.
SOURCE: ScienceAlert
