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 recently published work in the journal PLOS Biology, the vividness of dreams plays a crucial role in the subjective perception of sleep quality.
A discovery that challenges some conventional ideas and could open new therapeutic avenues for people suffering from sleep disorders.
A rigorous protocol conducted 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 degree of restfulness they felt when opening their eyes.
The results paint a nuanced picture. The deepest sleep sensations were reported both after completely unconscious phases (with no perceptible mental experience) and after episodes of vivid and immersive dreams – even when brain scans indicated activity close to wakefulness. In contrast, participants described their sleep as more superficial and fragmented during phases where they felt vaguely present, without truly dreaming.
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Dreams as a shield against brain fluctuations
To explain this apparent paradox, neuroscientist Giulio Bernardi, one of the study’s authors, proposes 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 N2 phase of non-rapid eye movement sleep (NREM), generally the longest of the night. Researchers observed that as sleep pressure decreases – meaning the physiological need to sleep diminishes towards morning – dream vividness increases, along with the feeling of having benefited from deep sleep. This phenomenon aligns with previous work associating the REM phase, characterized by high brain activity, with more restful subjective sleep reports.
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Promising prospects for treating insomnia
Beyond the fundamental understanding of sleep, these results offer a concrete therapeutic avenue. If future research establishes a causal link – which this observational study does not yet confirm – it could become possible to act on dream quality to improve the sleep experience.
Controlled sensory stimulation, cognitive techniques, or pharmacological approaches: several paths are already being discussed by Bernardi to modulate dreams and potentially alleviate insomnia or non-restorative sleep despite normal objective indicators.
SOURCE: ScienceAlert
