Sleep and Biological Rhythms: from Cognition to Clinical Practice

The two-process model of sleep and wake regulation postulates that individual levels of alertness depend on the interactions between the accumulating homeostatic sleep pressure and circadian arousal signal. As a result of the complex interplay between these two factors, humans experience a great extent of intra- and interindividual variability in their cognitive and affective functioning. The proposed symposium offers comprehensive insights into the biological underpinnings of the discussed phenomena, utilising a broad range of neuroimaging (EEG, MRI, PET) and psychophysiological (pupillometry and salivary melatonin level assessment) methodologies. Starting with sleep-related processes, the initial three studies delineate variability in brain network organisation associated with accumulating sleep debt, and processing of endogenously and exogenously generated stimuli. In more detail, the presentations provide insights into the neural alterations associated with acute and chronic sleep deprivation, followed by neuroanatomical correlates of the frequency of experiencing lucid dreaming, and differences in region-to-region communication during auditory processing under wakefulness and varying levels of sleep depth. In turn, the remaining two talks focus on circadian rhythmicity, demonstrating the important role of external light processing in shaping the associated behavioural outcomes. The fourth presentation will probe the utility of salivary dim light melatonin onset (DLMO) and pupillometry-assessed retinal ganglion cell light sensitivity for diagnosis and phenotyping of delayed sleep-wake phase disorder. Last but not least, the final talk will demonstrate how the interactions of circadian and seasonal rhythmicity, as evidenced by variation in daylength and therefore light exposure, are reflected in the availability of dopamine and mu-opioid receptors, highlighting mechanisms potentially contributing to mood seasonality. As such, the symposium will deepen the audience’s understanding of the sleep- and circadian-related processes, demonstrating the wide variability of tools that can be used for studying the underlying biological mechanisms, together with potential clinical applicability of such knowledge.

The symposium includes presentations from 5 early career researchers: a postdoc (graduated in late 2025), a medical doctor (undergoing specialisation in psychiatry), and 3 doctoral students.