Biology subjects

Meissner, S. N.

Publications and source records attributed to Meissner, S. N..

3 recordsLinked to original sources

bioRxiv2023

Pupil size reveals arousal level dynamics in human sleep

Recent animal research has revealed the intricate dynamics of arousal levels that are potentially crucial for maintaining proper sleep resilience and memory consolidation. Also in humans, changes in arousal level are believed to be a determining characteristic of healthy and pathological sleep but tracking arousal fluctuations has been methodologically challenging. Here we measured pupil size, an established indicator of arousal levels, during overnight sleep and tested whether the arousal level affects cortical response to auditory stimulation. We show that pupil size dynamics change as a function of sleep macrostructure and microstructural events. In particular, pupil size is inversely related to the occurrence of sleep spindle clusters, a marker of sleep resilience. Additionally, pupil size prior to auditory stimulation influences the evoked response, most notably in delta power, a marker of several restorative and regenerative functions of sleep. Recording pupil size dynamics provides novel insights into the interplay between arousal levels and sleep oscillations, opening new avenues for future research and clinical applications in diagnosing and treating pathological sleep associated with abnormal arousal levels.

neuroscience↗

bioRxiv2023

Theta and alpha EEG oscillations reflect sleep need -- except during the wake maintenance zone

Increasing time spent awake results in accumulated sleep need, a process known as sleep homeostasis. Sleep homeostasis combines with a 24 h circadian rhythm to determine when and for how long we sleep. Both sleep homeostasis and the circadian rhythm substantially affect spectral power of the wake electroencephalogram (EEG), but not in ways predicted by current models. Specifically, these models hypothesize that time spent awake increases neuronal synaptic strength, which increases synchronization and should therefore increase oscillatory activity. However, the dominant wake EEG oscillations, measured as theta (4-8 Hz) and alpha power (8-12 Hz), do not follow the predicted buildup in homeostatic sleep pressure with time awake. This is due to a limitation of spectral power analysis, which does not distinguish between changes in the amplitude of oscillations from changes in the quantity of oscillations present in the signal. We wished to determine whether the amplitudes of EEG oscillations would specifically reflect homeostatic sleep pressure, independently from changes in quantity. We collected data from 18 young healthy adults during a 4-h sleep / 24-h extended wake paradigm. We indeed found that theta and alpha oscillation amplitudes reflect homeostatic sleep pressure, increasing along a saturating exponential function with time awake. Instead, theta quantities increased linearly with time awake, and alpha quantities decreased. Notably, theta and alpha amplitudes temporarily decreased during the wake maintenance zone (WMZ), a 3-4 h time window just before bedtime when it is difficult to fall asleep. Using pupillometry, we also found that mean pupil diameter increased during this window, while variance decreased. These results suggest that the WMZ is dependent on an alerting signal from the ascending arousal system. The WMZ therefore counteracts the observed build-up in homeostatic sleep pressure reflected in EEG amplitudes by temporarily desynchronizing cortical activity.

neuroscience↗

bioRxiv2022

Through the eye to the brain: Modulating LC-mediated arousal via pupil-based neurofeedback

The brains arousal state is controlled by several neuromodulatory nuclei known to substantially influence cognition and mental well-being. Here, we investigate whether human participants can gain volitional control of their arousal state using a pupil-based biofeedback approach. Our approach inverts a mechanism suggested by previous literature that links activity of the locus coeruleus (LC), one of the key regulators of central arousal, and pupil dynamics. We show that pupil-based biofeedback enables participants to acquire volitional control of pupil size. Applying pupil self-regulation systematically modulates activity of the LC and other brainstem structures involved in arousal control. Further, it modulates cardiovascular measures such as heart rate, and behavioural and psychophysiological responses during an oddball task. We provide evidence that pupil-based biofeedback makes the brains arousal system accessible to volitional control, a finding that has tremendous potential for translation to behavioral and clinical applications across various domains, including stress-related and anxiety disorders.

neuroscience↗