Stephanie Huwiler

Last Name

Huwiler

First Name

Stephanie

ORCID

0000-0001-8894-4871

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03963 - Wenderoth, Nicole / Wenderoth, Nicole

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Publications 1 - 10 of 10

The Potential Role of Sleep in Promoting a Healthy Body Composition: Underlying Mechanisms Determining Muscle, Fat, and Bone Mass and Their Association with Sleep
Stich, Fabia M.; Huwiler, Stephanie; D'Hulst, Gommaar; et al. (2022)
Neuroendocrinology
Sleep plays an essential role in human life. While sleep is a state elicited by the brain, its vital role reaches beyond maintaining brain health. Unhealthy sleeping habits have been associated with increased risk for inflammation, obesity, or diabetes. Evidence is emerging that sleep guides processes playing an important role in promoting the regulation of endocrine function involved in tissue regeneration and tissue remodelling. Thereby, sleep presumably is a critical factor contributing to the balance of core body tissues: bone, fat, and muscle mass. Given the increasing prevalence of various chronic diseases and comorbidities due to unhealthy lifestyle choices, sleep could be a key target to promote a healthy body composition up until old age. Here, we review the potential role of sleep and its underlying brain oscillations in body core tissues turnover. Specifically, we discuss potential underlying mechanisms linking sleep to body composition, both during rest and under challenging conditions. Among other described pathways, we highlight the possible role of the growth hormone that was found to be involved in the homeostasis of all core body tissues and has been strongly linked to brain activity dominating deep sleep, the so-called slow waves. Finally, we formulate important questions to be addressed in future research on the effect of sleep on body composition and specifically emphasize the importance of intervention studies to move from correlative to causal evidence.
Sleep and cardiac autonomic modulation in older adults: Insights from an at-home study with auditory deep sleep stimulation
Huwiler, Stephanie; Ferster, M. Laura; Brogli, Luzius; et al. (2025)
Journal of Sleep Research
The autonomic nervous system regulates cardiovascular activity during sleep, likely impacting cardiovascular health. Aging, a primary cardiovascular risk factor, is associated with cardiac autonomic disbalance and diminished sleep slow waves. Therefore, slow waves may be linked to aging, autonomic activity and cardiovascular health. However, it is unclear how sleep and slow waves are linked to cardiac autonomic profiles across multiple nights in older adults. We conducted a randomized, crossover trial involving healthy adults aged 62-78 years. Across 2 weeks, we applied auditory stimulation to enhance slow waves and compared it with a SHAM period. We measured sleep parameters using polysomnography and derived heart rate, heart rate variability approximating parasympathetic activity, and blood pulse wave approximating sympathetic activity from a wearable. Here, we report the results of 14 out of 33 enrolled participants, and show that heart rate, heart rate variability and blood pulse wave within sleep stages differ between the first and second half of sleep. Furthermore, baseline slow-wave activity was related to cardiac autonomic activity profiles during sleep. Moreover, we found auditory stimulation to reduce heart rate variability, while heart rate and blood pulse wave remained unchanged. Lastly, within subjects, higher heart rate coincided with increased slow-wave activity, indicating enhanced autonomic activation when slow waves are pronounced. Our study shows the potential of cardiac autonomic markers to offer insights into participants' baseline slow-wave activity when recorded over multiple nights. Furthermore, we highlight that averaging cardiac autonomic parameters across a night may potentially mask dynamic effects of auditory stimulation, potentially playing a role in maintaining a healthy cardiovascular system.
Get rid of the beat in mobile EEG applications: A framework towards automated cardiogenic artifact detection and removal in single-channel EEG
Chiu, Neng-Tai; Huwiler, Stephanie; Ferster, Maria L.; et al. (2022)
Biomedical Signal Processing and Control
Brain activity recordings outside clinical or laboratory settings using mobile EEG systems have gained popular interest allowing for realistic long-term monitoring and eventually leading to identification of possible biomarkers for diseases. The less obtrusive, minimized systems (e.g., single-channel EEG, no ECG reference) have the drawback of artifact contamination with varying intensity that are particularly difficult to identify and remove. We developed brMEGA, the first open-source algorithm for automated detection and removal of cardiogenic artifacts using non-linear time-frequency analysis and machine learning to (1) detect whether and where cardiogenic artifacts exist, and (2) remove those artifacts. We compare our algorithm against visual artifact identification and a previously established approach and validate it in one real and semi-real datasets. We demonstrated that brMEGA successfully identifies and substantially removes cardiogenic artifacts in single-channel EEG recordings. Moreover, recovery of cardiogenic artifacts, if present, gives the opportunity for future extraction of heart rate features without ECG measurement.
Auditory stimulation of sleep slow waves enhances left ventricular function in humans
Huwiler, Stephanie; Carro-Domínguez, Manuel; Stich, Fabia M.; et al. (2023)
European Heart Journal
Although the impact of sleep on cardiovascular health is widely accepted¹, precise mechanisms by which specific brain oscillations during sleep facilitate post-sleep cardiac function remain unclear. Slow waves, the prominent brain oscillations of non-rapid eye movement (NREM, here NREM Stage 2 + 3) sleep, are hypothesized to play a critical role in mediating the beneficial effects of sleep on cardiovascular functioning. Here, we used auditory stimulation to experimentally enhance slow waves and test whether that affects cardiovascular function during and after sleep.
Effects of auditory sleep modulation approaches on brain oscillatory and cardiovascular dynamics
Huwiler, Stephanie; Carro Dominguez, Manuel; Huwyler, Silja; et al. (2022)
Sleep
Slow waves, the hallmark feature of deep nonrapid eye movement sleep, do potentially drive restorative effects of sleep on brain and body functions. Sleep modulation techniques to elucidate the functional role of slow waves thus have gained large interest. Auditory slow wave stimulation is a promising tool; however, directly comparing auditory stimulation approaches within a night and analyzing induced dynamic brain and cardiovascular effects are yet missing. Here, we tested various auditory stimulation approaches in a windowed, 10 s ON (stimulations) followed by 10 s OFF (no stimulations), within-night stimulation design and compared them to a SHAM control condition. We report the results of three studies and a total of 51 included nights and found a large and global increase in slow-wave activity (SWA) in the stimulation window compared to SHAM. Furthermore, slow-wave dynamics were most pronouncedly increased at the start of the stimulation and declined across the stimulation window. Beyond the changes in brain oscillations, we observed, for some conditions, a significant increase in the mean interval between two heartbeats within a stimulation window, indicating a slowing of the heart rate, and increased heart rate variability derived parasympathetic activity. Those cardiovascular changes were positively correlated with the change in SWA, and thus, our findings provide insight into the potential of auditory slow wave enhancement to modulate cardiovascular restorative conditions during sleep. However, future studies need to investigate whether the potentially increased restorative capacity through slow-wave enhancements translates into a more rested cardiovascular system on a subsequent day.
Exploring the local field potential signal from the subthalamic nucleus for phase-targeted auditory stimulation in Parkinson's disease
Krugliakova, Elena; Karpovich, Artyom; Stieglitz, Lennart; et al. (2024)
Brain Stimulation
Background: Enhancing slow waves, the electrophysiological (EEG) manifestation of non-rapid eye movement (NREM) sleep, could potentially benefit patients with Parkinson's disease (PD) by improving sleep quality and slowing disease progression. Phase-targeted auditory stimulation (PTAS) is an approach to enhance slow waves, which are detected in real-time in the surface EEG signal. Objective: We aimed to test whether the local-field potential of the subthalamic nucleus (STN-LFP) can be used to detect frontal slow waves and assess the electrophysiological changes related to PTAS. Methods: We recruited patients diagnosed with PD and undergoing Percept™ PC neurostimulator (Medtronic) implantation for deep brain stimulation of STN (STN-DBS) in a two-step surgery. Patients underwent three full-night recordings, including one between-surgeries recording and two during rehabilitation, one with DBS+ (on) and one with DBS- (off). Surface EEG and STN-LFP signals from Percept PC were recorded simultaneously, and PTAS was applied during sleep in all three recording sessions. Results: Our results show that during NREM sleep, slow waves of the cortex and STN are time-locked. PTAS application resulted in power and coherence changes, which can be detected in STN-LFP. Conclusion: Our findings suggest the feasibility of implementing PTAS using solely STN-LFP signal for slow wave detection, thus without a need for an external EEG device alongside the implanted neurostimulator. Moreover, we propose options for more efficient STN-LFP signal preprocessing, including different referencing and filtering to enhance the reliability of cortical slow wave detection in STN-LFP recordings.
Auditory deep sleep stimulation in older adults at home: a randomized crossover trial
Lustenberger, Caroline; Ferster, Maria Laura; Huwiler, Stephanie; et al. (2022)
Communications Medicine
Background Auditory stimulation has emerged as a promising tool to enhance noninvasively sleep slow waves, deep sleep brain oscillations that are tightly linked to sleep restoration and are diminished with age. While auditory stimulation showed a beneficial effect in lab-based studies, it remains unclear whether this stimulation approach could translate to real-life settings
Functional role of sleep slow waves in cardiovascular health
Huwiler, Stephanie (2023)
Sleep is undoubtedly one of the most powerful mechanisms of the brain and body to recover. Although humans spend around one third of their life time asleep, only little is known about the specific processes through which sleep promotes overall health and well-being. During the transitions from wakefulness to sleep, and between the main sleep stages rapid-eye movement (REM) and non-REM (NREM) sleep, profound changes occur in brain oscillatory patterns and cardiovascular activity. The autonomic nervous system serves as a key regulator of these cardiovascular changes. While REM sleep is associated with increased sympathetic activity, NREM sleep promotes parasympathetic dominance, allowing the body to rest and recover from potential sympathetic overactivity accumulated during wakefulness. The hallmark oscillations of deep NREM sleep, the slow waves, are hypothesized to guide the proposed beneficial and cardio-protective effects of sleep, however, whether slow waves are functionally involved in cardiovascular function remains unclear. This PhD thesis aimed to address this research gap by applying the currently most promising method to specifically modulate sleep slow waves - auditory stimulation - and measuring cardiovascular parameters during sleep and postsleep. First, we investigated how different auditory stimulation approaches affect brain oscillatory and cardiovascular dynamics during periods of stimulation. We found a biphasic heart rate response and a temporary increase in blood pressure, likely caused by autonomic activation induced by evoking strongly synchronized slow waves in form of K-complexes. Furthermore, we demonstrated sound volume to have the potential to modulate the brain oscillatory response in a dose-dependent fashion. Next, we showed a robust improvement of left-ventricular function following one night of rhythmic auditory slow wave stimulation. Importantly, this cardio-beneficial effect was reproduced in a second independent night of slightly lower volume auditory stimulation. These findings suggest that slow waves are functionally involved in enhancing post-sleep cardiac function. Lastly, we explored the potential long-term benefits of auditory stimulation on cardiac autonomic regulation in healthy older participants, considering that aging is the main risk factor for the development of cardiovascular diseases. We observed distinct cardiac autonomic activity among participants who respond weakly and strongly to auditory stimulation. Because of the decreased baseline low slow wave activity levels in weak responders, these autonomic differences might be explained through a weaker subcortio-cortical synchronization ability in this group. Based on our findings, we propose that auditory stimulation modulates cardiovascular function by evoking K-complexes, which in turn organize brain-autonomic-body fluctuations through their strong brain synchronization potential and activation of central autonomic pathways. These fluctuations in autonomic activity may serve to stabilize the cardiovascular system during sleep and thereby enhance the arterial baroreflex, the body’s primary feedback loop for maintaining a stable blood pressure. Consequently, the enhanced coupling may improve cardiovascular regulation during sleep and increases cardiovascular function the next day. Altogether, the interleaved and bidirectional network of brain and cardiovascular activity during NREM sleep seems to be functionally involved in preserving cardiovascular health. While this PhD thesis provides first causative evidence of the involvement of sleep slow waves in increasing post-sleep cardiac function, further research is required to fully comprehend the mechanisms driving these favorable effects. Nonetheless, we highlight the potential of sleep stimulation and intervention in the prevention and treatment of cardiovascular diseases and its associated risk factors and thereby contributing to cardiovascular health up throughout the aging process.
Pupil size reveals arousal level fluctuations in human sleep
Carro-Domínguez, Manuel; Huwiler, Stephanie; Oberlin, Stella; et al. (2025)
Nature Communications
Recent animal research has revealed the intricate dynamics of arousal levels that are important for maintaining proper sleep resilience and memory consolidation. In humans, changes in arousal level are believed to be a determining characteristic of healthy and pathological sleep but tracking arousal level fluctuations has been methodologically challenging. Here we measured pupil size, an established indicator of arousal levels, by safely taping the right eye open during overnight sleep and tested whether pupil size affects cortical response to auditory stimulation. We show that pupil size dynamics change as a function of important sleep events across different temporal scales. In particular, our results show pupil size to be inversely related to the occurrence of sleep spindle clusters, a marker of sleep resilience. Additionally, we found pupil size prior to auditory stimulation to influence the evoked response, most notably in delta power, a marker of several restorative and regenerative functions of sleep. Recording pupil size dynamics provides insights into the interplay between arousal levels and sleep oscillations.
Overnight changes in performance fatigability and their relationship to modulated deep sleep oscillations via auditory stimulation
Carro-Domínguez, Manuel; Huwiler, Stephanie; Stich, Fabia M.; et al. (2025)
Journal of Sleep Research
Deep sleep oscillations are proposed to be central in restoring brain function and to affect different aspects of motor performance such as facilitating the consolidation of motor sequences resulting in faster and more accurate sequence tapping. Yet, whether deep sleep modulates performance fatigability during fatiguing tasks remains unexplored. We investigated overnight changes in tapping speed and resistance against performance fatigability via a finger tapping task. During fast tapping, fatigability manifests as a reduction in speed (or "motor slowing") which affects all tapping tasks, including motor sequences used to study motor memory formation. We further tested whether overnight changes in performance fatigability are influenced by enhancing deep sleep oscillations using auditory stimulation. We found an overnight increase in tapping speed alongside a reduction in performance fatigability and perceived workload. Auditory stimulation led to a global enhancement of slow waves and both slow and fast spindles during the stimulation window and a local increase in slow spindles in motor areas across the night. However, overnight performance improvements were not significantly modulated by auditory stimulation and changes in tapping speed or performance fatigability were not predicted by individual changes in deep sleep oscillations. Our findings demonstrate overnight changes in fatigability but revealed no evidence suggesting that this effect is causally linked to temporary augmentation of slow waves or sleep spindles. Our results are important for future studies using tapping tasks to test the relationship between sleep and motor memory consolidation, as overnight changes in objectively measured and subjectively perceived fatigue likely impact behavioural outcomes.

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Stephanie Huwiler

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