Jelena Skorucak

Scientific Reports

Acoustically evoked K-complexes together with sleep spindles boost verbal declarative memory consolidation in healthy adults

Sven Leach, Elena Krugliakova, Georgia Sousouri, Sophia Snipes, Jelena Skorucak, Selina Schühle, Manuel Müller, Maria Laura Ferster, Giulia Da Poian, Walter Karlen & Reto Huber

https://www.nature.com/articles/s41598-024-67701-7#citeas

Over the past decade, phase-targeted auditory stimulation (PTAS), a neuromodulation approach which presents auditory stimuli locked to the ongoing phase of slow waves during sleep, has shown potential to enhance specific aspects of sleep functions. However, the complexity of PTAS responses complicates the establishment of causality between specific electroencephalographic events and observed benefits. Here, we used down-PTAS during sleep to specifically evoke the early, K-complex (KC)-like response following PTAS without leading to a sustained increase in slow-wave activity throughout the stimulation window. Over the course of two nights, one with down-PTAS, the other without, high-density electroencephalography (hd-EEG) was recorded from 14 young healthy adults. The early response exhibited striking similarities to evoked KCs and was associated with improved verbal memory consolidation via stimulus-evoked spindle events nested into the up-phase of ongoing 1 Hz waves in a central region. These findings suggest that the early, KC-like response is sufficient to boost memory, potentially by orchestrating aspects of the hippocampal-neocortical dialogue.

Sleep, Memory, Auditory stimulation, Closed-loop, Phase-targeted, K-complex, Acoustically evoked, Memory consolidation, Declarative memory, Verbal memory, Causality, Evoked spindles, Slow-wave-spindle coupling, High-density EEG

M21

Sleep

Neuromodulation by means of phase-locked auditory stimulation affects key marker of excitability and connectivity during sleep

Georgia Sousouri, Elena Krugliakova, Jelena Skorucak, Sven Leach, Sophia Snipes, Maria Laura Ferster, Giulia Da Poian, Walter Karlen, Reto Huber

https://academic.oup.com/sleep/article/45/1/zsab204/6347149

The propagating pattern of sleep slow waves (high-amplitude oscillations < 4.5 Hz) serves as a blueprint of cortical excitability and brain connectivity. Phase-locked auditory stimulation is a promising tool for the modulation of ongoing brain activity during sleep; however, its underlying mechanisms remain unknown. Here, eighteen healthy young adults were measured with high-density electroencephalography in three experimental conditions; one with no stimulation, one with up- and one with down-phase stimulation; ten participants were included in the analysis. We show that up-phase auditory stimulation on a right prefrontal area locally enhances cortical involvement and promotes traveling by increasing the propagating distance and duration of targeted small-amplitude waves. On the contrary, down-phase stimulation proves more efficient at perturbing large-amplitude waves and interferes with ongoing traveling by disengaging cortical regions and interrupting high synchronicity in the target area as indicated by increased traveling speed. These results point out different underlying mechanisms mediating the effects of up- and down-phase stimulation and highlight the strength of traveling wave analysis as a sensitive and informative method for the study of connectivity and cortical excitability alterations.

electrophysiology, slow-wave sleep, phase-locked auditory stimulation, slow-wave traveling

M21a

Scientific Reports

Automated analysis of a large-scale paediatric dataset illustrates the interdependent relationship between epilepsy and sleep

Skorucak J, Bölsterli BK, Storz S, Leach S, Schmitt B, Ramantani G, Huber R

https://pubmed.ncbi.nlm.nih.gov/37553387/

Slow waves are an electrophysiological characteristic of non-rapid eye movement sleep and a marker of the restorative function of sleep. In certain pathological conditions, such as different types of epilepsy, slow-wave sleep is affected by epileptiform discharges forming so-called "spike-waves". Previous evidence shows that the overnight change in slope of slow waves during sleep is impaired under these conditions. However, these past studies were performed in a small number of patients, considering only short segments of the recording night. Here, we screened a clinical data set of 39'179 pediatric EEG recordings acquired in the past 25 years (1994-2019) at the University Children's Hospital Zurich and identified 413 recordings of interest. We applied an automated approach based on machine learning to investigate the relationship between sleep and epileptic spikes in this large-scale data set. Our findings show that the overnight change in the slope of slow waves was correlated with the spike-wave index, indicating that the impairment of the net reduction in synaptic strength during sleep is spike dependent.

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M21

Frontiers in Neuroscience

Boosting Recovery During Sleep by Means of Auditory Stimulation

Elena Krugliakova, Jelena Skorucak, Georgia Sousouri, Sven Leach, Sophia Snipes, Maria Laura Ferster, Giulia Da Poian, Walter Karlen and Reto Huber

https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2022.755958/full

Sufficient recovery during sleep is the basis of physical and psychological well-being. Understanding the physiological mechanisms underlying this restorative function is essential for developing novel approaches to promote recovery during sleep. Phase-targeted auditory stimulation (PTAS) is an increasingly popular technique for boosting the key electrophysiological marker of recovery during sleep, slow-wave activity (SWA, 1–4 Hz EEG power). However, it is unknown whether PTAS induces physiological sleep. In this study, we demonstrate that, when applied during deep sleep, PTAS accelerates SWA decline across the night which is associated with an overnight improvement in attentional performance. Thus, we provide evidence that PTAS enhances physiological sleep and demonstrate under which conditions this occurs most efficiently. These findings will be important for future translation into clinical populations suffering from insufficient recovery during sleep.

auditory stimulation, non-rapid eye movement sleep (NREM), sleep homeostasis, recovery, slow waves

M21

Nature and Science of Sleep

Eyelid Closure Behavior of Patients with Idiopathic and Nonorganic Hypersomnia, Narcolepsy-Cataplexy, and Healthy Controls in the Maintenance of Wakefulness Test

Santschi, A., Schreier, D. R., Hertig-Godeschalk, A., Knobel, S. E., Herrmann, U. S., Skorucak, J., Wolfgang, J.S., Mathis, J.

https://www.tandfonline.com/doi/full/10.2147/NSS.S408318

Differential diagnosis of central disorders of hypersomnolence remains challenging, particularly between idiopathic (IH) and nonorganic hypersomnia (NOH). We hypothesized that eyelid closure behavior in the maintenance of wakefulness test (MWT) could be a valuable biomarker.

hypersomnia, hypersomnia associated with psychiatric disorders, excessive daytime sleepiness, vigilance test, central disorders of hypersomnolence, microsleep

M22