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Adolescence is a particularly sensitive period of brain development during which a significant reorganization and breakdown of neuronal connections takes place. Various mental illnesses occur during this dynamic neuronal process. Close observation of these vulnerable processes could therefore be of great importance. There is good evidence that slow wave activity during sleep, an established measure of sleep depth, reflects the remodeling of neuronal connections (Tononi and Cirelli, Neuron 2014). Neuronal activity during sleep can be measured with relatively simple and inexpensive EEG measurements. Thus, important influencing factors such as motivation and momentary cognitive activity, which are particularly important in children or certain patient populations, can be bypassed.
In this research project, we are investigating such a clinical population using our methods. For example, we were able to show that children who meet the criteria for attention deficit hyperactivity disorder (ADHD) exhibit a reduction in slow waves during sleep compared to control children (Furrer et al., Transl Psych 2019).
We are currently applying closed-loop acoustic stimulation during sleep to achieve slow-wave amplification and investigate its effect on memory consolidation. The technology used was developed as part of a flagship project of the University Medicine Zurich in collaboration with the ETHZ and the USZ (SleepLoop | University Medicine Zurich | UZH)
We are pursuing two goals with our research project: Firstly, we want to show that disturbances in brain activity during wakefulness have an influence on slow-wave activity during sleep and thus contribute to our understanding of the function of sleep. Secondly, we hope that a modulation of brain activity during sleep will enable a causal influence on certain neuronal and cognitive processes. In particular, impaired memory consolidation during sleep is a target of modulation.
Sleep disorders are among the most sensitive early signs of various affective and psychotic disorders
( Tesler et al., Current Opinion in Psychiatry 2013).
Especially during adolescence, a highly dynamic phase of brain development, the complex interplay of sleep, thought and perception processes can become unbalanced. In the electrophysiologically measurable brain activity during sleep, the so-called sleep spindles appear to be elementary for maintaining sleep and consolidating certain learning content during sleep (Schabus et al., Sleep 2004; Manoach & Stickgold, 2019).
It has been shown that sleep spindles are reduced in people affected by psychosis compared to healthy people of the same age or compared to people suffering from depression (Ferrarelli et al.; American Journal of Psychiatry 2007; Gerstenberg et al., Schizophrenia Research 2020). This reduction in sleep spindles is associated with more intense cognitive impairment (Wamsley et al., Biological Psychiatry 2012). Cognitive impairments in particular are associated with a great deal of suffering and have so far been difficult to influence in therapy.
In adolescence, psychoses characterized by pronounced changes in thought and perception processes occur rather rarely. In contrast, less pronounced or fluctuating changes in thinking and perception are common at this age.
With the ongoing research project «Schlaf Dich Wach(notion.site)», we are investigating young people who experience changes in thinking and perception to varying degrees or frequently in a longitudinal approach using, among other things, a portable high-resolution sleep EEG.
Our results will contribute to a better understanding of the interplay between changes in sleep and changes in thinking and perception during wakefulness. The project will complement previous research examining the extent to which sleep spindles could support early diagnosis as a biomarker. In addition, innovative therapies can be further developed around the clock and adapted for young people.
