Stimuli caused by our own voluntary actions receive a special treatment in the brain. In auditory processing, the N1 and/or P2 components of the auditory event-related brain potential (ERP) to self-initiated sounds are attenuated compared to passive sound exposure, which has been interpreted as an indicator of a predictive internal forward mechanism. Such a predictive mechanism enables differentiating the sensory consequences of one´s own actions from other sensory input and allows the mind to attribute actions to agents and particularly to the self, usually called the “sense of agency”. However, the notion that N1 and/or P2 attenuation effects to self-initiated sounds reflect internal forward model predictions is still controversial. Furthermore, little is known about the relationship between N1 and/or P2 attenuation effects and the sense of agency. Thus, the aim of the present thesis was to further investigate the nature of the N1 and/or P2 attenuation effect to self-initiated sounds and to examine its specific relationship to the sense of agency. The present thesis provides evidence that N1 and/or P2 attenuation effects to self-initiated sounds are mainly determined by movement intention and predictive internal motor signals involved in movement planning and rules out non-predictive explanations of these effects. Importantly, it is shown that sensory attenuation effects in audition are directly related to the feeling of agency, but occur independent of agency judgments. Taken together, the present thesis supports the assumptions of internal forward model theories.

In dieser Studie untersuchten wir den Mechanismus und die neuronalen Strukturen, die an der auditorischen Filterung bedeutungsvoller Reize während des Schlafs beteiligt sind. Zunächst entwickelten wir ein Verhaltensparadigma, bei dem Geräusche in einer bedeutungsabhängigen Weise Veränderungen in schlafassoziierten Oszillationen hervorrufen. Interessanterweise traten diese Störungen bereits bei niedrigen Schallintensitäten während des NREM- und REM-Schlafs auf, was die starke Einflussnahme bedeutungsvoller Reize auf die Schlafdynamik betont. Darüber hinaus unterstrich unsere Analyse von Verallgemeinerungsseffekten unter Verwendung verschiedener neutraler Klangreize die breite Wirkung bedeutungsvoller Klänge auf das EEG, unabhängig von der Unterscheidbarkeit der Geräusche. Wir erweiterten unserer Verhaltensparadigma auf kopffixierte Tiere und konnten NREM- und REM-Schlafphasen nach einer längeren Habituation nachweisen. Bemerkenswerterweise waren unsere Befunde für kopffixierte im Vergleich zu sich frei bewegenden Tieren sehr ähnlich, da das konditionierte Geräusch im Vergleich zu neutralen Reizen einen erhöhten Einfluss auf schlafassoziierte Oszillationen hatte. Schließlich untersuchten wir den neuronalen Zusammenhang der auditiven Verarbeitung während des Wachzustands und des Schlafs, wobei wir uns auf den Colliculus Inferior (CI) konzentrierten. Unsere Analysen enthüllten unterschiedliche neuronale Reaktionen auf bedeutungsvolle und neutrale Reize, wobei der bedeutungsvolle Reiz während des Wachzustands, aber nicht während des NREM-Schlafs, höhere Feuerraten auslöste, was auf eine zustandsabhängige neuronale Verarbeitung hinweist. Darüber hinaus zeigten unsere Untersuchungen eine verstärkte zeitliche Musterbildung als Reaktion auf den bedeutungsvollen Reiz während des NREM-Schlafs, was auf eine Rolle des CI bei der Kodierung bedeutungsvoller auditorischer Reize während des Schlafs hindeutet. Insgesamt liefert unsere Studie überzeugende Belege dafür, dass die Bedeutung eines Geräuschs signifikanten Einfluss auf schlafassoziierte Oszillationen sowie zeitliche Muster der neuronalen Aktivität im IC hat. / In this study, we delved into the mechanism and neural structures involved in the auditory gating of meaningful stimuli during sleep. First, we developed a behavioural paradigm in which sounds elicit changes in sleep-associated oscillations in a meaning-dependent manner. Interestingly, these disruptions occurred even at relatively low sound intensities during NREM and REM sleep, highlighting the potent influence of meaningful stimuli on sleep dynamics. Additionally, our exploration of generalization effects using various neutral sound stimuli underlined the broad influence of meaningful sounds on NREM EEG patterns, independent of sound discriminability. We extended our investigation to head-fixed animals, confirming their ability to achieve NREM and REM sleep phases following a prolonged habituation period. Notably, our findings were very similar for head-fixed compared to freely moving animals since the conditioned sound had increased influence on sleep-associated oscillations, compared to neutral stimuli. Finally, we studied the neural correlates of auditory processing during wakefulness and sleep, focusing on the inferior colliculus (IC). Our analyses revealed differential neuronal responses to meaningful and neutral stimuli, with the conditioned sound eliciting higher firing rates during wakefulness but not during NREM sleep, indicating state-dependent neural processing. Furthermore, our investigations unveiled enhanced temporal patterning in response to the conditioned sound during NREM sleep, suggesting a role of the IC in encoding meaningful auditory stimuli during sleep. Overall, our study provides compelling evidence that the meaning of a sound significantly influences sleep-associated oscillations as well as temporal patterning of neural activity in the IC.

Stimuli caused by our own voluntary actions receive a special treatment in the brain. In auditory processing, the N1 and/or P2 components of the auditory event-related brain potential (ERP) to self-initiated sounds are attenuated compared to passive sound exposure, which has been interpreted as an indicator of a predictive internal forward mechanism. Such a predictive mechanism enables differentiating the sensory consequences of one´s own actions from other sensory input and allows the mind to attribute actions to agents and particularly to the self, usually called the “sense of agency”. However, the notion that N1 and/or P2 attenuation effects to self-initiated sounds reflect internal forward model predictions is still controversial. Furthermore, little is known about the relationship between N1 and/or P2 attenuation effects and the sense of agency. Thus, the aim of the present thesis was to further investigate the nature of the N1 and/or P2 attenuation effect to self-initiated sounds and to examine its specific relationship to the sense of agency. The present thesis provides evidence that N1 and/or P2 attenuation effects to self-initiated sounds are mainly determined by movement intention and predictive internal motor signals involved in movement planning and rules out non-predictive explanations of these effects. Importantly, it is shown that sensory attenuation effects in audition are directly related to the feeling of agency, but occur independent of agency judgments. Taken together, the present thesis supports the assumptions of internal forward model theories.