Sleepwalking is a pathology that has long fascinated philosophers, scientists, and artists, yet remains poorly understood and overlooked by researchers. Historically considered a “sacred” illness and perceived as a divine phenomenon, sleepwalking has lost much of its mystical aura over time. However, the perception of sleepwalkers as automatons, largely unaware of their nocturnal episodes, persists in both public and clinical spheres. This thesis seeks to explore how “unconscious” sleepwalkers truly are during episodes and what their nocturnal behaviors reveal about cognition during sleep.Disorders of Arousal (DoA), which include sleepwalking, night terrors, and confusional arousals, manifest as complex behaviors emerging from slow-wave sleep. Current diagnostic criteria suggest an altered state of consciousness during DoAs, characterized by absent or inappropriate reactivity to external stimuli, lack of dreams or very short dreams, and partial or total amnesia of episodes. However, few studies have thoroughly examined patients' state of consciousness during these episodes. This thesis aims to refine our cognitive and phenomenological understanding of DoAs, focusing on the mental content experienced by patients, their perception and reaction to the outside world, and the potential link between the two. Additionally, it explores whether auditory cues presented during slow-wave sleep can trigger behavioral reactivation of motor learning.In the first study, we used questionnaires, auditory stimulation during sleep monitored in the lab, and video recordings of episodes at patients' homes to evaluate the relevance of current diagnostic criteria for DoA. We assessed patients' interaction with their environment, their mental content during episodes, and their ability to recall episodes immediately upon waking or later. Results indicate a variety of states of consciousness during DoA episodes. Notably, 84% of patients reported dreams during episodes, ranging from short, frightening scenes to complex narratives. Furthermore, 81% of patients reported conversing with partners during episodes, corroborated by 37 video recordings showing such interactions. These verbal interactions and perceptions were often linked to dream content. A majority of patients recalled episodes to some extent, with 52% able to recall aspects when confronted with contextual cues in daily life, suggesting partial memory encoding. These findings highlight the complexity of consciousness during DoA episodes and suggest the need to reassess current diagnostic criteria.The second study aimed to access real-time motor learning consolidation processes and associated mental content during sleep. The hypothesis was that behaviors observed during parasomnia episodes represent externalized dreams, providing a unique opportunity to explore cognitive processes. Using the Targeted Memory Reactivation (TMR) paradigm, sound cues associated with motor learning during wakefulness were replayed during sleep to trigger behavioral and mental reactivations. Preliminary results from 11 patients showed no behavioral reactivation during episodes triggered by sound cues, but some incorporation of sounds into dreams was observed. Potential reactivations, though rare, might occur later or in the following days, suggesting long-term integration of learning into dreams. Additionally, motor task performance post-sleep did not differ between DoA patients and healthy controls, indicating that DoA does not negatively impact sleep-dependent memory consolidation. These results require confirmation with a larger sample.In conclusion, this thesis reveals that the state of consciousness during DoA episodes is richer and more variable than current criteria suggest. Given that patients can interact with others during episodes, they provide a promising model for exploring cognitive and mental processes during slow-wave sleep.