Topographical Patterns of Slow Wave Activity in Sleep Talking: An Exploratory Polysomnographic Investigation

Sleep talking (ST) is a parasomnia characterized by the utterance of unaware linguistic activations during sleep. Electrophysiological evidence is scarce, and it remains unclear whether local electroencephalographic (EEG) alterations characterize the sleep of STs outside of parasomnia episodes. Findings from NREM parasomnias suggest that local slow-wave activity (SWA) abnormalities may characterize a full night's sleep beyond behavioural manifestations. Accordingly, this study investigates SWA topography and the spatial distribution of the single SWA bins across sleep stages in a group of 12 young STs compared to 10 healthy controls (HCs) matched for sex and age, who underwent overnight laboratory polysomnographic recordings. The relationship between SWA pattern and parasomnia frequency was explored, and the overnight decline in SWA was examined to assess the potential impact of homeostatic processes. Our findings point to a peculiar SWA pattern characterized by a substantially stable central increase across sleep stages and a frontopolar decrease primarily in N2 sleep, suggesting a local and frequency-specific (≥ 1 Hz) SWA regulation in STs that may interact with homeostatic processes. These results provide new insights into the sleep electrophysiology of STs and shed light on trait-like regional alterations in SWA that may facilitate parasomnia events. Our findings align with the concept of local sleep, which posits that distinct cortical regions may simultaneously exhibit diverse functional states. In this view, different parasomnias may be characterized by specific SWA topographical patterns reflecting the peculiar behaviours enacted during sleep.