Random auditory stimulation disturbs traveling slow waves and declarative memory

Sleep plays a crucial role in memory consolidation, and various methods have attempted to enhance this process by using auditory stimulation to modulate slow waves or trigger memory reactivation. However, the broader impact of auditory stimulation on sleep physiology and memory retention is not fully understood. Here, we apply random or sham auditory stimulation during an afternoon nap in a within-subject design to investigate its effects on declarative and procedural memory consolidation and electrical brain activity during sleep. Stimulation led to a specific reduction in slow-wave sleep, a decreased slow-wave count, and impaired declarative recall that correlated with the diminished sleep depth. Furthermore, we observed altered slow-wave traveling dynamics, with stimulation resulting in shorter traveling trajectories with less reach and reduced spatial spread, particularly impacting frontal regions. Disruptions in these features correlated with memory deficits. Our findings highlight the role of dynamic slow-wave properties in declarative memory consolidation and reveal some methodological limitations for using auditory cues during sleep, given their potential to disrupt complex processing patterns.