Optimizing automated phase-targeted auditory stimulation protocols for procedural memory consolidation during sleep...

Up-phase-targeted auditory stimulation (up-PTAS) during slow-wave sleep has become a valuable tool for modulating slow oscillations and slow oscillation-spindle-coupling in favor of overnight memory retention. Developing effective, automated protocols for translation into more naturalistic and clinical settings is an ongoing challenge, especially because current PTAS protocols and their behavioral effects vary greatly between studies. Our study contributes to ongoing efforts in characterizing parameter choices in PTAS and compares two up-PTAS protocols with systematic variations of the interstimulus intervals (ISIs) and their effect on the consolidation of a finger-tapping sequence using a mobile PTAS device and an app-based behavioral task in a home setting. Participants tolerated both protocols well and showed high adherence to the study procedures. Electrophysiological stimulus responses and learning trajectories in the finger-tapping task replicated lab-based findings. We extend studies suggesting a nonlinear relationship between stimulus number and PTAS effects by showing that applying fewer stimuli with longer ISIs enhances overnight consolidation of a finger-tapping sequence more effectively than applying more stimuli with shorter ISIs. Exploratory electrophysiological analyses revealed that the behavioral response was positively correlated with the number of stimuli with auditory evoked K-complexes relative to the number of stimuli without K-complexes. PTAS stimuli with longer ISIs (>1.25) were associated with a higher likelihood of K-complex responses and increased spindle power. Our findings demonstrate the feasibility of mobile, at-home PTAS combined with app-delivered behavioral tasks in healthy participants and can inform the development of more effective memory enhancement protocols.