# Optimizing automated phase-targeted auditory stimulation protocols for procedural memory consolidation during sleep in a home setting

## TL;DR

This study shows that using sound during sleep to improve memory works better at home when sounds are spaced farther apart.

## Contribution

The study introduces a home-based PTAS system and shows that longer intervals between sounds enhance memory consolidation.

## Key findings

- Fewer, spaced auditory stimuli during sleep improve finger-tapping memory consolidation more effectively.
- Longer interstimulus intervals increase K-complex responses and spindle power.
- Home-based PTAS with mobile devices is feasible and replicates lab-based results.

## Abstract

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.

Statement of Significance Phase-targeted auditory stimulation (PTAS) holds great promise for non-invasively enhancing essential functions of slow-wave sleep. However, current protocols have produced variable results and are often confined to laboratory settings. Our study demonstrates the feasibility of an at-home application of automated PTAS and provides experimental evidence that prolonging interstimulus intervals may positively affect overnight procedural memory consolidation via K-complexes and sleep spindles. Together, our findings lay a foundation for a broader application of PTAS in longitudinal clinical studies to improve patient care and recovery outcomes.