INVESTIGATING THE EFFECTS OF CLOSED-LOOP AUDITORY STIMULATION DURING SLEEP IN OLDER ADULTS

Sleep plays a critical role in memory consolidation, yet this process becomes less efficient with ageing. Closed-loop auditory stimulation has emerged as a non-invasive approach to enhance oscillatory activity during sleep, but achieving precise phase targeting in older adults remains challenging. This study investigates the feasibility and physiological effects of closed-loop auditory stimulation on slow oscillations in older adults. Participants aged 40 years and over complete two overnight sleep laboratory visits (stimulation and sham), separated by at least one week. During each session, polysomnography[AS1] is used to detect slow oscillations in real time using an automated algorithm, enabling auditory stimuli to be delivered during the up-state of slow oscillations in slow-wave sleep.
Preliminary analyses demonstrate precise phase targeting by the closed-loop system. Across 12 overnight sessions (10,391 total stimulations; mean 866 ± 718 per night), stimuli were consistently delivered during the intended up-state of the slow oscillation. Phase-locking analysis revealed a pooled circular mean of 320.2° (approximately 40° before the positive peak), high phase concentration (R = 0.81), and a significantly non-uniform phase distribution (Rayleigh p < 0.001), indicating stable and accurate stimulation timing across sessions.
Data collection is ongoing, with final analyses scheduled prior to the conference. We hypothesise that closed-loop auditory stimulation during slow-wave sleep will increase slow oscillation amplitude and enhance slow oscillation-spindle coupling. Planned analyses will also examine whether these neurophysiological effects lead to improved overnight memory retention, informing the translational potential of auditory stimulation as a non-invasive neuromodulation approach for older adults.