Sleep-dependent memory consolidation relies on the temporal coordination of sleep oscillations, including cortical slow oscillations (SOs) and thalamic spindles, during non-rapid-eye-movement (NREM) sleep. Reduced spindle activity and correlated impairments in sleep-dependent memory are reported in healthy aging and neurodegenerative  disorders. Yet treatments that improve memory impairments are lacking.  Auditory stimulation, time-locked to the SO upstate, is a promising potential treatment.  In healthy adults it evokes SOs and spindles, and improves declarative memory. We investigated whether auditory stimulation can evoke coupled SO-spindle events and improve procedural memory as well.

Auditory stimulation evoked more coupled SO-spindle events than detection only in a fronto-central cluster of electrodes (clustered t-stat=49.6, p<.05). While there was no significant effect of condition on memory, the higher the stimulation rate (#/min), the greater the memory improvement in the stimulation  (r=.52, p<.05), but not detection (r=.32, p=.16) condition, although these relations did not differ significantly. Additionally, coupled SO-spindle density (#/min) in a centro-parietal cluster significantly correlated with memory improvement  (r²=.29, p=.05).

Auditory stimulation evokes coordinated spindle-SO events that mediate memory consolidation. The higher the rate of stimulation, the greater sleep-dependent memory consolidation, suggesting a dose-dependent effect. This motivates the investigation of auditory stimulation as a non-invasive and potentially scalable treatment for sleep-dependent memory deficits.