Closed‐Loop Targeted Memory Reactivation During Sleep Spindles Enhances Motor Memory Consolidation

ABSTRACT

Sleep spindles are thought to facilitate motor memory consolidation by reactivating recently acquired memory traces during non‐rapid eye movement (NREM) sleep, yet most human evidence is correlational. Using a closed‐loop targeted memory reactivation (CL‐TMR) protocol, this study tested whether auditory cueing time‐locked to spindles enhances the consolidation of a newly acquired motor sequence. Twenty‐six young adults practiced two eight‐element, explicitly known, sequences of finger movements, each paired with a distinct auditory cue. During subsequent NREM Stage 2 and 3 nighttime sleep, a portable deep‐learning‐based EEG device (Portiloop) detected spindles online and selectively replayed the cue associated with one sequence (TMR condition), while the other served as a within‐subject non‐reactivated control (non‐TMR) condition. Behavioural performance was assessed before and after sleep. Greater overnight improvements in performance were observed for the reactivated as compared to the non‐reactivated condition, hence demonstrating enhanced consolidation following spindle‐locked CL‐TMR. The magnitude of this TMR benefit was positively correlated with the percentage of stimulations delivered during true spindles. Furthermore, a higher percentage of stimulations occurring during spindle trains (i.e., two or more spindles separated by < 6 s) was associated with larger TMR‐induced gains, whereas a higher percentage during isolated spindles (> 6 s apart) was associated with reduced gains. These findings provide further evidence that spindle‐timed reactivation supports motor memory consolidation in humans and suggest that spindle trains may represent a favourable physiological window for closed‐loop interventions.