Sleep Spindle–Slow Oscillation Coupling in Typical and Neurodiverse Development

Precise temporal coordination, or coupling, of two neural oscillations during non-REM sleep – slow oscillations and sleep spindles – is recognized as a fundamental characteristic of healthy sleep and cortico-thalamic circuitry. Coupling is tightly linked to memory consolidation, further underscoring the need to understand its development. In this preregistered cross-sectional study using existing polysomnographic datasets, we tested associations between coupling metrics and age in typically developing (N = 84) and neurodiverse (N = 40) children and adolescents (~7.5-14.5 years old), and linked coupling precision to slow oscillation and spindle characteristics. The analyses substantially advance current understanding of the coupling mechanism during sleep: 1) We report an increase with age in coupling density in typically developing children that was mostly driven by an increase in overall spindle density. 2) Using a statistical model of coupling consistency – a key metric of coupling – we showed that slow-oscillation amplitude and spindle density were its strongest predictors in typically developing children. 3) We found no group differences in any coupling metric between neurodiverse (with dyslexia or autism) and typically developing children when collapsing across age. Furthermore, only coupling consistency, but not prevalence, was significantly associated with age in the neurodiverse sample. and we were not able to fit a model for coupling consistency for neurodiverse data. The results show that it is important to examine how age relates to the prevalence of coupling events, not only to coupling precision, and that developmental trajectories of coupling may be important markers of brain health - pending confirmation in longitudinal work.