0267 Infraslow Oscillations During Non-Rapid Eye Movement Sleep Across the Life Course

Abstract Introduction Sleep spindles, hallmark of stage 2 (N2) non-rapid eye movement (NREM) sleep, fluctuate in an infraslow oscillation (ISO; ~0.02Hz) regulated by the noradrenergic system and locus coeruleus. The temporal dynamics of ISOs, their frequency-domain extent, and how they evolve with age remain largely unexplored. Here, we examined how ISOs across a broad frequency range (0.5-30Hz) change across the life course, how different frequency bands synchronize in the infraslow domain, and how ISOs couple with phasic NREM sleep events to better understand their functional role in sleep neurophysiology. Methods We analyzed polysomnographic data (N=13,529, age: 3-85 years) from the National Sleep Research Resource. ISO power and peak frequency were derived from the frequency decomposition of the N2 spectrogram (0.5-30 Hz) and averaged across seven canonical bands: slow (0.5–1Hz), delta (1–4Hz), theta (4–7Hz), alpha (7–10Hz), slow sigma (10–12Hz), fast sigma (12–15Hz), and beta (15–30Hz). ISOs were characterized in the time domain after filtering the signals resulted from the first frequency decomposition in the 0.01-0.03Hz. Results All frequency bands exhibited infraslow modulation. ISO power and peak frequency showed significant age-related changes, with fast sigma power displaying an inverted U-shaped trajectory and the largest effect size (η²=.03, p<.001). ISO power was highly reliable within individuals (rs>.45 and ps<.001). Across bands, ISOs showed a characteristic non-sinusoidal waveform in which the negative half-wave was shorter and lower in amplitude than the positive (ps<.001). Time-domain analyses revealed cross-band synchronization: in childhood, slow sigma was followed by fast sigma; whereas in adulthood, fast sigma became the leading rhythm. Slow, fast spindles and slow waves occurred preferentially during the positive half-wave of the fast sigma ISO, an effect more pronounced in adulthood. Conclusion ISOs were evident across all frequency bands and showed robust, age-dependent changes in power, peak frequency and waveform independent of average band power. Distinct cross-band synchronization suggests that infraslow modulation during NREM sleep reflects coordinated activity within widespread cortical-subcortical circuits. These findings define normative trajectories of ISO dynamics and their coordination across the life span. Support (if any) DM was supported by the AASM Strategic Research Grant and the Mass General Neuroscience Transformative Scholar Award.