Fig. 2: Cumulative disruption, hemispheric asymmetry and ordering irregularity at sleep onset.
From: Disordered descent into sleep: microstructural divergence across arousal-linked conditions
A Z-normalised cumulative timing deviation (Z-AUC) across H4–H10 (mean ± SEM) for each diagnostic group and controls. Positive values indicate prolonged onset relative to controls; negative values indicate compressed onset. B Hemispheric Laterality Index (LI) distributions across H4–H10, where LI is the difference between right- and left-hemisphere dwell time divided by their sum; positive values indicate right-hemispheric predominance. C Cumulative Ordering Index (COI) summarising the fraction of adjacent canonical Hori substages whose empirical first-arrival order is inverted, plotted against inversion magnitude in seconds for each subject. Coloured ellipses show 68% covariance contours; crosses mark group means. D Overlaid ellipses from panel c provide a compact view of ordering frequency and size across disorders. Together, Z-AUC, LI and COI capture onset tempo, hemispheric balance and sequence coherence, highlighting compressed, irregular onset in narcolepsy and prolonged, near-canonical onset in fibromyalgia, with iRBD and NREM parasomnia closer to controls. Colours: narcolepsy (gold), fibromyalgia (red-orange), iRBD (blue), NREM parasomnia (magenta), controls (grey). Error bars represent standard error of the mean. Non-parametric tests with two-sided p values are used for group comparisons, with multiplicity controlled for the prespecified primary endpoints. COI Cumulative Ordering Index, Z AUC Z normalised area under the H4–H10 curve, LI Laterality Index, iRBD idiopathic REM sleep behaviour disorder.
