Fig. 6
From: Bidirectional prefrontal-hippocampal dynamics organize information transfer during sleep in humans
Precise SO-spindle coupling phase modulates MTL-PFC connectivity. a Single subject example of EEG-MTL connectivity calculated separately for coupled spindles (black), uncoupled/isolated spindles (purple), and random event-free intervals (gray). Event numbers were equated by a bootstrapping procedure. Note the distinct peak in the spindle band. b We re-aligned power spectra to the individual spindle peak (14.5 ± 2.6 Hz; mean ± SD) and mean-normalized the aligned spectra to minimize inter-subject variability. c We then extracted the normalized EEG-MTL iPLV peak values for all events. A repeated measures ANOVA revealed a significant main effect (F1.49,25.27 = 7.93, p = 0.0043, η2 = 0.21; p-values from post-hoc pair-wise comparisons are depicted). We found significantly more inter-areal connectivity for coupled than for uncoupled spindles or random event-free intervals. d Directionality analysis during spindle events revealed a significant influence from prefrontal EEG spindles to the MTL (dark gray) as compared to a surrogate distribution (light gray). e Two single subject examples of event-locked spindle connectivity as a function of the precise coupling phase (mean ± SEM). Upper: the spindle band exhibits a strong peak in the spectrum and also peaks in the standard deviation spectrum (inset in red), thus, indicating that the spindle band exhibits the largest variance. f Spindle-band connectivity binned as a function of the precise coupling phase revealed strong non-uniform distributions. We highlighted the worst (lowest synchrony; red) and best (highest synchrony; blue) phase. g Anti-phasic relationship between best and worst connectivity phase (EEG-MTL: V-test against ±π: v = 7.33, p = 0.0073, mvl = 0.49). h Realigned (to the best phase) grand average spindle (12–16 Hz) iPLV histogram reveals a non-uniform relationship (mean ± SEM) between SO-Spindle coupling and EEG-MTL phase locking. Note we excluded the central aligned phase bin from subsequent testing (RM-ANOVA: F5.23,88.83 = 3.13, p = 0.011, η2 = 0.15). All error bars indicate the mean ± SEM
