Fig. 5: Dendritic Ca²⁺ spikes increase during REM sleep.

a Two-photon Ca²⁺ imaging of apical tuft dendrites of layer 5 pyramidal neurons in head-restrained mice during quiet awake, NREM sleep, and REM sleep. b, c Ca²⁺ imaging of apical tuft dendrites under various states in V1 (b) and FrA (c). Scale bar, 10 µm. Ca²⁺ fluorescence traces of three dendrites over 30 s are shown. d, g The number of dendritic Ca²⁺ spikes during REM sleep was significantly higher than that in other brain states in both V1 (d) (n = 4 mice, P < 0.0001 and = 0.0004 for REM sleep vs. quiet awake and NREM sleep, respectively) and FrA (g) (n = 5 mice, P = 0.0019 and = 0.0117 for REM sleep vs. quiet awake and NREM sleep, respectively) (Wilcoxon–Mann–Whitney test, two-sided). e, h The integrated activity of dendritic Ca²⁺ spikes during REM sleep was significantly higher than those during NREM sleep and quiet awake state in both V1 (e) (n = 4 mice, P < 0.0001 and = 0.0003 for REM sleep vs. quiet awake and NREM sleep, respectively) and FrA (h) (n = 5 mice, P < 0.0001 for REM sleep vs. quiet awake and NREM sleep, respectively) (Wilcoxon–Mann–Whitney test, two-sided). f, i The duration of dendritic Ca²⁺ spikes during REM sleep was significantly longer than those during other brain states in both V1 (f) (n = 4 mice, P = 0.0002 and = 0.0163 for REM sleep vs. quiet awake and NREM sleep, respectively) and FrA (i) (n = 5 mice, P = 0.0012 and = 0.0394 for REM sleep vs. quiet awake and NREM sleep, respectively) (Wilcoxon–Mann–Whitney test, two-sided). *P < 0.05, **P < 0.01, ***P < 0.001. Data are presented as mean ± s.e.m. In (d–i), each circle represents one active dendrite, n = 22, 9, and 78 dendrites for quiet awake, NREM sleep and REM sleep, respectively in V1; n = 18, 7, and 118 dendrites for quiet awake, NREM sleep and REM sleep, respectively in FrA. Source data for (d–i) are provided as a Source Data file.