Fig. 4: MEC isolated theta waves are positively correlated with increase in the activities of RE neurons projecting to the MEC.

A Diagram for simultaneously fiber photometry recording of RE neurons projecting to MEC as well as LFP recordings in the MEC. B Representative image showing the expression of jGCamp7b (green) and the optical fiber (dotted yellow pane) implanted in the RE (left) and the electrode implanted in the MEC (right, yellow arrowhead), and related enlarged view. C Representative raw EEG-EMG traces, color-coded hypnogram, and Ca²⁺ signals from a RE-MEC^jGCamp7b mouse. D Two examples showing synchronous recordings of Ca²⁺ activity of RE neurons projecting to MEC (top) and LFP in the MEC (bottom) during NREM sleep. Between two dotted white lines is theta frequency band (4–12 Hz). E Heatmaps illustrating synchronous change of Ca²⁺ activity of RE neurons projecting to MEC (top) and increment of theta/(delta + theta) ratio (ΔTheta ratio, bottom) around Ca²⁺ peak (0 s) during NREM sleep (n = 8 mice). F Average value of synchronous change of Ca²⁺ activity (top) and ΔTheta ratio (bottom) from 8 mice displayed as (E). Data are presented as mean (red line) ± s.e.m. (shaded area). G Statistic analysis of ΔTheta ratio before and during the period of Ca²⁺ peak (two-tailed paired t test, n = 8 mice, t₇ = −6.672, P = 0.000285). ***P < 0.001. Data are presented as mean ± s.e.m. Source data are provided as a Source Data file.