Figure 5. Phase transitions in the strength of two different forms of cardio-respiratory coupling across sleep stages.

(a) RSA and (b) CRPS exhibit very different stratification patterns across sleep stages, indicating (i) that each form of cardio-respiratory coupling undergoes a complex re-organization with sleep-stage transitions; and (ii) that RSA and CRPS are two independent forms of coupling, the streghten of which change differently during different sleep stages. Columns in each panel represent the group average of all subjects; error bars correspond to the standard error. CRPS is estimated as the percent of data segments in the entire recording for a given sleep stage where heart rate and respiratory rate are phase-synchronized.