Internal brain dynamics assessment by heart rate variability

Introduction: Salience network (SN) has been proposed to play a role in the switchings between default mode network (DMN) and central executive network (CEN) induced by salient stimuli or in stressful conditions (V Menon et al, ‎2010). Based on the neurovisceral integral model of Thayer and colleagues, heart rate variability (HRV) can serve as an index of the brain network interactions (Thayer et al, 2000; Smith et al, 2017 ). Methods: The present study aimed to examine the association of HRV with brain network interactions in a sample of 38 healthy male subjects. Resting state fMRI data were acquired in two sessions, the baseline and right after the scan stress task. To test our hypothesis, dynamic functional connectivity between SN-CEN, SN-DMN, DMN-CEN, and their correlation to HRV were calculated separately using a sliding window approach. HRV is calculated in term of RMSSD (root mean square of succeeding interbeat intervals). The mixed effect analysis was conducted to analyze the interaction of brain network pairs, stress, and HRV. Results: A significant interaction effect of session and network pair was found on correlation of HRV and functional connectivity between network pairs (p = 0.005). Follow-up tests showed that HRV correlated more strongly with SN-DMN functional connectivity than with SN-CEN (p = 0.09, bonferroni adjusted) and with DMN-CEN (p = 0.049, bonferroni adjusted) in the baseline resting condition. In addition correlation between HRV and SN-DMN was significantly decreased after scan stress task (p = 0.006, bonferroni adjusted). No significant effect of reactivity of saliva cortisol and alpha amylase levels to scan stress task, subjective ratings of stress after task and age was detected after introducing as additional regressors. Conclusions: These results point out to possible contribution of HRV to dynamic interactions between brain networks