Chaotic fluctuations in heart rate variability associated with interaction of large-scale brain networks: experiments and hypotheses

Heart rate variability (HRV) caused by the involvement of the autonomic nervous system is analysed for evaluation of autonomic nervous activity using methods standardized by time-domain and frequency-domain analysis. Conventional HRV analysis captures only a limited aspect of HRV, and in recent years new attention has been focused on analysis from the perspective of chaos/complexity. To clarify the characteristics of these analyses, we comprehensively compared the time-domain, frequency- domain, and chaos/complexity indices in RRIs measured under physical and mental load. In contrast to conventional indices, the indices of chaos/complexity increased significantly in mental load. From this result, we proposed the model, which is consistent with previous studies, explains that chaotic/complexity of HRV is an important quantity that deeply related to brain activity.