Abstract/Summary

Heart rate variability (HRV) has gained popularity in psychological research as it has been proposed to be correlated with emotion regulation capabilities, psychopathology, and psychological well-being. Previous HRV research provides evidence to suggest that individuals with higher HRV (at rest and during emotional regulation tasks) may have better mental health and well-being outcomes, but the underlying mechanisms from adolescence to adulthood are still unclear. This thesis explores the relationship between HRV, functional connectivity in the brain, and emotional experience in daily life. In addition, the existing research is limited to western countries, therefore, it is difficult to infer whether the findings from HRV in western populations might apply to under-researched populations (i.e. non-western populations). To improve its generalisability and validity as a tool to index cardiac autonomic regulation, HRV research should include diverse samples (i.e. western and non-western populations). In an attempt to examine brain activity and psychological mechanisms of HRV in daily life, three studies were conducted. The first study of this thesis assessed the relationship between HRV during emotion regulation tasks and amygdala-medial prefrontal cortex (mPFC) functional connectivity during rest across young and older adults. The results showed that higher HRV during emotion regulation tasks was associated with stronger amygdala-mPFC connectivity during rest across young and older adults. The second study examined the relationship between HRV during rest and amygdala-mPFC connectivity during rest in another sample of young and older adults. Unlike the first study, we found no significant associations. However, when we further investigated the relationship between HRV during rest and daily emotional experience, the results showed a significant relationship between them. The third study followed the second study and explored the relationship between HRV during rest, emotional experience, and perceived stress levels in adolescents from a developing country. The results showed a significant relationship between resting-state HRV and perceived stress. Taken together, the findings from these studies extend prior studies for the links between HRV, brain functional connectivity, perceived stress, and daily emotional experience. As far as we are aware, this thesis also provides the first evidence that HRV can be used to index stress levels of individuals even in a previously under-investigated sample, adolescents in developing countries.