BACKGROUND: Cortical correlates to heart rate variability (HRV) are assumed to involve interconnectivity between single brain areas and large-scale brain networks (LSN) in the extended...Show moreBACKGROUND: Cortical correlates to heart rate variability (HRV) are assumed to involve interconnectivity between single brain areas and large-scale brain networks (LSN) in the extended neurovascular integration model (NVI). Among those are the CEN and the DMN from the triple network model (TNM) and the anterior insula (AI) and the dorsal anterior cingulate cortex (DACC). This study aimed to test if AI and DACC are involved as the SN in FC patterns that correlate to HRV. Second, it was tested if LSN show FC patterns in accordance with the TNM during experimental tasks. METHODS: 27 female participants (18- 35 years) took part in this cross-sectional fMRI study. Experimentally induced FC patterns of the three LSN with HRV as a covariate were used for the statistical model. RESULTS: As hypothesised, the CEN showed significantly more intrinsic FC during the WMT which was associated with HRV. Further, there was an association between HRV and the FC between the CEN and AI/ACC, respectively. Against the hypothesis, an involvement of the full SN could not be confirmed. The results concerning the DMN disconfirm the hypothesis of an increased FC during the rumination condition. Lastly, a trend was visible for lower HRV during the WMT compared to the rumination condition, but this difference did not reach the significance level. CONCLUSION: The present results confirm the AI and ACC as autonomous brain regions involved in FC patterns associated with HRV. This confirmation of the NVI opposes the unexpectedly high FC pattern of the DMN during the WMT, which points to explanatory gaps in the external validity of the model and the role of LSN vs. single brain regions as associates of HRV.Show less
Research master thesis | Psychology (research) (MSc)
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Introduction: The default mode network (DMN) is a large intrinsic network in the brain, which seems to be affected in depressed patients. Also, aberrant heart rate variability (HRV) is often found...Show moreIntroduction: The default mode network (DMN) is a large intrinsic network in the brain, which seems to be affected in depressed patients. Also, aberrant heart rate variability (HRV) is often found in this population. Ketamine is thought to be a fast-acting antidepressant and has shown to have an effect on HRV and intrinsic brain connectivity. In this study, the effect of HRV on resting-state functional connectivity of the DMN and brain activity of areas within the DMN that were significantly correlated with HRV was examined. Also, it was investigated whether ketamine moderated this relationship. Method: Twelve healthy men received an intravenous ketamine or placebo infusion on two occasions. Resting-state functional connectivity and HRV were measured before, during, and after infusion. Dual-regression was used to obtain DMN connectivity scores, while a whole brain analysis was done to determine which brain areas were correlated with HRV. Raw digitized electrocardiogram (EKG), obtained with a pulse oximeter, was analyzed in order to extract HRV data. Multilevel analysis was used to determine the effect of HRV and ketamine on resting-state functional connectivity in the DMN and brain activity in the subgenual anterior cingulate cortex (sgACC), right dorsolateral prefrontal cortex (dlPFC), and the left postcentral gyrus. Results: DMN connectivity strength was negatively related to HRV, but positively related to activity of the right dlPFC and the left postcentral gyrus for the placebo condition. Ketamine was associated with a more profound effect of HRV on DMN connectivity and brain activity within the postcentral gyrus. Discussion: The present results complement recent studies that show that HRV is associated with connectivity strength in the DMN. Implications for the relevance of using ketamine in depressed patients are discussed. Initial increases of DMN connectivity are followed by a decrease in the DMN, which may be beneficial for depressed patients who generally show hyperconnectivity within the DMN. Results thus imply that ketamine has a moderating role in this.Show less
