Effects of daily heart rate variability biofeedback practice on the amygdala's structural covariance network

The neurovisceral integration model posits that the reciprocal interaction between the amygdala and prefrontal cortex (PFC) influences heart rate variability (HRV) and emotion modulation. Emerging evidence also suggests that HRV influences brain regions involved in emotion regulation. Building on previous functional magnetic resonance (fMRI) studies, the present study employed structural covariance analysis to examine the effects of HRV biofeedback intervention on the structural covariance between the amygdala and cortical regions. Investigating the covariation between the amygdala and cortical regions during a biofeedback intervention can provide insight into how HRV regulatory attempts influence neural structures involved in HRV and emotion regulation. Baseline and post-intervention MRI scans were collected from 151 participants (100 younger and 51 older adults) who completed 5 weeks of daily biofeedback sessions to either increase (Osc + condition) or decrease (Osc- condition) HRV. Across both age groups, the two intervention conditions were associated with opposing patterns of structural covariance between the right amygdala and the left medial prefrontal cortex (mPFC). In the Osc + condition, volume changes in the left amygdala showed an inverse association with volume changes in the right orbitofrontal cortex (OFC), while no association was observed in the Osc- condition. These findings are consistent with the neurovisceral integration model perspective that the PFC exerts inhibitory influence over subcortical structures and that HRV influences brain regions involved in emotion regulation.