Spontaneous HRV fluctuations are linked to functional changes in resting state brain activation in younger and older adults.

The vagus nerve connects the brain and the heart, allowing communication between the body and the mind. Studies have strengthened the meaning of the brain to control heart rate variability (HRV), however, brain research has largely overlooked the effects of age on the association between phasic changes in HRV and resting state functional brain connectivity. To close this gap, we studied a large open data set of 69 old and 134 young participants with two consecutive fMRI resting state scans in combination with the corresponding physiological HRV data assessed via photoplethysmography (PPG). We quantified spontaneous HRV changes from one resting state to the other and studied the unique information about the relationship between changes in functional coupling between brain areas and spontaneous HRV changes. Using a fc-MVPA, we identified functional brain coupling patterns associated with changes in HRV within brain networks, including the anterior cingulate cortex (ACC), the cerebellum, the brainstem, and the temporal lobe. These patterns were not significantly different between the two age groups - indicating age invariance of brain heart communication. Post hoc seed-to-voxel analyses indicated a stronger functional coupling of these identified clusters with brain regions such as the insula, the opercular cortex, the superior frontal gyrus, and the cerebellum when HRV increased. This pattern of findings is in accordance with prominent theories and provides further insights into the neural mechanisms underlying brain-heart communication.