Confounding effects of heart rate, breathing rate, and frontal fNIRS on interoception

Abstract

Recent studies have established that cardiac and respiratory phases can modulate perception and related neural dynamics. While heart rate and respiratory sinus arrhythmia are possibly affecting interoception biomarkers, such as heartbeat-evoked potentials, the relative changes in heart rate and cardiorespiratory dynamics in interoceptive processes have not yet been investigated. In this study, we investigated the variation in heart and respiration rates, as well as higher functional dynamics including cardiorespiratory correlation and frontal hemodynamics, during cardiac awareness tasks. To further investigate the functional physiology linked to changes in vagal activity caused by specific respiratory rates, we studied cardiac awareness and controlled respiration rate. The results demonstrate that focusing on heartbeats decreases respiration and heart rates in comparison, which may be part of the physiological mechanisms related to 'listening' to the heart, the focus of attention, and self-awareness. Focusing on heartbeats was also observed to increase frontal connectivity, supporting the role of frontal structures in the neural monitoring of visceral inputs. However, cardiorespiratory correlation is affected by both interoceptive and controlled respiration. Based on these results, we concluded that variations in heart and respiratory rates are confounding factors in the assessment of interoceptive abilities and relative fluctuations in respiration and heart rates should be considered to be a mode of covariate measurement of interoceptive processes.

Brain-heart interactions in the neurobiology of consciousness

“…The level of interoceptive awareness has been mostly quantified through different tasks of heartbeats' sensation [48][49][50][51]. The validity of some of those tasks has been questioned because of different biases related to the specificity of the measurements [52,53], and because of confounding factors [54,55]. The reported links between atypical or disrupted interoceptive ability include different pathological conditions [19,26], but also in abnormal emotion regulation [56], emotion sensitivity/recognition [57], emotion categorization [58], and overall emotional processing [59].…”