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 possibly affect 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 breathing rates, as well as higher functional dynamics including cardiorespiratory correlation and frontal hemodynamics measured with fNIRS, during a heartbeat counting task. To further investigate the functional physiology linked to changes in vagal activity caused by specific breathing rates, we performed the heartbeat counting task together with a controlled breathing rate task. The results demonstrate that focusing on heartbeats decreases breathing 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 heartbeats counting and controlled breathing tasks. Based on these results, we concluded that variations in heart and breathing rates are confounding factors in the assessment of interoceptive abilities and relative fluctuations in breathing and heart rates should be considered to be a mode of covariate measurement of interoceptive processes.

Dynamic fluctuations in ascending heart–to–brain communication under mental stress

“…The self-assessment measurements we used for subjective stress evaluation do not refer to a specific psychometric test. Moreover, we are aware that confounding factors and artifact sources are numerous in EEG and therefore in functional brain-heart interplay studies (106)(107)(108)., In particular, the gamma activity is quite sensitive to muscle artifacts. Since simultaneously electromyography recordings were not available, we cannot exclude that all of the artifacts have been rejected in our pre-processing stage.…”

Changes in the heartbeat-evoked potential under ventricular fibrillation: a near-death case report

“…The confounding factors present in brain-heart interaction studies are numerous 20,24,41 . These factors can be controlled by simultaneously monitoring other physiological activities, such as breathing rate, temperature, skin conductance, or blood pressure.…”

“…EEG spectrogram was computed using short-time Fourier transform with a sliding time window of 2 s with a 50% overlap. Time-varying EEG oscillations were integrated within the ranges delta (1-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), beta (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), and gamma (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45).…”

Correlation and asynchronization of electroencephalogram and cerebral blood flow in active and passive stimulations

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