Alterations in heart-brain interactions under mild stress during a cognitive task are reflected in entropy of heart rate dynamics

Abstract

Many people experience mild stress in modern society which raises the need for an improved understanding of psychophysiological responses to stressors. Heart rate variability (HRV) may be associated with a flexible network of intricate neural structures which are dynamically organized to cope with diverse challenges. HRV was obtained in thirty-three healthy participants performing a cognitive task both with and without added stressors. Markers of neural autonomic control and neurovisceral complexity (entropy) were computed from HRV time series. Based on individual anxiety responses to the experimental stressors, two subgroups were identified: anxiety responders and non-responders. While both vagal and entropy markers rose during the cognitive task alone in both subgroups, only entropy decreased when stressors were added and exclusively in anxiety responders. We conclude that entropy may be a promising marker of cognitive tasks and acute mild stress. It brings out a new central question: why is entropy the only marker affected by mild stress? Based on the neurovisceral integration model, we hypothesized that neurophysiological complexity may be altered by mild stress, which is reflected in entropy of the cardiac output signal. The putative role of the amygdala during mild stress, in modulating the complexity of a coordinated neural network linking brain to heart, is discussed.

Balance control is impaired by mental fatigue due to the fulfilment of a continuous cognitive task or by the watching of a documentary

“…Another limitation of this study was the lack of data about the physiological responses to the experimental conditions. Performing a prolonged continuous demanding cognitive task which induces MF can also cause an acute stress (Blons et al 2019), which is likely to affect balance control (Doumas et al 2018). Since an acute stress have cardiovascular consequences that can be assessed through heart rate variability (Blons et al 2019), future studies about the effects of MF on balance control should include an assessment of heart rate variability to specify the impact of MF-related stress on balance control.…”

Entropy in Heart Rate Dynamics Reflects How HRV-Biofeedback Training Improves Neurovisceral Complexity during Stress-Cognition Interactions

“…Here, the overall degree of complexity of HRV signals was calculated by integrating the values of sample entropy that were obtained over the shortest scales, which corresponds to the above described vagal control of heart rate. Refined composite multiscale entropy (RCMSE) improved the accuracy of MSE by reducing the probability of inducing undefined entropy, which is especially useful when analyzing the short time series of cardiovascular dynamics [ 23 ], as recently shown [ 44 ]. Detailed methods for computing MSE and RCMSE can be found, respectively, in [ 45 ] and [ 44 , 46 ].…”

“…In agreement with the above assumption, the main observation is that complexity in heartbeat dynamics grows with brain activity, but vanished with stress. Further, multiscale entropy in HRV has been suggested as a reliable marker of coordinated neurovisceral integration during stress-cognition interactions [ 23 ], although this is a new recent hypothesis that should be addressed further, by manipulating e.g ., stress management. While the response to stress in humans is a healthy adaptive function in situations of acute challenge, a prolonged exposure to stressors might cause persistent dysregulations [ 12 ], which affects the CAN, as reflected in a systematically blunted vagal tone [ 24 , 25 ].…”

Heart Rate Variability in Psychology: A Review of HRV Indices and an Analysis Tutorial

“…Compared to single-scale entropy estimates, MSE has been able to accurately account for lower HRV observed in different cardiac abnormalities, such as atrial fibrillation where there are random outputs in HRV [83]. As MSE formulation does not allow for reliable computation of entropy in short time windows, new methods such as refined MSE (RMSE) [84] and refined composite MSE (RCMSE) [85] have been introduced, though few studies have tested them on HRV [86,87].…”