Biology subjects

Candia-Rivera, D.

Publications and source records attributed to Candia-Rivera, D..

4 recordsLinked to original sources

bioRxiv2022

Dynamic fluctuations in ascending heart-to-brain modulations under mental stress elicitation

Dynamical information exchange between central and autonomic nervous systems, as referred to functional brain-heart interplay, occurs during emotional and physical arousal. It is well documented that physical and mental stress lead to sympathetic activation. Nevertheless, the role of autonomic inputs in nervous-system-wise communication under mental stress is yet unknown. In this study, we estimated the causal and bidirectional neural modulations between EEG oscillations and peripheral sympathetic and parasympathetic activities using a recently proposed computational framework for a functional brain-heart interplay assessment, namely the sympathovagal synthetic data generation model. Mental stress was elicited in 37 healthy volunteers by increasing their cognitive demands throughout three tasks associated with increased stress levels. Stress elicitation induced an increased variability in sympathovagal markers, as well as increased variability in the directional brain-heart interplay. The observed heart-to-brain interplay was primarily from sympathetic activity targeting a wide range of EEG oscillations, whereas variability in the efferent direction seemed mainly related to EEG oscillations in the gamma band. These findings extend current knowledge on stress physiology, which mainly referred to top-down neural dynamics. Our results suggest that mental stress may not cause an increase in sympathetic activity exclusively as it initiates a dynamic fluctuation within brain-body networks including bidirectional interactions at a brain-heart level. We conclude that directional brain-heart interplay measurements may provide suitable biomarkers for a quantitative stress assessment and bodily feedback may modulate the perceived stress caused by increased cognitive demand.

neuroscience↗

bioRxiv2022

Nonlinear Neural Patterns Are Revealed In High Frequency fNIRS Analysis

Vasomotor tone has a direct implication in oxygen transport to neural tissue, and its dynamics are known to be under constant control from feedback loops with visceral signals, such as sympathovagal interactions. Functional Near Infrared Spectroscopy (fNIRS) offers a nuanced measure of hemoglobin concentration that also comprises high frequencies, though most fNIRS literature studies traditional frequency ranges of hemodynamics (< 0.2 Hz). Linear theory of the hemodynamic response function supports this low frequency band, but we hypothesize that nonlinear effects elicited from the complex system sustaining vasomotor tone presents itself in higher frequencies. To characterize these effects, we investigate how plausible modulation of autoregulatory effects impact aforementioned high frequency components of fNIRS through simulations of mechanistic hemodynamic models. Then, we compare representational similarities between fast (0.2 Hz to 0.6 Hz) and slow (< 0.2 Hz) wave fNIRS to demonstrate that representations acquired through nonlinear analysis are distinct between the frequency bands, whereas when using linear time-domain analysis they are not. Furthermore, by comparing topoplots of significant detectors using nonlinear random vector correlation methods (distance correlation), we demonstrate through a 2nd level group analysis that the median concentrations acquired by fNIRS are independent when analyzing the nonlinearity of their dynamics in their fast and slow component, while they are dependent when utilizing linear time-domain analysis. This study not only provides motivation for researchers to also include higher frequency components in their analysis, but also provides motivation to explore nonlinear effects, e.g. topological entropy. The results of this study motivate future research to explore the nonlinear autoregulatory impacts of regional blood flow and hemoglobin concentrations. Author summaryConventionally, hemodynamic response from induced neural metabolic demand is studied as a slow signal, i.e < 0.2 Hz. Though this may be justified in linear analysis of hemodynamics, vascular mechanics nonlinearly transform the neural metabolic demand to hemodynamic response, where a nonlinear spectral profile may show higher frequency responses. Higher frequency ranges may give insight into local vascular dynamics, particularly their reflection of autoregulatory phenomena, hypothesized to be controlled by sympathovagal feedback loops, thus opening a new avenue for studying brain-body interactions. Functional near infrared spectroscopy (fNIRS) offers a method with high temporal resolution (10 Hz) for observing these effects in hemoglobin concentrations. In this study, we utilize stochastic dynamical simulations of plausible autoregulatory phenomena and an open fNIRS dataset to study differences of fast and slow wave neurovascular representations. We demonstrate that, while linear time-domain analysis provides similar representations of fast and slow wave activity, representations derived from nonlinear methods are not. Furthermore, we show how stress tasks, which may elicit autonomic activity, further desynchronizes nonlinear activity between fast and slow wave signals compared to a non-stress inducing task, demonstrating unique high frequency neurovascular phenomena that is mediated by stress processing.

neuroscience↗

bioRxiv2022

Effects of neural monitoring and control of visceral signals on heart rate, respiration rate, and frontal hemodynamics

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.

neuroscience↗

bioRxiv2021

Cardiac sympathovagal activity initiates a functional brain-body response to emotional processing

A century-long debate on bodily states and emotions persists. While the involvement of bodily activity in emotion physiology is widely recognized, the specificity and causal role of such activity related to brain dynamics has not yet been demonstrated. We hypothesize that the peripheral neural monitoring and control of cardiovascular activity prompts and sustains brain dynamics during an emotional experience, so these afferent inputs are processed by the brain by triggering a concurrent efferent information transfer to the body. To this end, we investigated the functional brain-heart interplay under emotion elicitation in publicly available data from 62 healthy participants using a computational model based on synthetic data generation of EEG and ECG signals. Our findings show that sympathovagal activity plays a leading and causal role in initiating the emotional response, in which ascending modulations from vagal activity precede neural dynamics and correlate to the reported level of arousal. The subsequent dynamic interplay observed between the central and autonomic nervous systems sustains emotional processing. These findings should be particularly revealing for the psychophysiology and neuroscience of emotions. SignificanceWe investigate the temporal dynamics of brain and cardiac activities in healthy subjects who underwent an emotional elicitation through videos. We demonstrate that, within the first few seconds, emotional stimuli modulate the heart activity, which in turn stimulate an emotion-specific cortical response in the brain. Then, the conscious emotional experience is sustained by a bidirectional brain-heart interplay and information exchange. Moreover, the perceived intensity of an emotional stimulus is predicted by the intensity of neural control regulating the heart activity. These findings may constitute the fundamental knowledge linking neurophysiology and psychiatric disorders, including the link between depressive symptoms and cardiovascular disorders.

neuroscience↗