Xiaolin Yu

Relationship between scalp potential and autonomic nervous activity during a mental arithmetic task

The cerebral cortex had massive bidirectional connections to autonomic nervous system and mental performance can induce change of autonomic activity, but which regions are related to autonomic function is not clear. The study was to analyze the scalp positions which may affect cardiac autonomic nervous activity during a mental arithmetic (MA) task. Forty-three healthy male subjects were voluntarily participated in the study. Sympathetic and parasympathetic activities were estimated with heart rate variability. Scalp potential was determined by the wavelet packet parameters and approximate entropy (ApEn) of Electroencephalogram (EEG). The results showed that heart rate and the normalized low frequency power component were significantly increased (p<0.01) and the high frequency power component was decreased (p<0.01). Meanwhile relative wavelet packet energy in alpha band of EEG at P3, P4, Pz, O1, O2 and Oz electrodes were decreased and the beta band of EEG at the same electrodes were increased significantly (p<0.01). ApEn was significantly increased in MA (p<0.01). Moreover, changes of brain activity were earlier than the changes of autonomic activity and significantly correlations existed between heart rate variability and wavelet packet energy (p<0.05). In addition, a significant positive correlation between HR change and the laterality ratio score of alpha band in P3 v P4 (p<0.05) were observed. It is noted that cerebral conscious activity enhanced with the decrease of parasympathetic activity and increase of sympathetic activity, and the right post-central areas dominated sympathetic activity during stress-inducing mental tasks.

Effects of mental tasks on the cardiorespiratory synchronization.

The cardiovascular and respiratory systems are functionally related to each other, but it is unclear if the cerebral cortex can affect their interaction. The effect of a mental task on the synchronization between cardiovascular and respiratory systems was investigated in the article. Electroencephalogram (EEG), electrocardiogram (ECG) and respiratory signal (RES) were collected from 29 healthy male subjects during the mental arithmetic (MA) task and the synchrogram was used to estimate the strength of cardiorespiratory synchronization. Our results showed that MA task significantly increased the breath rate, the heart rate and the EEG power spectral energy in theta band at FC3, FC4 and C4 electrodes (p<0.01), decreased the duration of cardiorespiratory synchronization epochs (p<0.05). Moreover the duration of cardiorespiratory synchronization epochs during MA task was negatively correlated with the EEG power spectral energy in theta band at FC3, FC4 and C4 electrodes and the sympathetic activity (p<0.05). The results demonstrated that ANS and cerebral cortex are implicated in the changes of cardiorespiratory synchronization during MA task.

Volitional control of the heart rate

The heart rate is largely under control of the autonomic nervous system. The aim of the present study is to investigate the interactions between the brain and heart underlying volitional control of the heart and to explore the effectiveness of volition as a strategy to control the heart rate without biofeedback. Twenty seven healthy male subjects voluntarily participated in the study and were instructed to decrease and increase their heart beats according to rhythmic, computer generated sound either 10% faster or slower than the subjects measured heart rate. Sympathetic and parasympathetic activities were estimated with the heart rate variability (HRV) obtained by power spectral analysis of RR intervals. Functional coupling patterns of cerebral cortex with the heart were determined by Partial directed coherence (PDC). In HR(slow) task; HR and sympathetic activity significantly decreased. However parasympathetic activity and power spectral density of EEG in low Alpha (8-10.5 Hz) band significantly increased. Moreover information flow from parietal area (P3 and P4) to RR interval significantly increased. During HR(quick) task; HR, sympathetic activity and power spectral density of EEG in low Beta (14-24 Hz) band significantly increased. Parasympathetic activity significantly decreased. Information flow from FT8, CZ and T8 electrodes to RR interval significantly increased. Our findings suggested that the heart beat can be controlled by volition and is related to some special areas in the cortex.

Cerebral and neural regulation of cardiovascular activity during mental stress

BackgroundMental arithmetic has been verified inducing cerebral and cardiovascular responses. However, the mechanism and sequential responses are still ambiguous. This study aims to reveal the mechanism of cardiovascular and autonomic responses and the related scalp positions that regulate the autonomic nerves system (ANS) during MA task.Methods34 healthy male subjects aged between 19 and 27xa0years old (mean age 23.6xa0±xa02.3xa0years) were recruited in. Electrocardiogram, impedance cardiography, beat-to-beat blood pressure and electroencephalography were measured simultaneously and continuously during the experiments. And the analysis of time–frequency, approximate entropy and Pearson correlation coefficient were adopted. For statistical comparison, paired t test is utilized in the study.ResultsThe results showed that mental arithmetic task increased heart rate (from 72.35xa0±xa01.88 to 80.38xa0±xa02.34), blood pressure (systolic blood pressure: from 112.09xa0±xa03.23 to 126.79xa0±xa03.44; diastolic blood pressure: from 74.15xa0±xa01.93 to 81.20xa0±xa01.97), and cardiac output (from 8.71xa0±xa00.30 to 9.68xa0±xa00.35), and the mental arithmetic induced physiological responses could be divided into two stages, the first stage (10–110xa0s) and late stage (150–250xa0s). The high frequency power component (HF) of HRV decreased during MA, but the normalized low frequency power component (nLF) and LF/HF ratio of HRV increased only at the late stage. Moreover, during first stage, the correlations between approximate entropy of electroencephalography at Fp2, Fz, F4, F7 and the corresponding time–frequency results of HF were significant. During the late stage, the correlations between approximate entropy of electroencephalography at Fp2, Fz, C3, C4 and the corresponding nLF was significant.ConclusionsOur results demonstrated that (1) mental stress induces time-dependent ANS activity and cardiovascular response. (2) Parasympathetic activity is lower during mental arithmetic task, but sympathetic nerve is activated only during late stage of mental arithmetic task. (3) Brain influences the cardiac activity through prefrontal and temporal cortex with the activation of ANS during mental arithmetic.

Causal interactions between the cerebral cortex and the autonomic nervous system

Mental states such as stress and anxiety can cause heart disease. On the other hand, meditation can improve cardiac performance. In this study, the heart rate variability, directed transfer function and corrected conditional entropy were used to investigate the effects of mental tasks on cardiac performance, and the functional coupling between the cerebral cortex and the heart. When subjects tried to decrease their heart rate by volition, the sympathetic nervous system was inhibited and the heart rate decreased. When subjects tried to increase their heart rate by volition, the parasympathetic nervous system was inhibited and the sympathetic nervous system was stimulated, and the heart rate increased. When autonomic nervous system activity was regulated by mental tasks, the information flow from the post-central areas to the pre-central areas of the cerebral cortex increased, and there was greater coupling between the brain and the heart. Use of directed transfer function and corrected conditional entropy techniques enabled analysis of electroencephalographic recordings, and of the information flow causing functional coupling between the brain and the heart.

Phase Synchronization and Spectral Coherence Analysis of EEG Activity During Mental Fatigue

In this article, 2 synchronization measures, phase locking value (PLV) and spectral coherence value (SCV), are used to characterize the changes of the phase synchronization and functional coupling of electroencephalogram (EEG) waves at different brain cortical areas for mental fatigue caused by a long-term cognitive task. The long-term cognitive task induces a significant decrease in the interhemispheric SCVs and PLVs of beta in central and parietal regions, a significant decrease in the intrahemispheric SCVs and PLVs of beta frequency band at the frontal–parietal and central–parietal, and frontal–central middle electrode pairs, suggesting EEG decreases in cooperative processing, strength of functional coupling, and flux of mutual information exchange in the corresponding inter- and intrahemispheres. However, when the mental fatigue level increases, the interhemispheric PLVs of theta are enhanced in the frontal region and C3–Cz electrode pair, and the intrahemispheric PLVs of theta are heightened at frontal–central middle electrode pairs. PLV and SCV measures could reflect the changes of the phase synchronization and functional coupling of EEG waves from time and frequency domains, which are sensitive to mental fatigue. Therefore, PLVs and SCVs can provide an effective and reliable way to quantify brain response to mental fatigue.

Effects of different stresses on cardiac autonomic control and cardiovascular coupling

The objective of this study was to investigate the impacts of different stresses on time-varying autonomic reactivity and cardiovascular coupling. In total, 25 male subjects were recruited. RR intervals (RRI), systolic and diastolic blood pressure (SBP, DBP), stroke volume (SV), cardiac output (CO), and systemic vascular resistance (SVR) values were collected during rest, mental arithmetic task (MAT), and cold pressor test (CPT). Baroreflex sensitivity (BRS) was derived using the transfer function method. Continuous wavelet transformation of RRI was used to describe the time-variant patterns of autonomic neural activities. Wavelet cross correlation and phase synchronization were used to estimate the amplitude and phase coupling between RRI and SBP. MAT was characterized by increased heart rate (HR), SBP, DBP, and CO with decreased BRS attributable to prolonged parasympathetic withdrawal. Moreover, cardiovascular coupling was disrupted in MAT. These results indicated that baroreflex was depressed, and the top-down system started to take action under mental stress. In CPT, SBP, DBP, and SVR increased significantly, whereas HR and BRS remained unchanged. The increase of sympathetic activity was transient, and cardiovascular coupling did not change in CPT. Intriguingly, the frequency of the maximum cross-correlation coefficient in the low-frequency band (0.04-0.15 Hz) was significantly decreased in CPT, which may be due to the change of resonance frequency of the baroreflex loop.NEW & NOTEWORTHY The study is the first to compare the time-variant pattern of autonomic nervous activities and cardiovascular coupling between the mental arithmetic task (MAT) and the cold pressor test (CPT). Our results demonstrated that MAT and CPT elicited different time-varying patterns of autonomic neural activities and cardiovascular synchronization. Both the amplitude and phase consistency of blood pressure and heart rate decreased in MAT. CPT may affect the harmonic frequency of the baroreflex loop.

Volitional Control of Heartbeat and Its Dependence on Pallium

It is believed that we cannot change our heart rhythm by will because the heartbeat is mainly controlled by the autonomic nervous system (ANS), which cannot be affected directly by subjective will. An experiment was designed to determine whether the heartbeat and ANS could be controlled by volition, and, if it is true, how they were controlled. It was demonstrated that the ANS could be partly controlled by volition. The volition, which tended to slow down the heartbeat, initiated synchronized activity in the medial prefrontal cortex, inhibited the sympathetic system, and then decreased the heartbeat. On the other hand, another kind of volition, which sped up the heartbeat, initiated desynchronized activity at the precentral, central, parietal, and occipital regions, inhibited the parasympathetic system and excited the sympathetic system, and then increased the heartbeat. Moreover, information flow from posterior cortex to anterior cortex was observed during the experiment. The parietal area played an important role in triggering the sensorimotor cortex and integrating the information, and the information flow from the central and precentral cortex to heart was dominant. All that demonstrated that volition can partly control the heartbeat, but the behavior was different from the motor nervous system.

Estimation of the cortico-cortical and brain-heart functional coupling with directed transfer function and corrected conditional entropy

Abstract The brain activity involved mental stress can increase the risk of sudden cardiac death in patients with organic and ischemic heart disease. Thus, the interaction between the senior nerve and autonomic nerve has recently been given more attention. The purpose of this study was to analyze the cortico-cortical functional coupling and direction of information flow between the brain and heart during a mental arithmetic (MA) task. Forty-three healthy male volunteer participated in the study. Functional coupling patterns of cerebral cortex and heart activity were determined by directed transfer function (DTF) and corrected conditional entropy (CCE). The experimental results showed that sympathetic activity increased, parasympathetic activity and heart rate variability (HRV) decreased, and the heart rate increased during the was quickened by MA task. Furthermore, a reciprocal pattern was observed in the changes of the autonomic nervous system. Meanwhile, cortico-cortical functional coupling was stronger during the MA task. Activity directed to post-central areas of brain and heart localized to the C4 and Cz regions. Our findings suggest that a stress-inducing mental task may cause an increase in the coupling of brain regions and an increase in heart rate though the increase of sympathetic activity.