Index Of Sympathetic Activity Research Articles

Classification of Dichotomous Emotional States Using Electrodermal Activity Signals and Multispectral Analysis.

In this work, an analysis based on complex demodulation is proposed to classify dichotomous emotional states using Electrodermal activity (EDA) signals. For this, annotated happy and sad EDA is obtained from an online public database. The sympathetic activity indices, namely Time-varying (TVSymp) and Modified TVSymp, are computed from the reconstructed EDA signal. Further, the derivative of phasic EDA is calculated from the phasic component obtained using the convex optimization (cvxEDA) based EDA decomposition method. Five statistical features are computed from each index and used for the classification. The results of the classification indicate that these features are capable of differentiating happy and sad emotional states with 75% accuracy. This technique could be effective in the identification of clinical disorders associated with happy and sad emotional states.

Reliability of Heart Rate Variability during Polysomnographic Sleep

Spectral analysis of heart rate variability (HRV) is often used as a noninvasive index of cardiac sympathetic and/or parasympathetic activity during sleep. During controlled wake recordings, the low frequency (LF) component of HRV can be unreliable within experimental sessions and against other direct sympathetic measurements. In contrast, the high frequency (HF) component of HRV has higher reported reproducibility within controlled wake sessions. It remains unknown if the frequency component of HRV is reliable across sleep cycles within individuals during stable sleep. The purpose of the present study was to determine HRV reliability during stable stage II (N2) sleep, slow wave sleep (SWS) and rapid eye movement (REM) sleep. We hypothesized that both LF and HF components of HRV would be less reliable during REM sleep than during SWS and N2 sleep. Twenty‐seven participants (11 male, 16 female, 26±1 years, 27±1 kg/m2) were enrolled in the present study. Overnight polysomnography (PSG; NATUS, Middleton, WI) and continuous two‐lead electrocardiography (ECG) were recorded during an 8‐hour sleep opportunity. The nocturnal ECG recordings were imported into a custom software (WinCPRS, Absolute Aliens, Finland) for analysis of HRV via fast‐Fourier transformation function. Autonomic cardiac activity was quantified as LF (0.04‐0.15 Hz) and HF (0.15‐0.4 Hz) HRV. Two separate stable periods of sleep (range, 5‐10 min) absent of cortical arousal were selected from each sleep stage for comparison. Raw LF and HF HRV underwent logarithmic transformation due to non‐normal distribution. Statistical analysis included bivariate correlation of HRV across differing sleep stage cycles (α = 0.05). LF HRV was significantly correlated across two independent sleep cycles in N2 (r=0.694, p<0.001, n=26), SWS (r=0.765, p<0.001, n=25), and REM sleep (r=0.699, p<0.001, n=20). Similarly, HF HRV was reliable across two independent sleep cycles in N2 sleep (r=0.839, p<0.001, n=26), SWS (r=0.765, p<0.001, n=25), and REM sleep (r=0.881 p<0.001, n=21). Taken together, both LF and HF HRV measures were reliable across stable N2, SWS, and REM sleep. Our results support the reliability of frequency domain analysis of HRV during key PSG sleep stages within a single night, but further research across nights is warranted.

Different Relationship Between Glycemic Status and Autonomic Function in Patients with Type 2 Diabetes Mellitus and in Healthy Controls

Autonomic neuropathy is a common complication in diabetes mellitus (DM). Decreased vagal nerve activity and augmented sympathetic nerve activity have been reported in patients with DM. However, the relationship between autonomic function and glycemic status in DM and in individuals without DM remains unclear. We hypothesized that indices of sympathetic and vagal nerve activity are related to glycemic status. Eleven patients who were clinically diagnosed with type‐2 DM (HbA1c, 6.8 ± 0.3%; age, 54 ± 3 yrs), and 20 healthy non‐DM individuals (including 10 pre‐DM; HbA1c < 6.5%; range 5.1‐6.1%; age, 59 ± 2 yrs) were studied (19 male, 12 female). Five DM patients had hypertension. Patients with DM and hypertensives were treated with standard medications. Beat‐by‐beat blood pressure (BP), heart rate (HR) and muscle sympathetic nerve activity (MSNA) were recorded under resting conditions. HR variability (HRV) was calculated and spontaneous cardiovagal baroreflex sensitivity (CBRS) was evaluated with the sequence method. CBRS in DM was lower than in non‐DM subjects (P < 0.05). MSNA in DM was also lower than in non‐DM subjects (P < 0.05). In linear regression analyses with data from all subjects, CBRS was negatively correlated with fasting blood glucose (FBG) (R = ‐0.47), insulin (R = ‐0.42), and homeostasis model assessment of insulin resistance (HOMA‐IR) (R = ‐0.43) (P < 0.05 for all). MSNA was negatively correlated with HbA1c and HOMA‐IR (R = ‐0.41, ‐0.42, respectively; both, P < 0.05). The high frequency (HF) component of HRV (i.e., an index of vagal tone) was negatively correlated with insulin (R = ‐0.46) and HOMA‐IR (R = ‐0.42) in all subjects (P < 0.05 for both). In non‐DM subjects, CBRS was negatively correlated with FBG (R = ‐0.53, P <0.05). HF was negatively correlated with FBG (R = ‐0.51), insulin (R = ‐0.66), and HOMA‐IR (R = ‐0.66) (P < 0.05 for all), but MSNA was not correlated with glycemic/insulin status in non‐DM subjects. Whereas in DM patients, MSNA tended to be negatively correlated with HOMA‐IR (R = ‐0.77, P = 0.07). In the present study, both MSNA and vagal activity (CBRS and HF) were decreased in relation to the glycemic/insulin status. Vagal nerve activity was associated with the glycemic/insulin status even in non‐DM subjects (i.e., healthy and pre‐DM). Based on these results, we speculate that both vagal and sympathetic nerves were injured by DM progression, and that vagal neuropathy preceded the sympathetic neuropathy. Our results differ from prior reports that showed that MSNA in DM was higher than in non‐DM. However, in our study subjects, the severity of DM was mild, and except for hypertension in 5 subjects, none had manifestations of diabetic end‐organ damage. Differences in the duration and severity of DM as well as the effects of the treatments could contribute to the differences in the results. Further studies on the autonomic function during the DM progression are warranted.

Relationships between muscle sympathetic nerve activity and novel indices of arterial stiffness using single oscillometric cuff in patients with hypertension.

The arterial velocity pulse index (AVI) and arterial pressure‐volume index (API) have been proposed as new arterial stiffness indices that can be measured using an oscillometric cuff. Sympathetic nerve activity (SNA) contributes to arterial stiffness via increasing vascular smooth muscle tone. However, the associations between SNA and the AVI or API are not understood. The purpose of this study was to evaluate the relationships between muscle sympathetic nerve activity (MSNA) and the AVI or API in healthy individuals and patients with hypertension (HT). Forty healthy individuals (40.1 ± 15.2 years, 8 females) (healthy group) and 40 patients with HT (60.2 ± 13.6, 18 females) (HT group) were included in this study. The AVI, API, MSNA, beat‐by‐beat blood pressure, and heart rate were recorded simultaneously. The AVI and API were higher in the HT group than in the healthy group (AVI, 26.1 ± 7.6 vs. 16.5 ± 4.0, p < 0.001; API, 31.2 ± 8.6 vs. 25.5 ± 7.2, p = 0.002). MSNA in the HT group was also higher than in the healthy group (p < 0.001). MSNA was correlated with the AVI, but not with the API, in both the healthy group (R = 0.52, p = 0.001) and HT group (R = 0.57, p < 0.001). MSNA was independently correlated with the AVI in multivariate analysis (ß = 0.34, p = 0.001). In conclusion, AVI, obtained by a simple and less user‐dependent method, was related to the MSNA in healthy individuals and patients with HT.

Music Modulates Autonomic Nervous System Activity in Human Fetuses.

ContextFetal Autonomic Nervous sysTem Evaluation (FANTE) is a non-invasive tool that evaluates the autonomic nervous system activity in a fetus. Autonomic nervous system maturation and development during prenatal life are pivotal for the survival and neuropsychiatric development of the baby.ObjectiveAim of the study is to evaluate the effect of music stimulation on fetal heart rate and specific parameters linked to ANS activity, in particular fetal heart rate variability.MethodsThirty-two women between the 32nd and 38th week with a singleton uncomplicated pregnancy were recruited. All FANTE data collections were acquired using a 10-derivation electrocardiograph placed on the maternal abdomen. In each session (5 min basal, 10 min with music stimulus, and 5 min post-stimulus), FANTE was registered. The music stimulus was “Clair de lune” Debussy, played through headphones on the mother’s abdomen (CTR: 31927).ResultsMusic does not change the mean value of fetal heart rate. However, indices of total fetal heart rate variability statistically increase (RRsd p = 0.037, ANNsd p = 0.039, SD2 p = 0.019) during music stimulation in comparison to the basal phase. Heart rate variability increase depends mainly on the activation of parasympathetic branches (CVI p = 0.013), meanwhile, no significant changes from basal to stimulation phase were observed for indices of sympathetic activity. All the parameters of heart rate variability and parasympathetic activity remained activated in the post-stimulus phase compared to the stimulus phase. In the post-stimulus phase, sympathetic activity resulted in a significant reduction (LFn p = 0.037).ConclusionMusic can influence the basal activity of the fetal autonomic nervous system, enhancing heart rate variability, without changing fetal heart rate mean value. Music is enabled to induce a relaxation state in a near-to-term fetus, mediated by parasympathetic activation and by a parallel sympathetic inhibition.

The impact of social disadvantage on autonomic physiology of latinx adolescents: The role of environmental risks.

The experience of poverty embodies complex, multidimensional stressors that may adversely affect physiological and psychological domains of functioning. Compounded by racial/ethnic discrimination, the financial aspect of family poverty typically coincides with additional social and physical environmental risks such as pollution exposure, housing burden, elevated neighborhood unemployment, and lower neighborhood education levels. In this study, we investigated the associations of multidimensional social disadvantage throughout adolescence with autonomic nervous system (ANS) functioning at 17 years. Two hundred and twenty nine low-income Mexican-American adolescents (48.6% female) and their parents were assessed annually between the ages of 10 and 16. Participants' census tracts were matched with corresponding annual administrative data of neighborhood housing burden, education, unemployment, drinking water quality, and fine particulate matter. We combined measures of adolescents' electrodermal response and respiratory sinuses arrhythmia at rest and during a social exclusion challenge (Cyberball) to use as ANS indices of sympathetic and parasympathetic activity, respectively. Controlling for family income-to-needs, youth exposed to greater cumulative water and air pollution from ages 10-16 displayed altered patterns of autonomic functioning at rest and during the social challenge. Conversely, youth living in areas with higher housing burden displayed healthy patterns of autonomic functioning. Altogether, results suggest that toxin exposure in youths' physical environments disrupts the ANS, representing a plausible mechanism by which pollutants and social disadvantage influence later physical and mental health.

Heart Rate Variability and Sympathetic Activity Is Modulated by Very Low-Calorie Ketogenic Diet.

Obesity is characterized by an energy imbalance and by the accumulation of visceral adipose tissue. The energy balance is controlled by a complex set of balanced physiological systems that provide hunger and satiety signals to the brain and regulate the body’s ability to consume energy. The central nervous system controls the metabolic state, influencing the activity of other systems and receiving information from them. Heart rate variability (HRV) is the natural variability of the heart rate in response to several factors. HRV is related to the interaction between the SNS and the parasympathetic. In the light of this evidence, the aim of this study is to investigate the possible effects of the two different dietary regimens such as very low-calorie ketogenic diet (VLCKD) vs. low caloric diet (LCD), on the functions of the nervous system, with particular attention to the autonomous control of heart rate variability (HRV). A total of 26 obese subjects underwent diet therapy in order to reduce body weight; they were also randomly divided into two groups: the VLCKD group and the LCD group. Our results showed that in both groups, there is a reduction in heart rate as an indicator of sympathetic activity; we found a statistically significant variation only in the VLCKD group. Therefore, this study supports the notion that the sympathovagal balance can be modulated by a specific diet, but further studies are needed to clarify the molecular pathway undergoing this modulation.

Validation of a new impedance cardiography analysis algorithm for clinical classification of stress states.

Pre-ejection period (PEP) is an index of sympathetic nervous system activity that can be computed from electrocardiogram (ECG) and impedance cardiogram (ICG) signals, but sensitive to speech/motion artifact. We sought to validate an ICG noise removal method, three-stage ensemble-average algorithm (TEA), in data acquired from a clinical trial comparing active versus sham non-invasive vagal nerve stimulation (tcVNS) after standardized speech stress. We first compared TEA's performance versus the standard conventional ensemble-average algorithm (CEA) approach to classify noisy ICG segments. We then analyzed ECG and ICG data to measure PEP and compared group-level differences in stress states with each approach. We evaluated 45 individuals, of whom 23 had post-traumatic stress disorder (PTSD). We found that the TEA approach identified artifact-corrupted beats with intraclass correlation coefficient>0.99 compared to expert adjudication. TEA also resulted in higher group-level differences in PEP between stress states than CEA. PEP values were lower in the speech stress (vs. baseline rest) group using both techniques, but the differences were greater using TEA (12.1ms) than CEA (8.0ms). PEP differences in groups divided by PTSD status and tcVNS (active vs. sham) were also greater when using the TEA versus CEA method, although the magnitude of the differences was lower. In conclusion, TEA helps to accurately identify noisy ICG beats during speaking stress, and this increased accuracy improves sensitivity to group-level differences in stress states compared to CEA, suggesting greater clinical utility.

A novel assessment of spontaneous laughter under free-living condition based on heart rate, acceleration, and autonomic nerve activity

The present investigation aimed to develop a novel method of spontaneous laughter (SL) assessment based on heart rate variability (HRV) and lumbar accelerometry under free-living conditions. The subjects of the present investigation were ten healthy young men. The investigation consisted of three 15-min experimental periods after the resting period and 5 h of free-living conditions. The three experimental periods included light-intensity aerobic exercise (LAE), moderate-intensity aerobic exercise (MAE), or watching comedy movie inducing SL (SLA), and were randomly ordered across three separate days. During SLA, the subjects watched comedy movies. The autonomic nervous system (ANS) activity was measured using continuous heart rate (HR) responses over the investigation period; the total power, low frequency (LF: 0.035 to 0.15 Hz), and high frequency (HF: 0.15 to 0.4) components were obtained using frequency analysis. The LF and HF were normalized by total power (nHF, nLF), and the LF was divided by HF to obtain a sympathetic activity index (LF/HF). SLA increased sympathetic nerve activity without an increase in heart rate compared to the resting state. The results of the preset investigation suggested that the combination of acceleration with heart rate and the autonomic nerve activity can improve the accuracy for estimating the SLA under the free-living condition.

Stand Up to Excite the Spine: Neuromuscular, Autonomic, and Cardiometabolic Responses During Motor Imagery in Standing vs. Sitting Posture.

Motor imagery (MI) for health and performance strategies has gained interest in recent decades. Nevertheless, there are still no studies that have comprehensively investigated the physiological responses during MI, and no one questions the influence of low-level contraction on these responses. Thus, the aim of the present study was to investigate the neuromuscular, autonomic nervous system (ANS), and cardiometabolic changes associated with an acute bout of MI practice in sitting and standing condition. Twelve young healthy males (26.3 ± 4.4 years) participated in two experimental sessions (control vs. MI) consisting of two postural conditions (sitting vs. standing). ANS, hemodynamic and respiratory parameters, body sway parameters, and electromyography activity were continuously recorded, while neuromuscular parameters were recorded on the right triceps surae muscles before and after performing the postural conditions. While MI showed no effect on ANS, the standing posture increased the indices of sympathetic system activity and decreased those of the parasympathetic system (p < 0.05). Moreover, MI during standing induced greater spinal excitability compared to sitting posture (p < 0.05), which was accompanied with greater oxygen consumption, energy expenditure, ventilation, and lower cardiac output (p < 0.05). Asking individuals to perform MI of an isometric contraction while standing allows them to mentally focus on the motor command, not challenge balance, and produce specific cardiometabolic responses. Therefore, these results provide further evidence of posture and MI-related modulation of spinal excitability with additional autonomic and cardiometabolic responses in healthy young men.

The ratio of heart rate to heart rate variability reflects sympathetic activity during incremental cycling exercise

ABSTRACT A low-frequency to a high-frequency component ratio (LF/HF) in heart rate variability (HRV) may not accurately reflect sympathetic nervous activity during exercise. Thus, a valid HRV-based index of sympathetic nervous activity is needed. Therefore, the heart rate to LF ratio (Heart rate/LF) was evaluated as sympathetic nervous activity index which is reflected by catecholamine levels during incremental exercise. In this study, 15 healthy adults performed an incremental exercise test using a cycle ergometer. HRV was derived from electrocardiography and HRV components related to the autonomic nervous system were obtained using frequency analysis. Heart rate/LF was calculated using the heart rate and LF component produced by HRV analysis. Catecholamine, blood lactate levels and respiratory gas were also measured throughout the exercise test. While LF/HF did not increase with increasing exercise intensity, Heart rate/LF non-linearly increased during the incremental exercise test, as did noradrenaline and blood lactate. Interestingly, Heart rate/LF values were positively correlated with noradrenaline (ρ = 0.788, p < 0.05) and blood lactate (ρ = 0.802, p < 0.05) levels and carbon dioxide production (ρ = 0.903, p < 0.05) from at rest through the exercise stages. Heart rate/LF reflects sympathetic nervous activity and metabolic responses during incremental cycling exercise and has potential as an HRV index of sympathetic nervous activity during exercise. Trial registration: UMIN Japan identifier: UMIN000039639..

Autonomic Responses during Labor: Potential Implications for Takotsubo Syndrome

Takotsubo syndrome is a serious complication of labor. Although the pathophysiologic role of excessive sympathetic activation is established in this process, concurrent vagal responses have not been adequately described. Moreover, it remains unclear whether autonomic activity depends on the mode of delivery. Here, we explored the hypothesis that the different management of cesarean and vaginal delivery may elicit diverse responses affecting both autonomic arms. For this aim, continuous electrocardiographic recording was performed in 20 women during labor, and non-invasive indices of sympathetic and vagal activity were compared between the two modes of delivery. We report sympathetic prevalence during cesarean delivery, caused by marked vagal withdrawal, whereas autonomic activity was rather stable during vaginal delivery. These differences may be attributed to the effects of anesthesia during cesarean delivery, along with the protective effects of oxytocin administration during vaginal delivery. Our results provide further insights on autonomic responses during labor that may prove useful in the prevention of complications, such as takotsubo syndrome.

Resting autonomic activity in adults who stutter and its association with self-reports of social anxiety

PurposeThe purpose of this study was to investigate resting autonomic activity in adults who stutter (AWS) compared to adults who do not stutter (ANS) and the relationship this has on self-reports of social anxiety. MethodsThirteen AWS and 15 ANS completed the Social Interaction Anxiety Scale (SIAS; Mattick & Clark, 1998) and Brief Fear of Negative Evaluation (BFNE; Leary, 1983). Following this, measures of skin conductance levels (i.e. index of sympathetic activity) and respiratory sinus arrhythmia (i.e. index of parasympathetic activity) were taken during a 5-minute resting, baseline period. Independent sample t tests were used to assess differences between groups on self-reports of anxiety (SIAS, BFNE) and resting autonomic levels (SCL, RSA). Separate multiple regression analyses were performed in order to assess the relationship between self-reports of anxiety and autonomic measures. ResultsResults showed significantly higher mean SCL and lower mean RSA levels in the AWS compared to the ANS at resting, baseline. Regression analysis showed that self-reports from the SIAS had a significant effect on RSA levels for the AWS but not the ANS. No significant effects were found for BFNE on RSA. Nor was there a significant effect from SIAS or BFNE on SCL levels for either group. ConclusionFindings suggest that resting RSA levels may be a physiological marker for social anxiety levels in adults who stutter.

Short-Term Fasting and Ingestion of Caloric Drinks Affect Heartbeat-Evoked Potentials and Autonomic Nervous System Activity in Males

Central nervous systems receive and process information from the internal and external environment to maintain homeostasis. This includes interoceptive awareness of the organism’s nutritional state. Whenever food supply is required, feelings of hunger initiate the search for and the consumption of appropriate amounts of nutrients. How this is physiologically regulated in humans has been subjected to research into interoceptive awareness of body states during fasting and food consumption. However, there is no research on the distinct effects of carbohydrate or protein intake on interoception. Therefore, we aimed to investigate the impact of fasting and consumption of standardized carbohydrate and protein shakes on interoception in a repeated-measures cross-over design in a sample of 37 healthy, normal weight males. As a physiological correlate of interoception, we measured heartbeat-evoked potentials (HEPs), which are suggested to reflect the cortical representation of cardiac signals, during eight-minutes resting state EEG-recordings. After a 16-hour fasting period, the HEP amplitudes were lower over right central and parietal electrodes and increased after ingestion of the nutritional shake. Exploratory analyses indicated that the difference between fasting and satiety was more prominent at carbohydrate compared protein testing days. Correlation analyses with heart rate variability (HRV) suggested that high cardiac sympathetic activity is related to lower HEP amplitudes. Furthermore, cardiac sympathetic activity and stress indices decreased from before to after the intervention, whereas HRV increased. Together, this study shows for the first time that fasting and the intake of a nutritional shake affects cardiac measures of autonomic nervous system functioning and the neural correlates of cardiac interoception. These findings could be relevant for diets and psychosomatic disorders, including eating disorders.

Integral pulse frequency modulation model driven by sympathovagal dynamics: Synthetic vs. real heart rate variability

Computational models that generate synthetic heart rate variability (HRV) series constitute important tools for the assessment of the effect of autonomic nervous system activity on cardiovascular control, and for the evaluation of novel algorithms using synthetic data. A widely used technique for synthetic HRV generation is the integral pulse frequency modulation (IPFM) model; however, IPFM relies on the HRV spectral paradigm, which cannot separate sympathetic and vagal oscillations that are overlapped in the low-frequency band (0.04–0.15 Hz). To overcome this limitation, a novel IPFM-inspired model driven by cardiac sympathetic and vagal dynamics estimated from HRV is proposed, where our recently developed sympathetic and parasympathetic activity indices that rely on orthonormal Laguerre expansions of the RR interval autoregressive kernels are exploited. The performance of the proposed model is evaluated by comparing the synthetic vs. real RR interval series in a simulation study involving postural changes, with real HRV data gathered from 10 healthy subjects. Moreover, the performance of the proposed model is compared with that of the standard IPFM to discern different autonomic control states associated with resting and postural changes. The results confirm that the proposed physiologically inspired model adequately predicts RR intervals during resting and postural changes. The proposed model clearly outperforms the standard IPFM method, considering both median error, and maximum error. The developed model provides valuable insights for a better understanding of the sympathovagal activity in the analysis of heartbeat dynamics.

Multisystem physiological reactivity during help-seeking for attachment needs in school-aged children: differences as a function of attachment

ABSTRACT In this study, we sought to expand on what is currently known regarding autonomic nervous system (ANS) reactivity in middle childhood as a function of attachment. ANS activity includes multiple indices – respiratory sinus arrhythmia (RSA) is an index of parasympathetic nervous system activation (PNS) and electrodermal activity (EDA) is an index of sympathetic nervous system activation (SNS). Children (N = 103) completed Child Attachment Interviews and read vignettes describing situations aimed to activate attachment needs (NEED; e.g., getting hurt, which can elicit need for comfort or assistance) and help-seeking (HS; when children experience need and seek comfort from attachment figures), while SNS and PNS reactivity were monitored. Attachment was not associated with children’s SNS or PNS reactivity during NEED, but attachment was associated with physiological reactivity during HS: Dismissing attachment was associated with greater SNS activation (higher EDA) and preoccupied attachment with PNS deactivation (lower RSA, greater vagal withdrawal) during HS.

BRAIN PERIVASCULAR MACROPHAGES CONTRIBUTE TO THE DEVELOPMENT OF HYPERTENSION THROUGH SYMPATHETIC ACTIVATION IN STROKE-PRONE SPONTANEOUSLY HYPERTENSIVE RATS

Objective: Hypertension is associated with systemic inflammation. The activation of the sympathetic nervous system is critically involved in the pathogenesis of hypertension. Brain perivascular macrophages (PVMs) can be affected by circulating inflammatory cytokines and contribute to sympathoexcitaion in a heart failure model. We thus investigated whether brain PVMs contribute to the development of hypertension through sympathoexcitation. Design and method: We measured blood pressure and evaluated the number of brain PVMs and the plasma levels of proinflammatory cytokines in stroke-prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar–Kyoto rats (WKY) at the ages of 4, 8, and 12 weeks. To determine the contribution of brain PVMs to blood pressure elevation, we intracerebroventricularly injected liposome-encapsulated clodronate, which eliminates macrophages by inducing apoptosis, or vehicle into 8-week-old SHRSP and WKY; we then assessed its effects in 10-week-old rats. We also investigated the effects of clodronate treatment on responses to the acute intravenous injection of proinflammatory cytokines in WKY. Results: SHRSP developed hypertension over 8 weeks from 4 to 12 weeks of age. The number of brain PVMs and plasma interleukin-1β levels significantly increased at the ages of 8 and 12 weeks in SHRSP compared with WKY. Clodronate treatment attenuated the increase in blood pressure in SHRSP (δmean blood pressure, 11.6 ± 3.8 mmHg vs. 23.8 ± 1.9 mmHg; clodronate vs. vehicle, n = 7, p &lt; 0.05) but not in WKY. Clodronate treatment reduced the depressor effect of hexamethonium, an index of sympathetic activity; it also reduced the neuronal activity marker c-Fos in sympathetic regulatory nuclei such as the hypothalamic paraventricular nucleus and rostral ventrolateral medulla and reduced the expression of cyclooxygenase-2 and prostaglandin E2, a downstream pathway in activated macrophages, in SHRSP but not in WKY. Furthermore, clodronate treatment attenuated the increase in blood pressure and renal sympathetic nerve activity (RSNA) in response to an acute intravenous injection of interleukin-1β in WKY (δmean blood pressure, 8.8 ± 2.5 mmHg vs. 21.2 ± 4.6 mmHg; integrated RSNA, 125.6 ± 10.4 % vs. 213.1 ± 22.2 %; clodronate vs vehicle, n = 5, p &lt; 0.05). Conclusions: Brain PVMs contribute to the development of hypertension via sympathetic activation. PVMs may be activated by increased levels of circulating interleukin-1β.

Cardiac sympathetic activity during recovery as an indicator of sympathetic activity during task performance

The goals of this research were to analyze cardiac sympathetic recovery patterns and evaluate whether sympathetic cardiac responses to a task challenge can be predicted usingresidual cardiac activity measured directly after the task (that is, during the recovery period). In two studies (total N=181), we measured cardiac sympathetic activity, quantified as pre-ejection period and RB interval, during both task performance and the 2-min recovery period following the task. Additional analyses examined effects on the RZ interval. We found that sympathetic recovery from a task was rather quick: Cardiovascular recovery occurred within the first 30s of the recovery period. Nevertheless, residual cardiac activity during the recovery period had predictive power for task-related cardiac activity. This suggests that sympathetic cardiac activity during recovery may serve as a useful indicator of task-related cardiac sympathetic activity. We discuss the implications of these findings for practical applications and the design of future studies.

RZ Interval as an Impedance Cardiography Indicator of Effort-Related Cardiac Sympathetic Activity.

Research on effort and motivation commonly assesses how the sympathetic branch of the autonomic nervous system affects the cardiovascular system. The cardiac pre-ejection period (PEP), assessed via impedance cardiography, is a common outcome, but assessing PEP requires identifying subtle points on cardiac waveforms. The present research examined the psychometric value of the RZ interval (RZ), which has recently been proposed as an indicator of sympathetic activity, for effort research. Also known as the initial systolic time interval (ISTI), RZ is the time (in ms) between the ECG R peak and the dZ/dt Z peak. Unlike PEP, RZ involves salient waveform points that are easily and reliably identified. Data from two experiments evaluated the suitability of RZ for effort paradigms and compared it to a popular automated PEP method. In Studies 1 (n = 89) and 2 (n = 71), participants completed a standard appetitive task in which each correct response earned a small amount of cash. As expected, incentives significantly affected PEP and RZ in both experiments. PEP and RZ were highly correlated (all rs ≥ 0.89), and RZ consistently yielded a larger effect size than PEP. In Study 3, a quantitative synthesis of the experiments indicated that the effect size of RZ's response to incentives (Hedges's g = 0.432 [0.310, 0.554]) was roughly 15% larger than PEP's effect size (g = 0.376 [0.256, 0.496]). RZ thus appears promising for future research on sympathetic aspects of effort-related cardiac activity.

Relationship between truck driver fatigue and rear-end collision risk.

The fatigue of truck, bus, and taxi drivers has been a causal trigger for road accidents. However, the relationship between collision risk and the extent of objective fatigue has yet to be confirmed. In this study, we aimed to identify the relationship between autonomic nerve function as an objective parameter of fatigue and the extent of rear-end collision risk, which includes not only objectively risky events but also situations in which truck drivers require safety guidance from safety transport managers. Data of 33 truck driver participants (2 females, 31 males, 46.0 ± 9.1 years old, min–max: 24–65 years old) were analyzed. Drive recorder and automotive sensor data were collected over an eight-month period, and the autonomic nerve function during resting state in drivers was evaluated daily, pre- and post-shift, using pulse waves and electrocardiographic waveform measurement. The rear-end collision risk Index was developed using decision tree analysis of the audiovisual drive recorder data and distance data from the front automotive sensors. The rear-end collision risk index of shift-day was positively correlated with the sympathetic nerve activity index of post-shift condition on the previous day. This suggests that fatigue-related sympathetic nerve overactivity of post-shift condition increases the rear-end collision risk in the following day. Measures, such as actively seeking rest and undertaking fatigue recovery according to the degree of sympathetic nerve activity of post-shift condition, are necessary in order to prevent truck drivers’ rear-end collisions.