Suppression Of Heart Rate Variability Research Articles

Menstrual cycle, heart rate variability (HRV), and mood: Is cyclicity of HRV associated with cyclicity of mood symptoms?

In an effort to understand potential biological indices of menstrually-related mood changes experienced by some naturally cycling individuals, we previously investigated whether vagally-mediated HRV (i.e., a biomarker of physical and mental health) fluctuates across the menstrual cycle. Our recent meta-analysis revealed a significant decrease of HRV in the midluteal phase which, as two-follow up studies suggest, is correlated with progesterone. However, the question remains whether cyclicity of HRV is associated with cyclicity of mood symptoms. Fifty naturally-cycling participants (M=24.8 years, SD=5.8) were examined (10-min baseline EKG for HRV assessment, PANAS for mood assessment) in three precisely determined cycle phases (ovulatory, midluteal, menstrual) via ovulation testing. To test the idea that degree of midluteal (vs. menstrual phase) HRV suppression is associated with the degree of PANAS same-day mood deterioration in the midluteal phase (vs. menstrual phase), each person’s difference score in HRV between the two phases was assessed. This between-person factor was taken into multilevel models predicting PANAS items from menstrual cycle phase. Analyses revealed that greater midluteal phase suppression of HRV was associated with greater midluteal phase increases in distress, as well as several fear and anxiety variables. No differences in sadness or irritability were found. These findings suggest that cyclical HRV suppression and cyclical increase in mood symptoms tend to covary. Further work is needed to clarify whether cyclicity of HRV may serve as a biological index of menstrually-related mood disorders.

Structural and functional changes of the heart and electrical disorders in patients with coronary artery disease with concomitant anemia

The aim of the study: to investigate the effect of concomitant anemia on the features of cardiac remodeling and electrical disorders in patients with coronary artery disease (CAD). Materials and methods. In total, 89 patients with CAD, stable angina II–III FC were examined (men – 34, women – 55, age – 69 (61; 72) years). All patients were divided into 2 groups: the main group (n = 44) consisted of patients with CAD and anemia, the comparison group (n = 45) – patients with CAD without iron-deficiency anemia. The results of echocardioscopy and 24-hour ECG (Holter) monitoring were analyzed. Results. Left ventricular (LV) end-diastolic and end-systolic volume were higher in the main group by 24.7 % (U = 60.0; P < 0.05) and 25.9 % (U = 53.5, P < 0.05), respectively; end-diastolic and end-systolic left ventricular index also were higher in the main group by 20.2 % (U = 99.5; P < 0.05) and 34.8 % (U = 98.5; P < 0.05), respectively. There was no statistically significant difference in the types of LV geometry; however, the left ventricular mass index was significantly higher by 12.0 % in patients of the main group (U = 315.5; P < 0.05). The patients of both groups mostly showed diastolic dysfunction type 1, however, in the main group, there was a tendency to increase the number of patients with diastolic dysfunction type 2 and type 3. In patients of the main group, in the active period, there was a decrease in SDNNi by 31.85 % (U = 216; P < 0.05), VLF by 53.79 % (U = 176; P < 0.05); increase in LF by 60.56 % (U = 53; P < 0.05) and SI by 2.14 times (U = 43.5; P < 0.05). The presence of anemia in patients with CAD caused a twofold increase in the risk of autonomic dysfunction (BP = 2.045; 95 % CI 1.084–3.861; P < 0.05), 1.5 times increase in tachycardia episodes (BP = 1.510; 95 % CI 1.047–2.178; P < 0.05) and 2.2 times increase in myocardial ischemia (BP = 2.173; 95 % CI 1.047–4.512; P < 0.05). Conclusions. Concomitant anemia in patients with coronary artery disease adversely affects the structural and geometric properties of the heart, leads to an overall suppression of heart rate variability, increases the sympathetic tone of the autonomic nervous system in daytime period and the stress index, as well as raises the risk of autonomic dysfunction, tachycardia and myocardial ischemia.

Early neonatal heart rate variability patterns in different subtypes of perinatal hypoxic-ischemic brain injury.

This study aims to compare the longitudinal changes in heartrate variability (HRV) during therapeutic hypothermia in neonates with different subtypes of hypoxic-ischemic brain injury. HRV was computed from 1 hour time-epochs q6 hours for the first 48 hours. Primary outcome was brain-injury pattern on MRI at 4(3-5) days. We fitted linear mixed-effect regression models with HRV metric, brain injury subtype and postnatal age. Among 89 term neonates, 40 neonates had abnormal brain MRI (focal infarct 15 (38%), basal-ganglia predominant 8 (20%), watershed-predominant 5 (13%), and mixed pattern 12 (30%)). There was no significant difference in the HRV metrics between neonates with normal MRI, focal infarcts and basal ganglia pattern. At any given postnatal age, the degree of HRV suppression(HRV measure in the brain-injury subtype group/HRV measure in Normal MRI group) was significant in neonates with watershed pattern (SDNN(0.63, p = 0.08), RMSSD(0.74, p = 0.04)) and mixed pattern injury (SDNN (0.64, p < 0.001), RMSSD (0.75, p = 0.02)). HRV suppression was most profound at the postnatal age of 24-30 h in all brain injury subtypes. Neonates with underlying watershed injury with or without basal-ganglia injury demonstrates significant HRV suppression during first 48 hour of hypothermia therapy. Our study suggests that suppression of heartrate variability in neonates during therapeutic hypothermia varies according to the pattern of underlying hypoxic-ischemic brain injury. Neonates with watershed predominant pattern and mixed pattern of brain injury have the most severe suppression of heartrate variability measures. Heartrate variability monitoring may provide early insights into the pattern of hypoxic-ischemic brain injury in neonates undergoing therapeutic hypothermia earlier than routine clinical MRI.

Exploring autonomic regulation in children with ADHD with and without comorbid anxiety disorder through three systematic levels of cardiac vagal control analysis: Rest, reactivity, and recovery.

Autonomic nervous system (ANS) dysregulation, characterized by reduced vagally mediated Heart Rate Variability (HRV), has been associated with Attention-Deficit/ Hyperactivity Disorder (ADHD). This study investigated the dynamic vagal modulation of cardiac output in response to shifts in environmental demands in children and adolescents with ADHD, with and without a comorbid anxiety disorder. High-frequency HRV (HF-HRV) measures were obtained from 46 children and adolescents ranging from 6 to 17 (M=9.38; SD = 2.31) years old, during three successive experimental conditions: a baseline recording followed by a sustained attention task, and a post-task recovery period. Findings support the reliability of the d2 Test, a cancelation test of attention and concentration, to induce parasympathetic withdrawal and extend prior work on "vagal flexibility". Further, these findings suggest a pattern of group differences in ANS functioning in children with ADHD, with and without a comorbid anxiety disorder. Only the ADHD without comorbid anxiety group showed a normative autonomic response to the cognitive challenge (reduced HF-HRV). The participants did not display an adaptive process of restoration following the cognitive challenge; the HRV suppression was prolonged during post-task recovery period, suggesting that ANS responded as if the cognitive stressor was still present. The current paper covers and discusses theoretical implications for the abnormalities in neurophysiological functioning and the different physiological responses in the two ADHD subtypes.

Social-Pragmatic Inferencing, Visual Social Attention and Physiological Reactivity to Complex Social Scenes in Autistic Young Adults

This study examined social-pragmatic inferencing, visual social attention and physiological reactivity to complex social scenes. Participants were autistic young adults (n = 14) and a control group of young adults (n = 14) without intellectual disability. Results indicate between-group differences in social-pragmatic inferencing, moment-level social attention and heart rate variability (HRV) reactivity. A key finding suggests associations between increased moment-level social attention to facial emotion expressions, better social-pragmatic inferencing and greater HRV suppression in autistic young adults. Supporting previous research, better social-pragmatic inferencing was found associated with less autistic traits.

Snacking on Whole Almonds for Six Weeks Increases Heart Rate Variability during Mental Stress in Healthy Adults: A Randomized Controlled Trial.

Cardiac autonomic regulation can be indirectly measured by heart rate variability (HRV). Low HRV, which can be induced by mental stress, is a predictor of risk of sudden cardiac death. Few studies have investigated cause-and-effect relationships between diet and HRV. Nut consumption is associated with CVD risk reduction, but the impact on HRV, particularly in response to stress, is unclear. Men and women (30–70 y) with above average risk of developing CVD were randomly assigned in a 6-week randomized, controlled, parallel arm trial to consume either whole almond or isocaloric control snacks (20% of daily estimated energy requirement). Control snacks contained the average nutrient profile of UK snacks. Five-minute periods of supine heart rate (HR) and HRV were measured at resting and during mental stress (Stroop color-word test) at baseline and six weeks. High frequency (HF) power, which reflects parasympathetic regulation of HR, was increased following almonds during the mental stress task relative to control (mean difference between groups 124 ms2; 95% CI 11, 237; p = 0.031, n = 105), but other indices were unaffected. Snacking on whole almonds instead of typical snacks may reduce risk of CVD partly by ameliorating the suppression of HRV during periods of mental stress.

Getting to the Heart of Low Sensitivity to Alcohol: Context Moderates Low Cardiovascular Response to Alcohol in Persons With a Family History of Alcohol Use Disorder.

BackgroundLow sensitivity to alcohol in persons with a family history of alcoholism (FH+), compared to those without (FH−), contributes to risk for alcohol use disorder (AUD). However, sensitivity of FH+ cardiovascular response to alcohol is not well understood. This gap is significant because cardiovascular processes contribute to emotional regulation and stress response problems theorized to be central to the development and persistence of AUD. This study compared changes in heart rate (HR) and HR variability (HRV) between FH groups after consuming alcohol and control beverages and examined how these changes were moderated by emotional and alcohol‐related contexts.MethodsYoung adults (N = 165) with FH+ (n = 110) or FH− (n = 55) each completed 2 sessions, separated by 1 week. They received one of 3 different beverages (alcohol, placebo, and told‐no‐alcohol) in each session. Electrocardiogram data were recorded during pre–beverage consumption and post–beverage consumption baselines, and then during 4 picture cue tasks (neutral, positive, negative, and alcohol‐related). Generalized estimating equations were used to examine differences in cardiovascular reactivity (changes in HR and HRV power at ~ 0.1 Hz) across FH groups, beverage conditions, and picture cue tasks.ResultsA significant beverage condition × cue task × FH interaction effect on HRV was observed. The FH+ group, compared to the FH− group, showed (a) significantly less HRV suppression in specific cue contexts following alcohol, (b) a mixed pattern of more and less HRV suppression across cue contexts following placebo, and (c) a similar HRV reactivity pattern in the told‐no‐alcohol condition across cue tasks. For HR, there were no significant effects involving FH.ConclusionsDiminished cardiovascular sensitivity to oral alcohol in FH+ persons varied within a given drinking episode depending on emotional and alcohol‐related features of the context, suggesting that environmental characteristics play a role in the expression of low sensitivity to alcohol among FH+ individuals.

Indicators of the relationship between heart rate variability and levels of glycemia and cholesterol in vibration pathology

Introduction. Vibration disease (VD) is one of the leaders in the structure of occupational diseases among workers in the coal mining industry. The occurrence of disorders at the systemic level (primarily in the nervous and vascular systems) leads to suppression of heart rate variability (HRV) in vibration pathology as a result of damage to vegetative fi bers, centers, ganglia. The study of metabolic disorders in relation to HRV indicators, including nonlinear ones, is of interest for understanding the mechanisms of the VD, and is also important for fi nding non-invasive and less expensive methods of dynamic control.The aim of the studywas to study the parameters of heart rate variability, total cholesterol and blood glucose levels in patients with vibration disease, to identify the relationship between them.Materials and methods. 75 patients of the Clinic of the Research Institute for Complex Problems of Hygiene and Occupational Diseases subjected to industrial vibration for 10 years or more (the main group) and 20 people of the control group who never had contact with industrial vibration were examined. Th e age of the subjects was 40–60 years. Fasting blood glucose and total cholesterol levels were studied, heart rate variability was studied. Frequency and nonlinear phenomena of heart rate variability were analyzed. Spearman correlation coeffi cient was determined to assess the strength of the relationship between blood and heart rate variability.Results. Glucose and cholesterol levels were statistically higher in the group of patients with vibration disease. Spectral parameters of high — and low-frequency heart rate variability in the main group signifi cantly decreased. In patients with vibration pathology of the approximated entropy was signifi cantly lower, whereas deranty fl uctuation analysis increased. Th ese changes of heart rate variability indicate the involvement of all departments of vegetative nervous system, the development of relative sympathicotonia. Correlations of average strength between heart rate variability and levels of glycemia and cholesterol were revealed.Conclusion.Under the infl uence of industrial vibration in workers’ blood cholesterol and glucose levels increase, heart rate variability is suppressed and correlated with an increase in metabolic disorders.

Evolving changes in fetal heart rate variability and brain injury after hypoxia-ischaemia in preterm fetal sheep.

Fetal heart rate variability is a critical index of fetal wellbeing. Suppression of heart rate variability may provide prognostic information on the risk of hypoxic-ischaemic brain injury after birth. In the present study, we report the evolution of fetal heart rate variability after both mild and severe hypoxia-ischaemia. Both mild and severe hypoxia-ischaemia were associated with an initial, brief suppression of multiple measures of heart rate variability. This was followed by normal or increased levels of heart rate variability during the latent phase of injury. Severe hypoxia-ischaemia was subsequently associated with the prolonged suppression of measures of heart rate variability during the secondary phase of injury, which is the period of time when brain injury is no longer treatable. These findings suggest that a biphasic pattern of heart rate variability may be an early marker of brain injury when treatment or intervention is probably most effective. Hypoxia-ischaemia (HI) is a major contributor to preterm brain injury, although there are currently no reliable biomarkers for identifying infants who are at risk. We tested the hypothesis that fetal heart rate (FHR) and FHR variability (FHRV) would identify evolving brain injury after HI. Fetal sheep at 0.7 of gestation were subjected to either 15 (n=10) or 25min (n=17) of complete umbilical cord occlusion or sham occlusion (n=12). FHR and four measures of FHRV [short-term variation, long-term variation, standard deviation of normal to normal R-R intervals (SDNN), root mean square of successive differences) were assessed until 72h after HI. All measures of FHRV were suppressed for the first 3-4h in the 15min group and 1-2h in the 25min group. Measures of FHRV recovered to control levels by 4h in the 15min group, whereas the 25min group showed tachycardia and an increase in short-term variation and SDNN from 4 to 6h after occlusion. The measures of FHRV then progressively declined in the 25min group and became profoundly suppressed from 18 to 48h. A partial recovery of FHRV measures towards control levels was observed in the 25min group from 49 to 72h. These findings illustrate the complex regulation of FHRV after both mild and severe HI and suggest that the longitudinal analysis of FHR and FHRV after HI may be able to help determine the timing and severity of preterm HI.

Surgery at Sea: The Effect of Simulated High Sea States on Surgical Performance.

The US Navy initiated design concepts for a Medical Mission Module Support Container (M3SC), a mobile operating room capable of rapid installation aboard maneuverable ships within proximity of active combat units. The M3SC provides an alternative echelon of care in the current trauma system by decreasing the time between point of injury, arrival, and surgical intervention. The mobile ships used as M3SC platforms, however, are more susceptible to oceanic conditions that can induce detrimental physiologic motion sickness in medical personnel and patients aboard the vessels. This study investigated the effects of different sea-state motion conditions on the performance of surgical teams. Six four-person surgical teams performed 144 procedures in an M3SC aboard a Stewart motion table that simulated motion profiles of sea states 0, 3, and 4. A modified human-worn partial- task surgical simulator was used as a surgical surrogate to simulate the four most common, wartime, improvised explosive device injuries in the past 10 years. Electroencephalographs and heart rate variability (HRV) data were collected from surgeons and surgical technologists during each procedure to assess real-time physiologic responses to motion. Two postprocedure surveys, a Surgical Task Load Index and a Motion Sickness Assessment Questionnaire, were given to assess subjective responses of workload stress and motion-induced kinetosis. Surgical subject matter experts quantified surgical performance after each procedure by measuring blood loss and orthopedic pin placement to evaluate each intervention. Motion did not significantly influence overall performance (ρ = .002). Surgical procedure was the strongest predictor of performance. HRV was used to measure stress and was increased in surgical technologists; however, HRV was decreased for surgeons and technologists in motion. There was a significant interaction between role and motion (ρ = .002): Surgeons had higher workloads than did surgical technologists and neither demonstrated differences between motion and no motion. Surgeons demonstrated significantly decreased workloads under motion conditions (ρ = 0.002); however, surgeons perceived their workload to be higher. We attribute this to their increased critical thinking and physical execution of procedures. Surgeons and surgical technologists showed a trend toward HRV suppression within the motion conditions. This may indicate a coping response to the increased stress of the motion setting. Procedure and team dynamic were the strongest predictors of overall performance, suggesting a learning curve exists and that added focus on training should be enforced. Based on data collected in this study, similar surgical procedures should be implemented aboard these classes of ships. By doing so, injured military personnel would have more timely access to care. Surgical team members were aware of craft motion, used compensatory measures, and exhibited some physiological response.

Pattern of brain injury and depressed heart rate variability in newborns with hypoxic ischemic encephalopathy.

BackgroundDecreased heart rate variability (HRV) is a measure of autonomic dysfunction and brain injury in newborns with hypoxic ischemic encephalopathy (HIE). This study aimed to characterize the relationship between HRV and brain injury pattern by MRI in newborns with HIE undergoing therapeutic hypothermia.MethodsHRV metrics were quantified in the time domain (αS, αL, and root mean square at short [RMSS] and long [RMSL] time scales) and frequency domain (relative low-[LF] and high-frequency [HF] power) during the time period 24–27 hours of life. Brain injury pattern by MRI was classified as no injury, pure cortical/white matter injury, mixed watershed/mild basal nuclei injury, predominant basal nuclei or global injury, and died. HRV metrics were compared across brain injury pattern groups using a random effects mixed model.ResultsData from 74 infants were analyzed. Brain injury pattern was significantly associated with degree of HRV suppression. Specifically, negative associations were observed between pattern of brain injury and RMSS (estimate −0.224, SE 0.082, p=0.006), RMSL (estimate −0.189, SE 0.082, p=0.021), and LF power (estimate −0.044, SE 0.016, p=0.006).ConclusionDegree of HRV depression is related to pattern of brain injury. HRV monitoring may provide insights into pattern of brain injury at the bedside.

Transdermal neuromodulation of noradrenergic activity suppresses psychophysiological and biochemical stress responses in humans.

We engineered a transdermal neuromodulation approach that targets peripheral (cranial and spinal) nerves and utilizes their afferent pathways as signaling conduits to influence brain function. We investigated the effects of this transdermal electrical neurosignaling (TEN) method on sympathetic physiology under different experimental conditions. The TEN method involved delivering high-frequency pulsed electrical currents to ophthalmic and maxillary divisions of the right trigeminal nerve and cervical spinal nerve afferents. Under resting conditions, TEN significantly suppressed basal sympathetic tone compared to sham as indicated by functional infrared thermography of facial temperatures. In a different experiment, subjects treated with TEN reported significantly lower levels of tension and anxiety on the Profile of Mood States scale compared to sham. In a third experiment when subjects were experimentally stressed TEN produced a significant suppression of heart rate variability, galvanic skin conductance, and salivary α-amylase levels compared to sham. Collectively these observations demonstrate TEN can dampen basal sympathetic tone and attenuate sympathetic activity in response to acute stress induction. Our physiological and biochemical observations are consistent with the hypothesis that TEN modulates noradrenergic signaling to suppress sympathetic activity. We conclude that dampening sympathetic activity in such a manner represents a promising approach to managing daily stress.

Who benefits from simulator training: Personality and heart rate variability in relation to situation awareness during navigation training

ObjectiveThis study tested the relationship between individual differences and Situation Awareness (SA) during training in a navigation simulator. BackgroundSimulators have become an important tool in the training and education of maritime personnel with a view to improving decisions and performance. There are a few, inconclusive empirical studies that have focused on mapping personality characteristics and their link to the ability to generate and maintain SA during simulator training. MethodThirty-six first-year students from the Royal Norwegian Navy Officer Candidate School participated in the study. SA was measured using both subjective and observer ratings. ResultsThe results indicated that low scores on Neuroticism and high scores on Extraversion and Conscientiousness (resilient personality type) predicted both subjective and observer-rated SA. Furthermore, participants with high SA were able to modulate their Heart Rate Variability (HRV), with suppression of HRV during navigation training as well showing recovery of HRV. ApplicationThe potential applications of this research include the assessment of personality differences as a tool in selecting navigators, and the use of HRV as an objective index of adaptability to environmental demands.

Genetic Strain Differences in Learned Fear Inhibition Associated with Variation in Neuroendocrine, Autonomic, and Amygdala Dendritic Phenotypes

Mood and anxiety disorders develop in some but not all individuals following exposure to stress and psychological trauma. However, the factors underlying individual differences in risk and resilience for these disorders, including genetic variation, remain to be determined. Isogenic inbred mouse strains provide a valuable approach to elucidating these factors. Here, we performed a comprehensive examination of the extinction-impaired 129S1/SvImJ (S1) inbred mouse strain for multiple behavioral, autonomic, neuroendocrine, and corticolimbic neuronal morphology phenotypes. We found that S1 exhibited fear overgeneralization to ambiguous contexts and cues, impaired context extinction and impaired safety learning, relative to the (good-extinguishing) C57BL/6J (B6) strain. Fear overgeneralization and impaired extinction was rescued by treatment with the front-line anxiety medication fluoxetine. Telemetric measurement of electrocardiogram signals demonstrated autonomic disturbances in S1 including poor recovery of fear-induced suppression of heart rate variability. S1 with a history of chronic restraint stress displayed an attenuated corticosterone (CORT) response to a novel, swim stressor. Conversely, previously stress-naive S1 showed exaggerated CORT responses to acute restraint stress or extinction training, insensitivity to dexamethasone challenge, and reduced hippocampal CA3 glucocorticoid receptor mRNA, suggesting downregulation of negative feedback control of the hypothalamic-pituitary-adrenal axis. Analysis of neuronal morphology in key neural nodes within the fear and extinction circuit revealed enlarged dendritic arbors in basolateral amygdala neurons in S1, but normal infralimbic cortex and prelimbic cortex dendritic arborization. Collectively, these data provide convergent support for the utility of the S1 strain as a tractable model for elucidating the neural, molecular and genetic basis of persistent, excessive fear.

Effects of a peripheral cholinesterase inhibitor on cytokine production and autonomic nervous activity in a rat model of sepsis

Purpose Recently, cholinergic anti-inflammatory pathway manipulation has been proposed as a new strategy to control cytokine production in sepsis. We investigated whether hypercytokinemia can be controlled via this pathway in an animal model of sepsis, with concomitant monitoring of autonomic nervous activity involving heart rate variability (HRV) analysis of electrocardiographic R-R intervals. Methods Sixty-eight adult male Sprague–Dawley rats were used (28 for examination of cytokine production and autonomic nervous activity; 40 for survival analysis). Each part of the study involved four animal groups, including two control groups without drug administration. Sepsis was induced by cecal ligation and puncture (CLP). Distigmine bromide, a peripheral, non-selective cholinesterase inhibitor (0.01 mg/kg), was administered subcutaneously 90 min after surgery. Continuous electrocardiograms were recorded for 5 min before and after surgery (at intervals of 5 h) in CLP and sham-operated animals for HRV analysis. Blood samples were collected 20 h after surgery for serum cytokine and catecholamine assay. Results On HRV analysis, distigmine inhibited reduction of total power and high-frequency components in CLP animals ( P < 0.05). Distigmine significantly inhibited cytokine induction (IL-6 and IL-10) ( P < 0.01) as well as increase in serum levels of noradrenaline and dopamine ( P < 0.05). Distigmine did not significantly improve CLP animal survival rate. Conclusions The cholinesterase inhibitor distigmine inhibited induction of inflammatory cytokines and catecholamines as well as HRV suppression in a rat CLP model, suggesting that an agent modulating the cholinergic anti-inflammatory pathway can control excess cytokine production involved in the pathogenesis of severe sepsis/septic shock.

The Relationship Between Aversive Conditioning and Risk-avoidance in Gambling

This study investigated the relationship between aversive conditioning, heart rate variability suppression, behavioral activation system/behavioral inhibition system and risk-avoidance on the Iowa gambling task (IGT) in a nonclinical sample (29 male, 29 female, mean age = 20.7). A laboratory based Pavlovian aversive conditioning paradigm was used where a 1500 Hz tone (CS+) was followed by a burst of loud white noise (US), and a 850 Hz (CS-) tone was never followed by the US. In a subsequent extinction phase where the CS+ and CS- were presented without the US, conditioned skin conductance responses to the CS+ indicated aversive conditioning. The results showed that the participants who did not show aversive conditioning (N = 26) exhibited significantly less risk-avoidance compared to participants who did show aversive conditioning (N = 32). Regression analysis showed that among the study variables, only aversive conditioning contributed significantly to explaining variance in risk-avoidance. These results may have implications for understanding risk-taking in gambling in general, and may be a starting point understanding the role of aversive conditioning in the development and maintenance of gambling problems.

The Effect of Brief Situational Awareness Training in a Police Shooting Simulator: An Experimental Study

The aim of this study was to investigate the effect of situational awareness (SA) training in a shooting simulator. Forty 1st-year students from the Norwegian Police University College participated in this study. They were divided into 2 groups and matched with respect to sex and previous weapon experience. The SA-trained group received scenario-based training with freeze technique and reflection based on the SA stages, whereas the control group received skill training. During the test phase SA was measured both subjectively and objectively and performance was measured by the number of shots fired and number of hits. The results showed that both subjective and observer ratings reported the SA-trained group to have higher SA. This was also true for performance, and the SA-trained group showed less mental workload measured as suppression of heart rate variability during the execution of the mission. These results indicate that brief SA-specific training in a shoot–not shoot simulator can improve police cadets' SA in critical situations.

Vagal influence on working memory and attention

The aim of the present study was to investigate the effect of vagal tone on performance during executive and non-executive tasks, using a working memory and a sustained attention test. Reactivity to cognitive tasks was also investigated using heart rate (HR) and heart rate variability (HRV). Fifty-three male sailors from the Royal Norwegian Navy participated in this study. Inter-beat-intervals were recorded continuously for 5 min of baseline, followed by randomized presentation of a working memory test (WMT) based on Baddeley and Hitch's research (1974) and a continuous performance test (CPT). The session ended with a 5-min recovery period. High HRV and low HRV groups were formed based on a median split of the root mean squared successive differences during baseline. The results showed that the high HRV group showed more correct responses than the low HRV group on the WMT. Furthermore, the high HRV group showed faster mean reaction time (mRT), more correct responses and less error, than the low HRV group on the CPT. Follow-up analysis revealed that this was evident only for components of the CPT where executive functions were involved. The analyses of reactivity showed a suppression of HRV and an increase in HR during presentation of cognitive tasks compared to recovery. This was evident for both groups. The present results indicated that high HRV was associated with better performance on tasks involving executive function.

Heart rate control of blood pressure variability in children: a study in subjects with fixed ventricular pacemaker rhythm

1. To investigate the influence of heart rate variability on blood pressure variability, short-term variability in heart rate and blood pressure was studied in 10 children with fixed ventricular pacemaker rhythm (80 beats/min). Ten healthy children, in sinus rhythm, served as a reference population. 2. Arterial blood pressure and heart rate were measured continuously using a finger arterial device and an ECG respectively. Power spectra for heart rate and blood pressure (systolic and diastolic) were calculated in both supine and orthostatic positions. In addition, acute changes in blood pressure and heart rate during active standing were studied. 3. Healthy children exhibited considerable heart rate variability, which was slightly more pronounced in the supine position, while children with a fixed ventricular rate had no heart rate variability in either position. 4. Despite the differences in heart rate variability, mean systolic blood pressure and its variability profiles were poorly affected by the suppression of heart rate variability. The lack of autonomic control on the sinus node was associated with a reduction in magnitude of the changes in systolic blood pressure variability induced by orthostatic posture. 5. The suppression of heart rate fluctuations induced a noticeable decrease in diastolic blood pressure fluctuations, which was most conspicuous in the children with fixed cardiac rhythm when in the supine position. This may be explained by the lack of diastolic blood pressure fluctuations, physiologically due to heart rate fluctuations through the run-off effect: the longer the cardiac cycle, the greater the diastolic pressure decay. These results may challenge the classical theory of baroreflex-mediated diastolic blood pressure control described in adult patients. 6. During active standing, the early drop in systolic blood pressure was greater in subjects with fixed ventricular rhythm. A rise in heart rate of 36 beats/min was observed in the healthy subjects in response to active standing. 7. We conclude that in normal children, heart rate fluctuations increase the blood pressure variability rather than buffering it. However, during acute orthostatic stress, the abrupt baroreflex-mediated heart rate rise may partly compensate for the reduction in blood pressure.

Relations among memory performance, mental workload and cardiovascular responses

The levels of processing paradigm has been a powerful research framework in the study of memory for close to a quarter century. However, an objective index of depth of processing is still lacking. Two experiments using lists of words, presented to male subjects, were performed to compare the effects of depth of processing, rate of presentation, and task incentive on recognition memory performance, self-reported workload, and cardiovascular responding. Memory performance results from the two experiments demonstrated higher recognition levels associated with deeper processing and slower presentation rates. Deeply encoded items were associated with faster recognition latencies. Self-reported workload levels were higher for deeper processing and faster presentation rates. Cardiovascular responses were generally amplified with the addition of a task incentive. Increased blood pressure was associated with faster presentation rates. Increased heart rate and decreased T-wave amplitude (i.e., increased sympathetic activity) were uniquely associated with the deep encoding of information presented at the fastest rate. This particular encoding condition was associated with increased recognition levels. Deeply encoded items were associated with increased suppression of heart rate variability during recognition. This combination of behavioral and cardiovascular measures may provide the basis for an objective index of depth of processing.