Heart period variability during estrogen exposure and withdrawal in female rats

Heart period, heart period variability, and an estimate of vagal tone were evaluated during estrogen exposure and withdrawal in ovariectomized, freely moving female rats. Spectral analysis was used to quantify the respiratory component of heart period variability (V?), which has been found to be sensitive to alterations of vagal tone to the heart. During estrogen withdrawal, V? decreased significantly and was accompanied by a decrease in heart period. There were no significant differences in heart period or V? between the experimental (estrogen) group and the control (no estrogen) group during estrogen exposure. Total heart period variability did not differ significantly from controls during estrogen withdrawal but it did exhibit an increase during estrogen exposure. In this experiment V? appeared to be more sensitive to changes in estrogen levels than total heart period variability. These data suggest that decreases in cardiac vagal tone and heart rate occur during estrogen withdrawal.     

Cardiac and Metabolic Responses to “Space Invaders”: An Instance of Metabolically-Exaggerated Cardiac Adjustment?

Heart rate, plus various ventilatory and metabolic indices, were monitored while 24 male subjects played a computer game of the “space invaders” type and during a control condition, in which analogous but ineffective actions were requested and the game proceeded automatically. Relative to baseline, subjects showed much larger increases in heart rate during “space invaders” than during the control condition. However, oxygen consumption, carbon dioxide production, respiratory rate and volume also increased more. While the absolute magnitude of metabolic differences between conditions could be regarded as modest relative to heart rate differences, given the effective range of variations possible for each parameter, the existence of highly significant differences in oxygen consumption and carbon dioxide production militates against assertions of overall cardiac-metabolic independence during “space invaders.” Nevertheless, analysis of individual differences in heart rate reactivity would seem to provide some evidence of metabolically-unjustified heart rate changes during “space invaders.” High heart rate reactors during “space invaders” did not differ from low reactors in either oxygen consumption or carbon dioxide production. In addition, this relatively high heart rate reactivity was specific to the “space invaders” condition; high and low heart rate reactors displayed no differences in heart rate, or in any other physiological measure, during the control condition or during baseline.     

Voluntary Control and Reactivity of Human Heart Rate

Factors in human voluntary heart rate control with and without external feedback were studied. Average voluntary heart rate control in the laboratory was comparable to the range of heart rates obtained during accelerative-decelerative ‘reactivity’ tasks in the laboratory and to heart rates obtained during various situation* outside of the laboratory. However, cardiac rate reactivity did not reliably predict voluntary control performance across subjects (Ss). With full instructions, Ss were able to increase but not decrease heart rate relative to resting levels before feedback was provided. With full-scale meter feedback. Ss could both increase and decrease heart rate relative to resting levels. Performance in Bidirectional control during feedback remained constant. The ability both to increase and to decrease heart rate transferred to the postfeedback. no-meter condition. Reversing the meaning of the Up and Down cue lights during post-feedback for half of the As had no deleterious effect on bidirectional heart rate control. The importance of physiological and situational constraints in Bidirectional heart rate control is discussed.     

Cognitive and Somatic Events Associated With Discriminative Changes in Heart Rate

In Experiment 1, 23 males were given instructions to think about anxiety-provoking cognitive events (n= 12) or relaxing cognitive events (n= 11) during 20 30-sec training trials. Significant pretrial-to-trial increases in heart rate were noted during anxiety instructions and significant pretrial-to-trial decreases in heart rate were detected during relaxation instructions. In Experiment 2,39 males were again given instructions to think about anxiety-provoking events (n= 19) or relaxing events (n= 20) during 20 30-sec training trials. In addition, half of the subjects in each of these instructional conditions were given digital heart rate feedback consistent with their instructions (e.g., were reinforced for heart rate increases during anxiety instructions), whereas half of the subjects in each instructional condition were given feedback inconsistent with their instructions (e.g., were reinforced for heart rate decreases during anxiety instructions). As in Experiment 1, significant pretrial-to-trial increases in heart rate occurred during anxiety instructions and significant pretrial-to-trial decreases in heart rate were noted during relaxation instructions. The type of feedback which subjects received had no effect on the heart rate changes. The heart rate changes in both experiments were generally accompanied by parallel changes in respiratory rate but not by changes in chin muscle tension. It appears that cognitive events can produce increases and decreases in heart rate which are comparable in magnitude to those noted during biofeedback.     

Heart Rate Biofeedback and Cold Pressor Pain

This study addressed the relative contributions of self-regulated heart rate change and belief that heart rate is changing in an instructed direction to the perception of cold pressor pain. Forty male volunteers were each assigned to one of four combinations of increase or decrease heart rate instructions and increase or decrease feedback conditions. Subjects were given an initial 45-sec cold pressor test, 25 feedback trials, and a final cold pressor in which they were told to change their heart rate in the instructed direction, but without the aid of feedback. Subjects were instructed specifically that increased heart rate was associated with increased pain and decreased heart rate with decreased pain. The veridical groups (consistent instructions and feedback) showed appropriate heart rate changes during biofeedback training and parallel changes in heart rate and pain perception during the final cold pressor. The non-veridical (reverse) feedback groups showed no heart rate change during biofeedback training and no relationship between heart rate and pain perception changes during the final cold pressor test. EMG, respiration, and skin conductance data are presented, and several mechanisms are proposed to explain the physiological and subjective changes.     

Instructed heart rate control in a high heart rate population

Forty college students were selected from a large number of introductory psychology students on the basis of high heart rate during an initial screening session. Subjects were then contacted and participated in two additional sessions during which heart rate, respiration rate, and skin conductance measures were obtained. Each session consisted of a baseline period followed by five trial periods during which subjects attempted to control their heart rate or performed a visual tracking task. Subjects were randomly assigned to one of four groups. One group served as a control and monitored a visual feedback display driven by their own heart rate but received no instructions to decrease their heart rate. In contrast, the three heart rate control groups were instructed to decrease heart rate during the trial periods by utilizing a relaxation procedure, proportional biofeedback, or proportional biofeedback plus criterion information. No group differences were present during the baseline periods. During feedback trials, however, all the training groups differed from the control in heart rate but did not differ from each other. It is suggested that feedback displays may not facilitate heart rate reduction beyond the level achieved by instructing subjects to use a general relaxation procedure.     

Decelerative changes in heart rate are associated with performance on tasks that assess intelligence

Changes in heart rate, chin electromyographic (EMG) activity, and respiration rate were monitored during the performance of three tasks that are commonly employed to assess intelligence in human adults. Stimuli from the digit span subtest (Expt. 1) of the Wechsler scales of intelligence, the picture completion subtest (Expt. 2), and the picture arrangement subtest (Expt. 3) were employed. A 10-s warning preceding the onset of each stimulus was also used in each of the experiments. During all three tasks there was an initial increase in heart rate during the first 3-4 s of the warning signal, followed by a decrease in heart rate during the last 5-6 s of the warning signal. Mean heart rate during the 5 s immediately preceding the presentation of stimuli to which subjects gave correct responses was significantly lower than mean heart rate during the 5 s immediately preceding the presentation of stimuli to which subjects gave incorrect responses. In addition, mean heart rate during the 5 s immediately preceding the presentation of stimuli to which subjects gave correct responses decreased significantly below the pre-warning baseline level, whereas mean heart rate during the 5 s preceding the presentation of stimuli to which subjects gave incorrect responses did not decrease below the baseline level. The differential heart rate results for correct and incorrect responses were consistent across the three tasks. No significant changes in chin EMG and respiration rate were noted during any of the tasks. Relationships among heart rate, attention to environmental information, and the role of attention in measures of intelligence are discussed.     

The Relationship Between Cardiovascular Responses in the Laboratory and in the Field

The psychophysiological responses to laboratory stressors are often examined because it is believed that such responses relate to responsiveness in real life situations. This belief has seldom been tested. The changes in heart rate, pulse transit time, and respiration rate produced by a variety of laboratory tasks (active and passive coping and physical exercise) were related to ambulatory measures of heart rate in 32 young men. The field measures were the difference in heart rate between the waking day and when asleep, and estimates of the variability of heart rate during the day, derived from time series analyses. Average changes in heart rate and pulse transit time during specific tasks did not relate consistently to heart rate in the field. However, an active coping index, derived from the ratio of the peak heart rate during an active coping task to the peak during physical exercise related to all the field measures of heart rate responsiveness. This index, which may relate to measures of additional heart rate and heightened sympathetic response to stress, also correlated positively with Trait Anxiety and elevated basal sympathetic arousal, as measured by skin conductance level. Measures of the cardiovascular response to a passive coping task, the cold pressor, and exercise did not relate to heart rate responses in the field. The findings suggest that heightened cardiac responsiveness in real life is exhibited by subjects who show elevated peak responses to active coping stressors specifically.     

Glucose-regulated protein 78 (GRP78) is elevated in embryonic mouse heart and induced following hypoglycemic stress

This study investigates the distribution and heart levels of glucose regulated protein (GRP) 78 during normal development and in response to hypoglycemia in the mouse. Results demonstrate that GRP78 is strongly expressed with in the heart, neural tube, gut endoderm, somites, and surface ectoderm of mouse embryos during early organogenesis, and GRP78 staining remains prominent in the heart from gestational days 9.5 through 13.5. Cardiac myocytes are the primary site of GRP78 expression within the heart. GRP78 levels are highest in the heart during early organogenesis and levels decrease significantly by the fetal period. GRP78 expression is increased after 24 h of hypoglycemia in the early organogenesis-stage heart. Considering the tissue specific pattern of GRP expression and changes during development of the heart, GRPs may play significant roles in the normal differentiation and development of cardiac tissue. GRP induction may also be involved in hypoglycemia-induced cardiac dysmorphogenesis. Accepted: 25 January 2000     

The Effects of Operant Heart Rate Conditioning on Cognitive Elaboration and Attitude Change

A psychophysiological investigation was conducted to assess the relationships among heart rate, affect-laden thought processes, and attitudes. Twenty subjects were trained for five days to raise and lower heart rate by means of a discriminative operant conditioning procedure. On the fifth day, communications that advocated positions with which undergraduates disagreed were presented during a raised, lowered, and basal (unaltered) heart rate trial. Results revealed that the heart rate conditioning procedure produced specific changes in heart rate, and affected the counterarguing (critical processing) to and acceptance of the persuasive communications; counterarguing and resistance to persuasion were greater during raised heart rate trials than during lowered heart rate trials. These findings are consistent with and suggest an extension of the Laceys' hypothesis concerning cardiac activity and cognitive elaboration, and provide evidence of the influence of affect-laden thought processes on evaluative reactions.     

Cardiopulmonary Adjustments During Operant Heart Rate Control

Twenty-three healthy men and women participated in a 5-session experiment in which they attempted to increase and decrease their heart rate with the assistance of visual analogue biofeedback. As a group subjects did successfully raise and lower heart rate from resting baseline. These changes in heart rate were closely paralleled by changes in V, a measure of cardiac vagal tone. Heart rate slowing was associated with increases in V, and heart rate speeding was associated with decreases in V. Respiration rate and amplitude did not differ significantly between heart rate slowing and speeding trials, and covariance analysis indicated that respiratory changes did not account for the heart rate or V effects. The weighted coherence between respiration and heart rate showed that cardiopulmonary coupling increased during heart rate slowing and decreased during heart rate speeding. Individual differences in cardiac vagal tone and cardiopulmonary coupling were unrelated to heart rate speeding and slowing performance.     

Facial and autonomic activity in depression: social context differences during imagery.

Previous research indicates that depressed patients show reduced facial expression as well as a lack of social context differences in frowning in response to sad imagery. The present study examined social context differences in facial electromyogram (EMG), self-reported emotion, skin conductance level and heart rate in 21 depressed and 22 non-depressed women assessed by the Beck Depression Inventory. Subjects were asked to imagine happy and sad situations both with and without visualizing other people. Depressed subjects showed a lack of social context differences in EMG-brow activity during sad imagery while heart rate was increased during sad-social compared to sad-solitary imagery. In contrast, non-depressed subjects showed increased EMG-brow activity during sad-social compared to sad-solitary imagery but no social context differences in heart rate. EMG-cheek activity and heart rate were increased during happy-social compared to happy-solitary imagery in depressed and non-depressed subjects. Skin conductance level was reduced in depressed compared to non-depressed subjects during baseline but failed to respond to imagery. Social context differences in heart rate and a lack thereof of frowning during sad imagery may indicate an altered psychosocial functioning in depression.     

Characteristics of heart rate fluctuations and respiratory movements during orienting, passive avoidance and flight-fight behaviour in rabbits

In the present study different heart rate patterns were demonstrated to accompany flight-fight behaviour, orienting behaviour and passive avoidance in rabbits. Flight-fight behaviour was characterized by markedly increased heart rate and diminished overall heart rate variability. The effect was mediated by vagal inhibition and beta-adrenergic activation in a type-specific relation. Orienting behaviour was accompanied by a smaller heart rate increase and the exaggeration of slow heart rate fluctuations. The latter effect was absent during beta-adrenergic blockade suggesting a behaviourally provoked beta-adrenergic activation. Single beta-adrenergic blockade did not change the characteristics of the heart rate fluctuations at rest. During passive avoidance a vagally mediated heart rate deceleration was followed by a slow heart rate return toward the initial heart rate level. This level was not reached during beta-adrenergic blockade. The enhanced overall heart rate variability during passive avoidance was mainly caused by strengthened respiratory-induced heart rate fluctuations and, furthermore, by exaggerated slow rhythmical heart rate fluctuations. The latter effect was not observed during beta-adrenergic blockade and is referred to as an orienting component within passive avoidance. Three individual behavioural types may be differentiated in rabbits 'Weisses Gross-Silber' by stable behavioural characteristics i.e. spontaneous motor activities, preferred postures at rest and coping behaviour. The results of the present study suggest that different neurovegetative reaction types, i.e. dominating beta-adrenergic or vagal activation are correlated with stable behavioural characteristics, especially in terms of preferring active or passive coping behaviour, respectively.     

Effect of substrate supply and beta-adrenergic blockade on heart glycogen and triglyceride utilization during exercise in the rat

Summary Exercise-induced heart glycogen and triglyceride mobilization was studied in control rats, in rats with reduced blood glucose supply (fasted rats), in rats with reduced plasma free fatty acids (FFA) supply (nicotinic acid-treated rats), and in rats with blockade of beta-adrenergic receptors (propranolol-treated rats). It was found in the fed control rats that both the heart glycogen and triglyceride levels were reduced at the beginning of the exercise and thereafter they returned to the control level despite the exercise being continued. The triglyceride level was reduced again during the exhaustive exercise. Reduced blood glucose supply increased the heart glycogen and triglyceride utilization during exercise. Partial prevention of the plasma FFA elevation during exercise increased the heart glycogen utilization and had no effect on utilization of the heart triglycerides. Blockade of the beta-adrenergic receptors fully prevented both the heart glycogen and triglyceride mobilization during exercise.This work was supported by the Polish Academy of Sciences, project No. 10.4.2.01.3.2.     

Effect of Feedback Delay Upon Learned Heart Rate Control

The effects of heart rate feedback delay upon bidirectional heart rate control were determined by comparing four groups of 10 subjects who received either: a) immediate feedback, or b) feedback that was delayed by 1.4 sec, 5 sec, or 14 sec. All subjects received 3 sessions of training which included 3 within-session phases, i.e. 2 (pre and post-feedback) Instructional Control phases during which subjects were instructed to speed or slow heart rate without the aid of feedback, and a Feedback phase during which bidirectional heart rate control was assisted by analogue heart rate feedback. Heart rate, chin EMG, and respiration rate were recorded during all phases. The results indicated that the magnitude of heart rate increases and decreases was systematically influenced by differing amounts of feedback delay. For increasing and decreasing heart rate, the group receiving immediate feedback showed superior heart rate control in comparison to groups which received feedback that was delayed by 14 sec. The strongest effects of feedback delay were evident during Feedback and the final Instructional Control phase. Only the group receiving immediate feedback improved HR control during Feedback and post-feedback Instructional Control phases. These findings were discussed in terms of a motor skills learning model for learned HR control. It was concluded that while many of the same parameters influence HR and motoric behavior, the two responses should not be regarded as equivalent.     

Accuracy of the LifeShirt (Vivometrics) in the detection of cardiac rhythms

The use of heart rate measures in research requires accurate detection and timing of beat-to-beat values. Numerous technologies are available to researchers; however, benchmarking of a specific apparatus is seldom conducted. Since heart rate variability provides a portal to the neural regulation of the heart, accurate detection and timing of beat-to-beat values is essential to both basic physiological research and the clinical application of heart rate variability measures. The current study evaluated the accuracy of an ambulatory system, the LifeShirt (Vivometrics), relative to a standard laboratory-based heart rate monitoring equipment (Biopac), during baseline and exercise conditions. LifeShirt performed equivalently to the Biopac during both conditions, experienced few errors of detection, generated similar times between sequential heart periods, and produced similar summary indices of heart rate and heart rate variability.     

Does motor activity during psychophysiological paradigms confound the quantification and interpretation of heart rate and heart rate variability measures in young children?

Respiratory sinus arrhythmia (RSA), heart period, and motor activity were monitored in preschoolers during a variety of tasks varying in required movement. The data analyses indicate: (1) that when activity increases during tasks, there are synchronous decreases in heart period and RSA; (2) that correlations between changes in RSA and heart period are related to activity only during exercise when there is a major demand for increased metabolic resources; and (3) that the covariation among the variables within each condition is low except during exercise. These findings suggest that the slight increases in motor activity (i.e., hand movements) often required in attention demanding psychophysiological protocols are not related to RSA and heart period responses. However, when tasks necessitate large increases in motor activity (e.g., exercise), the decreases in heart period and RSA are related to the change in motor activity.     

Sleep problems and heart rate variability over the working day

The purpose of this study was to discover whether greater sleep problems are associated with reduced heart rate variability during working hours and at night, and to determine whether this association is in part mediated by experienced affective states. This study involved 199 working women with a mean age of 33.8years. Sleep problems were assessed with the Jenkins Sleep Problems Scale, and the Day Reconstruction Method was used to measure positive affect and stress on the evening before and during the working day. Heart rate variability was indexed by the mean square root of the successive standard difference in heart period. Disturbed sleep was inversely related to heart rate variability during the working day (P=0.022), independently of demographic and behavioural confounders. Additional adjustment for positive affect and stress did not lead to further reductions in the association between sleep problems and reduced heart rate variability over the work day. Sleep problems were not predictive of reduced night-time heart rate variability. This report extends the findings from experimental studies and clinical samples, and suggests that disturbed sleep might impair heart rate variability in real life settings, in particular during working hours. Reduced heart rate variability might be a potential pathway linking sleep problems with cardiovascular disease. Based on the current data there was little evidence that the inverse associations between sleep problems and heart rate variability were mediated by experienced affective states.     

A Comparison of Additional Heart Rates During Active Psychological Challenge Calculated From Upper Body and Lower Body Dynamic Exercise

Heart rate, oxygen consumption, and blood pressure were recorded while 22 young males performed a stressful mental arithmetic task and played a video game. Measurements were also made while subjects undertook two separate graded dynamic exercise tasks, an upper body and a lower body task. All measures changed as a function of psychological challenge, and during exercise heart rate and oxygen consumption changed as an orderly function of workload. For each subject, heart rate was plotted against oxygen consumption over the various workloads for each exercise task separately, thereby generating two regression lines per subject. In conjunction with oxygen consumption values during the psychological tasks, these regressions allowed the prediction of expected heart rate values during psychological challenge, and thus the computation of additional heart rate as the difference between actual heart rate and predicted heart rate. Actual heart rate during psychological challenge was substantially greater than predicted heart rate, i.e., there was considerable additional heart rate. This was the case irrespective of whether upper or lower body exercise was used to compute the predictions, and there was no significant difference between the additional heart rates generated from the two exercise tasks, which produced regression lines with similar slope and intercept values.