Stable T wave effects during improvement of heart rate control with biofeedback

The short Sing-a-Song Stress Test: A practical and valid test of autonomic responses induced by social-evaluative stress

The Sing-a-Song Stress Test (SSST) was recently developed as an alternative to the Trier Social Stress Test (TSST) to investigate autonomic nervous system responses to social-evaluative stress. In the SSST, participants are suddenly cued to sing a song in the presence of confederates. However, the SSST is still quite long (~15 min) and the requirement for confederates makes it labor-intensive. The current study tested whether a shorter (~6.5 min), single-experimenter, version of the SSST can still reliably elicit subjective and physiological stress reactivity. Our sample consisted of 87 healthy young adult participants (age range: 18-35 years). During the short SSST and a speeded reaction time task, in which aversive loud tones were to be avoided (TA), we measured heart period (HP), sympathetic nervous system (SNS) activity using pre-ejection-period (PEP), skin conductance level (SCL), and non-specific skin conductance responses (ns.SCR), and parasympathetic nervous system (PNS) activity using respiratory-sinus-arrhythmia (RSA) and the root-mean-square of successive differences (RMSSD). The short SSST induced significant decreases in positive affect and increases in negative affect. MANOVAs on the clusters of SNS and PNS variables showed that the short SSST elicited significant HP (-118.46 ms), PEP (-7.76 ms), SCL (+4.85 μS), ns.SCR (+8.42 peaks/min) and RMSSD (-14.67) reactivity. Affective, SNS, and PNS reactivity to the new SSST social-evaluative stress task were of comparable magnitude to that evoked by the TA mental stressor. We conclude that the short SSST is a valid and cost-effective task for large scaled studies to induce social-evaluative stress to a sufficient degree to evoke measurable changes in PNS and SNS activity and affective state.

Ambulatory measurement of the ECG T-wave amplitude

Ambulatory recording of the preejection period (PEP) can be used to measure changes in cardiac sympathetic nervous system (SNS) activity under naturalistic conditions. Here, we test the ECG T-wave amplitude (TWA) as an alternative measure, using 24-h ambulatory monitoring of PEP and TWA in a sample of 564 healthy adults. The TWA showed a decrease in response to mental stress and a monotonic decrease from nighttime sleep to daytime sitting and more physically active behaviors. Within-participant changes in TWA were correlated with changes in the PEP across the standardized stressors (r = .42) and the unstandardized naturalistic conditions (mean r = .35). Partialling out changes in heart rate and vagal effects attenuated these correlations, but they remained significant. Ambulatory TWA cannot replace PEP, but simultaneous recording of TWA and PEP provides a more comprehensive picture of changes in cardiac SNS activity in real-life settings.

Differences in autonomic physiological responses between good and poor inductive reasoners

We investigated individual- and task-related differences in autonomic physiological responses induced by time limited figural and verbal inductive reasoning tasks. In a group of 52 participants, the percentage of correctly responded task items was evaluated together with nine different autonomic physiological response measures and respiration rate (RR). Weighted multidimensional scaling analyses of the physiological responses revealed three underlying dimensions, primarily characterized by RR, parasympathetic, and sympathetic activity. RR and sympathetic activity appeared to be relatively more important response dimensions for poor reasoners, whereas parasympathetic responsivity was relatively more important for good reasoners. These results suggest that poor reasoners showed higher levels of cognitive processing intensity than good reasoners. Furthermore, for the good reasoners, the dimension of sympathetic activity was relatively more important during the figural than during the verbal reasoning task, which was explained in terms of hemispheric lateralization in autonomic function.

Physiological responses in high-P subjects during active and passive coping

There have been relatively few studies of the psychophysiological correlates of Eysenck's dimension of psychoticism (P) and those which do not exist report findings which cannot be readily integrated to isolate a distinctive physiological basis of P. The present study investigated differences between subjects scoring high and low on the P scale of the Eysenck Personality Questionnaire (EPQ) in relation to sympathetic and parasympathetic arousal following aversive stimulation. An active-passive coping paradigm using an aversive tone was selected to elicit responses and cardiovascular measures (heart period, heart period variance, T-wave amplitude) and a skin conductance measure (event-related skin conductance) were obtained. The findings show that differences between high- and low-P subjects are specific to the coping condition. Under active coping, high-P subjects exhibited greater sympathetic arousal following the aversive tone than low-P subjects. There was no significant difference between the high-P and low-P subjects on any physiological variable under the passive coping condition. It is suggested that if there is differential functioning of the divisions of the autonomic nervous system in subjects differing in P, that these differences may only manifest themselves under specific situations.

T-wave amplitude utility revisited: some physiological and psychophysiological considerations

The last decade has seen some quite polemicized discussions concerning the utility of T-wave amplitude as a psychophysiological measure, but more recent reports indicate that we are now moving into a more empirically oriented and analytic examination of this topic. Such a report is one by Contrada et al. (1989), who manipulated sympathetic (beta-adrenergic) influences both pharmacologically and behaviorally, and whose main conclusion was that their results "support the hypothesis that T-wave is significantly affected by beta-sympathetic influence on the heart". However, we question their other conclusion that "a nonspecific effect of heart rate change on T-wave amplitude would also account for these results", and also suggest that their discussion of the "implications for the utility of T-wave amplitude in psychophysiological research" bears further consideration. In particular, for psychophysiologists, of fundamental importance is the distinction between T-wave amplitude's utility as a physiological index and its utility as a psychophysiological index. Concerning the former issue, we consider: (a) the alpha/beta adrenergic distinction, (b) inappropriate T-wave amplitude augmentation effects to sympathomimetic stimulation, (c) the nonspecific-response-to-tachycardia argument, and (d) the view of pulse transit time as a criterial standard, rather than as a candidate index. Regarding the issue of psychophysiological index utility, we consider: (a) dependent-variable sensitivity, drawing a further distinction between reactive and specific sensitivity, and (b) independent-variable-manipulation effectiveness.

Cardiac sympathetic and parasympathetic activity during self-regulation of heart period

Fourteen subjects attempted to increase and 15 attempted to decrease cardiac interbeat interval (IBI) while being provided with biofeedback of IBI, T-wave vector magnitude (TWVM), or respiratory sinus arrhythmia (RSA). Subjects in both groups showed directional change in IBI relative to a tracking control task, but the three types of feedback did not differentially affect performance. Voluntary IBI increases were associated with significant increases in TWVM and RSA, and voluntary IBI decreases were associated with significant reductions in RSA and nonsignificant reductions in TWVM. This pattern of results suggests that alterations in cardiac vagal tone are involved in voluntary IBI increase and decrease tasks. The results also suggest a role for cardiac sympathetic nervous activity in voluntary IBI increase. The role of changing respiration cycle period was also investigated.

Responses of the T-wave amplitude as a function of active and passive tasks and beta-adrenergic blockade

This paper presents evidence that phasic changes in T-wave amplitude vary as a function of task conditions and beta-adrenergic drugs. Three experiments were designed to test the sensitivity of T-wave amplitude to manipulations in sympathetic arousal. In the first experiment, T-wave amplitude was recorded during an active behavioral task in which 32 subjects believed that they could control the duration of an aversive white noise and during a passive behavioral task in which another 30 subjects knew that they had no control. T-wave amplitude decreased to a greater extent in the active behavior group than in the passive group. In the second experiment, 9 subjects receiving one of two beta-adrenergic blockers and 10 subjects receiving placebo completed the active task. Task-induced reductions in T-wave amplitude were systematically blocked by the beta blockers. In the third experiment, 5 subjects received placebos and 15 received one of two different beta blockers. All subjects performed a mental arithmetic task. Subjects receiving a placebo, but not those receiving beta blockade, exhibited a significant reduction in T-wave amplitude during mental arithmetic.

Changes in the T-wave vector loop of the three-dimensional vectorcardiogram during exposure to cold pressor stress

Three-dimensional vectorcardiography was used to characterize changes in the T-wave vector loop during exposure to cold pressor stress. Data were collected from 8 subjects during baseline, cold pressor, and recovery periods. Maximum vector length, polar angle of the longest vector, azimuth angle of the longest vector, sum of all vectors, polar angle of the vector sum, azimuth angle of the vector sum, surface area of the loop, and maximum distance between adjacent vectors were computed from the T-wave vector loop. The amplitude of the one-dimensional T-wave (TWA) was also computed. Interbeat interval and TWA decreased during hand immersion and increased during recovery. Of the vectorcardiographic measures, only maximum vector length and vector sum showed statistically significant change; both decreased during the task and returned to baseline during recovery. TWA accounted for 46% of the task related variance compared to 53% and 47% respectively, for vector sum and maximum vector length. Changes in TWA probably reflect a true change in cardiac electrical potential rather than a change in T-wave vector loop shape or orientation.

The human dive reflex: an experimental, topographical and physiological analysis

This study examined the eliciting conditions, response topography and autonomic nervous system (ANS) control of the dive reflex as evoked in humans. Twenty-four subjects received eight trials in each of the three treatment conditions: breath holding without face immersion (BH); face immersion without breath holding (FI); and the "full dive" FIBH condition. It was the combination of both FI and BH in 23 +/- 0.5 degrees C water that was necessary to elicit the dive reflex. A precise topographical analysis differentiated the FIBH condition from the FI and BH control conditions in terms of the emergence of a secondary component initiated approximately 12 seconds after trial onset. During this secondary component, augmentation of bradycardic (mean = 16.3 bpm) and digital vasoconstrictive (mean = -24.9%) responses were maintained throughout the duration of the 40-second dive. A joint consideration of the heart rate and the T-wave amplitude measures as indices of the action of both branches of the ANS suggested that the dive reflex involves concurrent sympathetic and parasympathetic activation. A potential conditioning application of the dive reflex for countering paroxysmal supraventricular tachycardia was discussed.

Effects of electrode placement on direction of T-wave amplitude changes in psychophysiological studies

Psychophysiological studies, which measure small changes in T-wave amplitude (TWA) induced by behavioral manipulations, usually employ a single electrode placement for obtaining the ECG. The present study varied electrode placement (EP) within subjects among three EPs that have been reported in the literature (a lead-II limb placement, and two chest placements) to determine whether, as has been claimed, the direction of TWA changes can be changed by varying EP. Both HR and TWA were monitored in 24 males during the Baseline, Listen, and Task phases of an iterative subtraction task. The EP variation did not affect the direction of TWA change. Reliable TWA attenuation accompanied by HR acceleration was observed in all leads.

Cardiac responses to psychological tasks: impedance cardiographic studies

In a series of studies, cardiac activity, assessed with an impedance cardiograph, was monitored as college students performed either a visual search or pursuit rotor task. Heart rate, systolic time intervals, stroke volume, cardiac output and the Heather (1969) index of contractility were measured before, during and after performance. In the first study, visual search did not affect the participants' (N = 44) level of cardiac output or their length of the pre-ejection period. It is likely that the lack of charge in cardiac output resulted from a fall in stroke volume and in the Heather index while the task was performed. Heart rate was most rapid during performance and emerged as the only measure affected by the withdrawal of monetary incentives for failure to solve the visual search problem. In the second study, 40 subjects performed a pursuit rotor task and increases in cardiac output as well as changes in all of the other cardiac measures occurred. The level of task difficulty influenced the extent of heart rate increases and stroke volume decreases during performance. An additional 20 male subjects participated in a third study in which the level of difficulty of the pursuit rotor task was signalled and the order of the levels of difficulty was balanced across trial blocks. Under these conditions, the changes in cardiac activity before, during and after performance were similar to those observed in the first two studies. Heart rate was the only measure sensitive to the level of task difficulty. In general, the findings underscore the sensitivity of heart rate to changes in subtle aspects of psychological situations. To enlist increases in cardiac output and inotropic parameters extensive alterations in behavioral state are required.

Intuitive and factual approaches in the comparison of contractility and repolarization measures of sympathetic myocardial activity

Obrist (Cardiovascular Psychophysiology: A Perspective, Plenum Press, New York, 1981) has recently argued for the superiority of contractility (e.g. pulse transit time) over ventricular repolarization (e.g. T-wave amplitude) measures as indices of sympathetic myocardial influences on the grounds that the T-wave occurs during the diastolic portion of the cardiac cycle (in contrast to the systolic temporal locus of contractile-based measures). This note suggests that this argument is intuitively rather than factually based because it lacks both logical and empirical validity.

Psychophysiological and physiological aspects of T-wave amplitude in the objective study of behavior

The objective study of behavior, which is the stated aim of our society, does not impose restrictions on the levels of explanatory constructs that are used. The only restriction is that the evidence concerning those constructs be stated in an objective or scientifically communicable way. Thus the concepts that we employ to explain behavior range from the sociologic to the biochemical. This article's underlying thesis is that behavior needs to be investigated at various levels, and that these levels should be clearly differentiated in order to bring these investigations into a scientifically meaningful relationship. The thesis is here illustrated by examining evidence and arguments concerning the utility and status of a noninvasive index of myocardial performance: T-wave amplitude (TWA). The examination begins at a psychophysiological-index level, wherein TWA is considered in terms of how well this noninvasive physiological index differentiates psychological processes. Secondly, at a lower physiological-index level, we consider the assumption that TWA reflects a relatively unitary physiological process, myocardial beta-adrenergic sympathetic influence. Both the grounds for and implications of this assumption are discussed. Finally, at the physiological-index level of discourse, brief reference is made to the mechanism by which changes in beta-adrenergic sympathetic innervation may produce correlated changes in TWA. The overall aim of the article is to differentiate these three levels of investigation, and yet also to consider the interrelationship among these three levels in order to provide a fuller scientific understanding of the phenomena involved.

The effects of anticipatory stress on heart rate and T-wave amplitude

The purpose of the present study was to examine the effects of an anticipatory stressor on three measures of cardiovascular activity: heart rate (HR), T-wave amplitude (TWA) and blood pressure (BP). Twenty-eight males were assigned to either a stress or no-stress group. All subjects reviewed a brief section of prose and then read it aloud during two sessions. The stress group was told that the reading task was a speech and that their performance would be evaluated. The no-stress group was told that the reading task was a part of the readability evaluation of the text material. Reliable increases in HR were observed during both sessions with the stress group exhibiting greater accelerations than the no-stress group. Though TWA and BP varied with periods, no reliable group differences were observed. Degree of threat or aversiveness appears to be indexed more reliably by HR changes than by changes in TWA.

Biofeedback training of cardiac acceleration; effects on airway resistance in bronchial asthma

Twenty-four volunteers adolescent and adult asthmatics were pre-tested for suggestibility and retained for an investigation of the airway effects of biofeedback induced voluntary cardiac acceleration. Eight subjects were successful in achieving large magnitude voluntary cardiac acceleration after 2-5 training sessions. Eight matched control group subjects received one session of biofeedback assisted training in cardiac constancy. Results revealed that large magnitude heart rate increase was accompanied by a statistically significant increase in Peak Expiratory Flow Rate for experimental group subjects. Control group subjects showed a drop in heart rate and a statistically insignificant drop in PEFR. Clinical records for experimental and control group subjects during the pre- and post-training periods revealed that a significant reduction in the incidence of attacks, the use of p.r.n. medication, and the index of medication use per attack occurred in trained subjects. No change on any of these criteria occurred for control group subjects. The acquisition of the cardiac acceleration response of asthmatic experimental group subjects was compared with the acquisition rate of a matched group of normal subjects receiving one session of biofeedback training. No differences were revealed between the groups in the rate of acquisition. However, symptom-free asthmatics were shown to have PEFR readings significantly below those of the normal group, thus supporting previous findings. The possible implications of these findings for the clinical management of bronchial asthma, are discussed.

Cardiac and forearm plethysmographic responses to high intensity auditory stimulation

This paper reports an investigation of forearm blood flow and cardiac responses to high intensity auditory stimulation. Blood was assessed in terms of forearm girth (FG) using a strain gauge, and since this technique had not been used previously, a preliminary study was conducted to validate the measure. In Experiment 1 (N = 24), subjects performed either a fast- or slow-paced mental arithmetic task. The data indicated that the strain gauge technique differentiated periods of rest from arithmetic stress and produced results comparable with those obtained using limb volume plethysmography. In Experiment 2 (N = 24), subjects received eight presentations of either a 60 dB or a 110 dB white noise stimulus at randomly ordered intervals of 35, 40, 45 and 50 sec; stimulus rise time was 50 msec and the duration 1 sec. Both groups displayed short-latency (i.e. within 10 beats poststimulus) cardiac accelerative responses which habituated over trials. In addition, the 110dB group displayed a long-latency (19.9 sec) accelerative response of approximately 25 beats per min and this was accompanied by an increase in FG. These responses occurred only following the first stimulus presentation, and analysis of the EKG T-wave amplitude suggested that the cardiac response was mediated sympathetically. These results are discussed in terms of conceptions of the startle and defence responses in man and the fight/flight reaction in animals.