Reactivity of immune, endocrine and cardiovascular parameters to active and passive acute stress

This study clarified associations among immune, autonomic, and endocrine activities during mental arithmetic and cold pressor stress tasks in 26 women in the follicular phase. Both tasks decreased CD3+ T cells, CD4+ T cells, and CD19+ B cells, whereas they increased lymphocytes, granulocytes, NK cells, and NK cell activity (NKCA). The mental arithmetic task had a greater impact than the cold pressor task on changes in CD3+ T cells and in NK cells. Cardiovascular reactivity to active stress was associated with increased NK cells and decreased CD3+ T cells. Reduced cortisol levels during passive stress were associated with decreased CD19+ B cells and with increased NK cells. The merits of this study are that it controlled the following factors. Perceived stress during the two tasks was matched; both tasks lasted long enough to elicit high-magnitude responses; and the length of the intervening rest period minimized probable carryover effects between tasks.     

Causal coherence analysis of heart rate variability and systolic blood pressure variability under mental arithmetic task load

Causal coherence analysis based on a closed-loop bivariate autoregressive model was applied to heart rate variability and systolic blood pressure (SBP) variability during mental arithmetic tasks to clarify how mental task load affects the linear closed loop interaction between cardiac and vascular systems. Thirteen normal male subjects performed a mental arithmetic task, button press task, and rest task while measuring their RR interval (RRI) and SBP. The mean value in the low frequency (LF) band (0.04-0.15Hz) of the squared causal coherence function from SBP to RRI during the mental arithmetic task was significantly higher than during the other two control tasks. Conversely, the LF band of the squared causal coherence function from RRI to SBP during the mental arithmetic task tended to be lower than during the rest task. These results suggest that mental arithmetic tasks enhance linear causal coupling from the vascular to cardiac system, and conversely weaken that from the cardiac to vascular system.     

Evaluation of Myocardial and Peripheral Vascular Responses During Reaction Time, Mental Arithmetic, and Cold Pressor Tasks

The primary purpose of this study was to examine the covariation of cardiac output and forearm blood flow during reaction time, mental arithmetic, and cold pressor tasks. Cardiac output was indexed using impedance cardiography, whereas impedance venous occlusion plethysmography was used lo index forearm blood flow. Cardiac output increased significantly over resting values in all three tasks, hut the pattern of these increases differed. Large heart rate increases during mental arithmetic and cold pressor tasks more than offset stroke volume decreases; the increases in the reaction time task were due to relatively smaller heart rate increases with stroke volume augmentation. For forearm blood flow, all task levels were higher than resting levels, but only mental arithmetic levels were statistically higher. The correlation between cardiac output and forearm blood flow change was significant for the reaction time task, but not for the mental arithmetic or cold pressor tasks.     

Cardiovascular reactivity assessment: effects of choice of difficulty on laboratory task responses.

This laboratory study of cardiovascular reactivity was designed to examine how a choice of difficulty element in a mental arithmetic task would affect cardiovascular responses. 20 healthy male subjects were tested on a computer-controlled mental arithmetic task, designed to standardize performance across subjects by keeping constant the proportion of correct responses. This was achieved by automatic adjustment of problem difficulty according to ongoing performance. Subjects were led to believe that they could take either a 'difficult' or an 'easy' version of the mental arithmetic task and were asked to make a choice; in fact, all subjects were given the same task. Subjects who chose the 'difficult' mental arithmetic task (N = 10) showed significantly greater increases in myocardial contractility, cardiac output and systolic blood pressure during task performance than those who chose 'easy' (N = 10). However, subjects who chose 'difficult' were presented with more difficult problems presumably due to their exerting greater levels of effort during the task. The differences in cardiovascular responses associated with choice of difficulty were absent during testing on four subsequent tasks which did not incorporate any choice options (reaction-time, speech, mirror trace, cold pressor). These findings are interpreted as being provocative, rather than in any way conclusive. Nevertheless, they are suggestive of the possibility that choice of difficulty in laboratory tasks may be one strategy for improving the ecological validity of laboratory reactivity assessment procedures.     

心算实验中事件相关去同步化脑电变化初探

目的：探讨事件刺激处理时心理活动的脑电生理改变。方法：应用脑电地形图的检测技术对３０例正常人安静状态及在两种作业难度下脑电功率值的变化进行观察。结果：①事件刺激后α２频带功率值降低,β、α１频带功率值增高,变化以枕区、顶区、后颞区的功率值最为显著;②随作业难度的增加α２频带功率呈梯度降低,β频带功率则呈梯度增高;③在心算过程中,安静状态下呈现的两侧半球电位值差异消失。结论：心算期间大脑皮层出现事件相关去同步化,并存在区域性差异。更高作业难度将导致更广泛更持久的脑电去同步化     

Effects of mental workload on long-latency auditory-evoked-potential,salivary cortisol,and immunoglobulin A

This paper researches on the effects of mental workload on long-latency auditory-evoked-potential (AEP), salivary cortisol, and immunoglobulin A (IgA). 20 Healthy subjects (11 males and 9 females) participated in the experiment voluntarily. The mental task consisted of two parts: arithmetic task and reading comprehension task. The Latencies of N1, P2, N2, P3, and mismatch negativity (MMN) all increased significantly after the mental tasks were adopted at all of the three recording sites: Cz, Fz, and Pz (p < 0.05). In this experiment, changes of salivary cortisol and s-IgA levels due to mental tasks were not significant. With the introduction of mental tasks, more processing resources are allocated to the primary task (mental task), and decreased processing resources available for the secondary task (auditory task), which is reflected on the increases in the latencies of probe-evoked AEP components.     

Genetic and environmental contribution to postural balance of older women in single and dual task situations

The purpose of the present study was to examine the effect of a second task on postural balance and to determine the role of genetic influences on postural balance when dual tasking among 206 monozygotic and 227 dizygotic female twins, aged 63-76 years. Balance was measured as medio-lateral and antero-posterior velocity of the centre of pressure (COP) (mm/s) and velocity moment (mm(2)/s) while standing on a force platform. Doing an arithmetic task increased movement of the COP while the hand motor task had no effect on movement of the COP. The genetic contribution to balance in the single task situation was minor (14%, 95% confidence interval, CI: 11-35%) whereas in the dual task situation it was moderate (28%, 95% CI: 0.02-42%). The finding can be explained in the light of the underlying phenotypes of dual tasking, such as cognitive processing that is found to be under considerable genetically controlled even in old age. Moreover, the present study supports previous studies suggesting that, especially among older people, when simultaneously maintaining balance and performing another cognitively demanding task, additional central processing is recruited.     

Movement sway: changes in postural sway during voluntary shifts of the center of pressure

We introduce a method for quantification of movement sway—spontaneous migrations of the center of pressure (COP) during its voluntary shifts. Subjects stood on a force platform or on a board with a narrow support surface ("unstable board") and performed voluntary cyclic shifts of the COP at different frequencies. Movement sway was typically higher than postural sway; sway in the mediolateral direction was particularly increased. Movement sway showed a drop with the frequency of voluntary COP shifts. During standing on the unstable board, postural sway increased while movement sway decreased. The effects of task parameters were stronger on the sway component in the direction of the voluntary COP shift than in the orthogonal direction. We interpret changes in movement sway with task parameters as partly resulting from modulation of the search function of sway during voluntary COP shifts. Electronic Publication     

Blunted cardiovascular reactions are a predictor of negative health outcomes: A prospective cohort study

The study examined whether cardiovascular responses to psychological stress tests predict future anxiety and depression scores 40‐months later. Hemodynamic measures were obtained from 102 healthy adults before, during and after mental arithmetic, a speech task, and a cold pressor task. The 14‐item Hospital Anxiety and Depression Scale was administered at initial testing and at 40‐months follow‐up. At initial testing analyses revealed that high anxiety symptoms were characterized by blunted cardiovascular reactions to acute mental stress, particularly mental arithmetic. Furthermore, after adjustment for baseline blood pressure (BP ), baseline anxiety levels and traditional risk factors, attenuated systolic BP responses to mental arithmetic were associated with future anxiety levels (ΔR ² = .055). These findings suggest that blunted cardiovascular reactions to stress may be an independent risk factor for future anxiety levels.     

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.     

Instantaneous changes in heart rate regulation due to mental load in simulated office work

The cardiac regulation effects of a mental task added to regular office work are described. More insight into the time evolution during the different tasks is created by using time–frequency analysis (TFA). Continuous wavelet transformation was applied to create time series of instantaneous power and frequency in specified frequency bands (LF 0.04–0.15 Hz; HF 0.15–0.4 Hz), in addition to the traditional linear heart rate variability (HRV) parameters. In a laboratory environment, 43 subjects underwent a protocol with three active conditions: a clicking task with low mental load and a clicking task with high mental load (mental arithmetic) performed twice, each followed by a rest condition. The heart rate and measures related to vagal modulation could differentiate the active conditions from the rest condition, meaning that HRV is sensitive to any change in mental or physical state. Differences between physical and mental stress were observed and a higher load in the combined task was observed. Mental stress decreased HF power and caused a shift toward a higher instantaneous frequency in the HF band. TFA revealed habituation to the mental load within the task (after 3 min) and between the two tasks with mental load. In conclusion, the use of TFA in this type of analysis is important as it reveals extra information. The addition of a mental load to a physical task elicited further effect on HRV parameters related to autonomic cardiac modulation.     

Performing Mental Arithmetic Increases Total Respiratory Resistance in Individuals with Normal Respiration

The effect of performing mental arithmetic problems on total respiratory resistance was examined in 30 male college students. Each student was assigned to one of two conditions: those in one group performed an easy arithmetic task whereas those in the other group performed a difficult arithmetic task. Total respiratory resistance, measured with the forced oscillation technique, increased more in individuals who performed the difficult arithmetic task than it did in individuals who performed the easy arithmetic task. These findings are consistent with respiratory resistance changes exhibited by asthmatic patients under conditions of stress.     

The effect of noise interference, type of cognitive stressor, and order of task on cardiovascular activity

In the search for reliable, easily applicable mental stressors many researchers have investigated the propensity of mental arithmetic and Stroop color discrimination tasks to elicit a physiological stress response; some researchers have added noise interference with the expectation of larger response magnitudes. The present study investigates a number of previously untested questions by directly comparing cardiovascular responses to mental arithmetic or the Stroop task with and without noise interference in a sample of 66 young adults. Half of all subjects were exposed to the additional noise interference, all subjects responded to both types of mental stressors. Blood pressure responses did not discriminate among the stressors but noise interference consistently augmented heart rate responses during mental arithmetic. Response to the second, repeated stressor was associated with highly significant response habituation effects for blood pressure. Furthermore, when mental arithmetic was presented first, both tasks elicited comparable and large responses; when the Stroop test was presented first both tasks triggered smaller responses but of comparable magnitude. Subjective evaluations of the stressors were not predictive of overall physiological response.     

Secretory immunoglobulin A and cardiovascular activity during mental arithmetic: effects of task difficulty and task order

Secretory immunoglobulin A (sIgA) in saliva and cardiovascular activity were measured at rest and during mental arithmetic. Task difficulty was manipulated by presenting easy, hard, and impossible versions of the mental arithmetic task in counterbalanced order, while task novelty was operationalised as order of presentation (i.e. first, second, third). Mental arithmetic elicited significant increases in sIgA concentration and sIgA secretion rate, as well as significant cardiovascular effects. Performance decreased and rated difficulty increased with increasing task difficulty. However, sIgA and cardiovascular activity, with the exception of diastolic blood pressure, were insensitive to variations in task difficulty. In contrast, sIgA concentration and a broad range of cardiovascular variables were influenced by task novelty, with more pronounced activity characterising the task version presented first, irrespective of its level of difficulty. Task novelty would seem to be a more important determinant of sIgA and cardiovascular activity than task difficulty.     

A comparative evaluation of heart rate reactivity during MATH and a standard mental arithmetic task

Heart rate was monitored while 20 young males completed MATH, a computer-operated mental arithmetic task specifically designed for use in experiments involving subjects of heterogeneous numerical ability, and a standard mental arithmetic task used in this laboratory on several occasions. Both tasks elicited sizeable increases in heart rate, and comparison of subjects' reactivity scores revealed significant inter-task consistency of reaction.     

THE EFFECT OF COGNITIVE TASKS AND VERBALIZATION INSTRUCTIONS ON HEART RATE AND SKIN CONDUCTANCE

This study investigated the effects of cognitive tasks and verbalization instructions on heart period (HP) and skin conductance (SC). Two tasks (imagining common scenes and solving mental arithmetic puzzles) were used to test the hypothesis that conditions requiring attention to internal processess (rejection of the environment) are accompanied by cardiac acceleration and SC increases. Each type of task was administered under three instruction conditions: no verbalization, later verbalization and concurrent verbalization. It was found that the imagination task was associated with no significant changes in HP or SC unless the S was preparing to talk or actually talking. Mental arithmetic resulted in cardiac acceleration and SC increase even when no verbalization was required; however, this result is perhaps due to the covert verbalization inherent in the process of solving mental arithmetic problems. Both later and concurrent verbalization also produced significant increases in physiological activation during the arithmetic task. The findings of this study do not support the notion that conditions requiring rejection of the environment are associated with specific physiological changes. Rather the changes are generally attributable to the verbalization requirement. The effects of instructions requiring S to verbalize later are interpreted as due to either a motor set phenomenon or fear of being evaluated while talking.     

Cardiovascular and neuroendocrine adjustment to public speaking and mental arithmetic stressors

In this study, we evaluated cardiovascular. neuroendocrine, and psychological adjustment to repeated presentations of a public speaking and a mental arithmetic task. Brief versions of mental arithmetic tasks have been used widely in previous reactivity studies, and growing attention to more socially salient tasks has led to the increased use of public speaking tasks. However, psychophysiological adjustment during extended and repeated exposure to these tasks has not been delineated. In the present study, 52 healthy men worked on three 8-min presentations of public speaking and of mental arithmetic in a repeated measure design. Both tasks produced substantial cardiovascular, adrenocorticotropic hormone, and cortisol responses; public speaking produced greater changes. Repeated presentations of public speaking produced a stable pattern of cardiac activation, whereas repetitions of the mental arithmetic initially produced large cardiac responses that changed to a more vascular tonus across task periods. Both tasks increased negative moods. However, correlations between the endocrine, cardiovascular, and negative moods were significant only during the public speaking stressor. The public speaking task is a socially relevant experimental protocol for studying reactivity in the laboratory setting and elicits relatively high, stable, and homogeneous responses.     

Task-induced ST segment depression, ectopic beats, and autonomic responses in coronary heart disease patients

The relationship between psychologically induced autonomic responses, ST segment depression, and ectopy was examined in patients with coronary artery disease (CAD) and controls. Both groups underwent a battery of performance tasks and interviews. Performance tasks were selected to yield predictable sympathetic and vagal responses. Autonomic activation in response to stimuli was documented using heart rate, blood pressure, and vascular indices. ST segment depression was observed in a significant portion of the sample. In subjects with CAD, ST segment depression, but not ectopy, was specifically associated with mental arithmetic. In this task, autonomic changes occurred, suggesting beta sympathetic activation. The prevalence of ST segment depression during mental arithmetic declined when a task-inducing brief, phasic vagal activation was combined with the mental arithmetic. Ectopic beats were not associated with a specific task among either patients or controls. The results supported the importance of psychologically induced autonomic response for the precipitation and inhibition of ST segment depression in patients with CAD.     

Assessment of Baroreceptor Reflex Function During Mental Stress and Relaxation

This paper describes a method of measuring baroreceptor cardiac reflex sensitivity noninvasively from spontaneous patterns of blood pressure and interbeat interval, and the application of this technique in psychophysiology. Baroreflex function was assessed in 24 female volunteers during relaxation and performance of the cold pressor test and a non-verbal mental arithmetic task. Blood pressure and interbeat interval were monitored continuously from the finger using the vascular unloading technique. Sequences of three or more cardiac cycles were identified over which systolic blood pressure increased progressively in conjunction with lengthening interbeat interval, or systolic blood pressure decreased as interbeat interval was reduced. The regression between systolic blood pressure and interbeat interval was computed as an index of baroreflex sensitivity. Relaxation was associated with a small prolongation of interbeat interval, whereas baroreflex sensitivity increased from 17.1 to 19.8 ms/mmHg. Baroreflex sensitivity was reduced significantly during mental arithmetic (mean 14.2 ms/mmHg) but not during the cold pressor test (mean 17.4 ms/mmHg). The difference between mental arithmetic and the cold pressor test may be related to the relative intensity of cardiac and vascular responses in the two situations. The implications of these results for the understanding of behavioural influences on haemodynamic function are discussed and the advantages of noninvasive methods are considered.     

Contributions of delayed visual feedback and cognitive task load to postural dynamics

In this experiment, we examined the extent to which postural control is influenced by visual and cognitive task performance. Fourteen healthy young participants performed a balance task in eyes-open (EO) and delayed visual feedback (DVF) conditions. DVF was presented at delays ranging from 0 to 1200 ms in 300 ms increments. Cognitive load was implemented by a simple, serial arithmetic task. High and low-pass filtering (f_c = 0.3 Hz) distinguished LOW and HIGH frequency components, which were used to compute the variability of Anteroposterior (AP) Center of Pressure (COP) trajectories on fast (>0.3 Hz) and slow (<0.3 Hz) times cales. Imposed visual delay increased sway variability at both LOW and HIGH components. Cognitive task performance, however, influenced only the variability of fast (HIGH) sway components. Our results support distinct timescale mechanisms for postural control, but also demonstrate that vision predominantly influences low frequency components of postural sway. Moment-to-moment COP fluctuations are dependent on cognitive performance during delayed visual feedback postural control.