Changes in indexes of cardiovascular system in different mental tasks

The influence of different types of mental activity on the cardiovascular system was analyzed by following indexes: the heart rate (HR), the variation magnitude (VM), the amplitude of systolic wave (SWA) and the pulse wave transit time (PWTT). A registration of these indexes was conducted when the subjects solved verbal-logical and spatial mental tasks. HR was significantly greater in the spatial tasks than in the verbal-logical tasks, while SWA had an inverse relationship. The time for solving of tasks of the both types did not differ significantly. Therefore, the observed changes in autonomic indexes were not related to a difficulty of the mental tasks, but depended on the specific cognitive processes involved in the mental tasks of different types. Thus, the observed change in HR and the decrease in SWA correlating with the blood pressure rise reflect an influence of the sympathetic nervous system on the heart work during mental tasks of the verbal-logic type. The obtained results suggest that the indexes of HR and a blood pressure may also serve as supporting criteria in a development of new technologies for a determination of different types of mental operations in addition to the rhythms of the brain electrical activity.     

The effect of mental loads on muscle tension, blood pressure and blink rate

Surface electromyogram (EMG), blood pressure (BP), blink rate (BR) and heart rate (HR) were recorded before and during 4 types of mental task. The mental task involved 3 tasks that encompassed the memory (M), visual search (VS) and color-word (CW) tasks besides the control task (CT) of maintaining a similar posture while focusing on a single spot on the computer screen. Except for CW, any voluntary movement for response to visual stimuli given were not demanded. Slightly but significant increases in integrated EMG (iEMG) were shown in terapezius, biceps and gastrocnemius muscles during tasks except for CT. Especially in the trapezius muscle during M, the most remarkable enhancements of iEMG and BP were shown. In VS and CW tasks, significant decreases in BR were observed, although in M and CT tasks there were no significant changes in it. There were no significant changes in HR in any type of tasks. The present study demonstrated the increase in muscle tension due to mental needs of cognitive tasks per se accompanying changes in BP and BR. And, enhancement of these physiological responses by memory loads and eyeball movement was discussed as a possible mechanism.     

Monitoring Cognitive and Emotional Processes Through Pupil and Cardiac Response During Dynamic Versus Logical Task

The paper deals with the links between physiological measurements and cognitive and emotional functioning. As long as the operator is a key agent in charge of complex systems, the definition of metrics able to predict his performance is a great challenge. The measurement of the physiological state is a very promising way but a very acute comprehension is required; in particular few studies compare autonomous nervous system reactivity according to specific cognitive processes during task performance and task related psychological stress is often ignored. We compared physiological parameters recorded on 24 healthy subjects facing two neuropsychological tasks: a dynamic task that require problem solving in a world that continually evolves over time and a logical task representative of cognitive processes performed by operators facing everyday problem solving. Results showed that the mean pupil diameter change was higher during the dynamic task; conversely, the heart rate was more elevated during the logical task. Finally, the systolic blood pressure seemed to be strongly sensitive to psychological stress. A better taking into account of the precise influence of a given cognitive activity and both workload and related task-induced psychological stress during task performance is a promising way to better monitor operators in complex working situations to detect mental overload or pejorative stress factor of error.     

Different types of circulatory responses to mental tasks

The present study investigated the circulatory responses to two mental tasks. Forty males and females performed a mental subtraction task and a color-word task. During each task, the systolic and diastolic blood pressure, mean arterial pressure, heart rate, stroke volume, cardiac output, and total peripheral resistance were measured as cardiovascular indices for a 5-min baseline, a 5-min task period, and a 10-min recovery period. As for the results, three hemodynamic reactivity patterns were verified: Pattern C, characterized by increased cardiac output and decreased total peripheral resistance; Pattern M, characterized by a moderate increase in both cardiac output and total peripheral resistance; and Pattern V, characterized by increased total peripheral resistance and decreased cardiac output. Also, four response types were found among all subjects: Type 1: cardiovascular responses showed the cardiac pattern for both tasks; Type 2: cardiovascular responses changed between the cardiac pattern and the mixed pattern with a change of tasks; Type 3: cardiovascular responses showed the mixed pattern for both tasks; Type 4: cardiovascular responses changed between the mixed pattern and the vascular pattern with a change of tasks. The comparison between types showed that Type 3 and Type 4 had an elevation in their blood pressure by an increased total peripheral resistance. On the other hand, Type 1 and Type 2 tended to have an increased blood pressure by a rise in their cardiac output. And Type 3 and Type 4 showed higher blood pressure and higher scores on the Type A behavior pattern questionnaire. In conclusion, at least four types of circulation response to the mental tasks existed, with Type 3 and Type 4 having higher blood pressure responses and tending to have an elevated blood pressure by a rise in their total peripheral resistance.     

Exposure to bright light modifies HRV responses to mental tasks during nocturnal sleep deprivation

This study was intended to determine the effects of continuous bright light exposure on cardiovascular responses, particularly heart rate variability (HRV), at rest and during performance of mental tasks with acute nocturnal sleep deprivation. Eight healthy male subjects stayed awake from 21.00 to 04.30 hours under bright (BL, 2800 lux) or dim (DL, 120 lux) light conditions. During sleep deprivation, mental tasks (Stroop color-word conflict test: CWT) were performed for 15 min each hour. Blood pressure, electrocardiogram, respiratory rate, urinary melatonin concentrations and rectal temperature were measured. During sleep deprivation, BL exposure depressed melatonin secretion in comparison to DL conditions. During sleep deprivation, exposure to BL delayed the decline in heart rate (HR) for 4 h in resting periods. A significant increment of HR induced by each CWT was detected, especially at 03.00 h and later, under DL conditions only. In addition, at 04.00 h, an index of sympathetic activity and sympatho-vagal balance on HRV during CWT increased significantly under DL conditions. In contrast, an index of parasympathetic activity during CWT decreased significantly under DL conditions. However, the indexes of HRV during CWT did not change throughout sleep deprivation under BL conditions. Our results suggest that BL exposure not only delays the nocturnal decrease in HR at rest but also maintains HR and balance of cardiac autonomic modulation to mental tasks during nocturnal sleep deprivation.     

Characteristics of the spatial organization of oscillations of brain bioelectric potentials in adolescents

Adolescence is characterized by an intense formation of interregional interaction of cortical areas. In this period, the activity of deep brain structures is significantly reorganizing and cortical-subcortical interaction is augmenting. Our objective was to assess the pattern of changes in the spatial structure of brain bioelectric potentials with age and characteristics of these structures in adolescents. For this purpose, studies of EEG were conducted in 230 subjects of both sexes aged 4 to 35 years. We quantified the interconsistent changes in correlations of oscillations of bioelectric potentials in 20-lead EEG, using the integrated index VOL. Age-related changes in the consistency of EEG correlations were analyzed both in the background state and during verbal activity (comprehension of texts in Russian and in English). Cognitive tasks were performed by subjects older than 8 years. It was discovered that spatial synchronization of EEG processes both in the background state and during cognitive tasks increased with age, but, after 20 years, the rate of changes decreases significantly. In adolescence (12–17 years), sex differences appear in the correlation of EEG processes between the left and right hemispheres in subjects performing verbal tasks. We observed saltatory changes in VOL indices in 12- to 14-year-old boys, whereas in girls of the same age, reorganization of systemic brain activity goes more gradually 1.5–2 years in advance.     

Changes in Hemodynamic Response to Mental Stress with Heart Rate Feedback Training

This study was designed to examine underlying hemodynamic changes that accompany observed reductions in heart rate (HR) response to mental stress following HR feedback training. Twenty-five college males, assigned to either a HR feedback training group (FB+) or a control group (FB–), were presented with a videogame and mental arithmetic challenge, as HR, blood pressure, and impedance cardiography-derived measures of hemodynamic functioning were recorded. During training, the FB+ group received HR feedback and the FB– group was not provided with HR feedback while playing a videogame. At posttraining, results revealed that the FB+ group exhibited significantly lower HR, systolic blood pressure, stroke volume, and total peripheral resistance responses to the videogame compared to that at pretraining. There was no evidence that the acquired skills generalized to a mental arithmetic task. These results suggest that HR feedback training is an effective method for reducing cardiovascular and hemodynamic responses to a mental stressor; however, the generalizability of this effect remains questionable.     

Reduced forearm alpha1-adrenergic vasoconstriction is associated with enhanced heart rate fluctuations in humans.

In the present study, we assessed whether heart rate (HR) or arterial pressure fluctuations are enhanced in healthy young humans with reduced alpha-adrenergic vasoconstrictor responses and, if so, whether this occurs for both alpha1- and alpha2-adrenergic receptor-mediated vasoconstriction. Arterial pressure (brachial artery catheter) and HR (ECG) were monitored continuously, and alpha1- and alpha2-adrenergic responsiveness was determined by assessing the effects of brachial artery infusions of phenylephrine (alpha1-adrenergic agonist) and dexmedetomidine (alpha2-adrenergic agonist), respectively, on forearm blood flow (strain gauge plethysmography). alpha1-Adrenergic responsiveness varied markedly among the subjects (n=20) and was inversely correlated with coefficient of variation for HR (R2=0.37, P<0.01), whereas the responsiveness was not correlated with the coefficient of variation for either systolic or diastolic arterial pressure. alpha1-Adrenergic responsiveness was inversely and more strongly correlated with baroreflex sensitivity (R2=0.62, P<0.0001), determined from beat-to-beat changes in HR and systolic arterial pressure, than the coefficient of variation for HR. On the other hand, alpha2-adrenergic responsiveness was not correlated with any of the parameters determined above. These results suggest that, in healthy young subjects, the enhanced HR response to changes in systolic pressure helps maintain the stability of arterial blood pressure when alpha1-adrenergic responsiveness is reduced.     

Assessment of human operator functional state using a novel differential evolution optimization based adaptive fuzzy model

With the development of human–machine systems, there has been a growing concern about the consequences of operator performance breakdown under excessive level of workload, especially in safety-critical situations. Assessment and detection of the operator functional state (OFS) enable us to predict the high operational risks of operator. This paper adopts the psychophysiological signals and task performance measures to evaluate OFS under different levels of mental workload. Four indices extracted from electrocardiogram and electroencephalogram, including heart rate (HR), ratio of the standard deviation to the average of HR segment, task load indices (TLI1 and TLI2), are chosen as the inputs of the proposed model. A technique of differential evolution with ant colony search (DEACS) is developed to optimize the parameters of Adaptive-Network-based Fuzzy Inference System (ANFIS). The optimized ANFIS model is employed to estimate the OFS under a series of process control tasks on a simulated software platform of AUTOmation-enhanced Cabin Air Management System. The results showed that the proposed adaptive fuzzy model based on ANFIS and DEACS algorithm is applicable for the operator functional state assessment.     

Heart Rate Variability and Blood Pressure during Dynamic and Static Exercise at Similar Heart Rate Levels

Aim was to elucidate autonomic responses to dynamic and static (isometric) exercise of the lower limbs eliciting the same moderate heart rate (HR) response. Method: 23 males performed two kinds of voluntary exercise in a supine position at similar heart rates: static exercise (SE) of the lower limbs (static leg press) and dynamic exercise (DE) of the lower limbs (cycling). Subjective effort, systolic (SBP) and diastolic blood pressure (DBP), mean arterial pressure (MAP), rate pressure product (RPP) and the time between consecutive heart beats (RR-intervals) were measured. Time-domain (SDNN, RMSSD), frequency-domain (power in the low and high frequency band (LFP, HFP)) and geometric measures (SD1, SD2) as well as non-linear measures of regularity (approximate entropy (ApEn), sample entropy (SampEn) and correlation dimension D2) were calculated. Results: Although HR was similar during both exercise conditions (88±10 bpm), subjective effort, SBP, DBP, MAP and RPP were significantly enhanced during SE. HRV indicators representing overall variability (SDNN, SD 2) and vagal modulated variability (RMSSD, HFP, SD 1) were increased. LFP, thought to be modulated by both autonomic branches, tended to be higher during SE. ApEn and SampEn were decreased whereas D₂ was enhanced during SE. It can be concluded that autonomic control processes during SE and DE were qualitatively different despite similar heart rate levels. The differences were reflected by blood pressure and HRV indices. HRV-measures indicated a stronger vagal cardiac activity during SE, while blood pressure response indicated a stronger sympathetic efferent activity to the vessels. The elevated vagal cardiac activity during SE might be a response mechanism, compensating a possible co-activation of sympathetic cardiac efferents, as HR and LF/HF was similar and LFP tended to be higher. However, this conclusion must be drawn cautiously as there is no HRV-marker reflecting “pure” sympathetic cardiac activity.     

Central hemodynamics and motor activity in 11- to 12-year-old girls under different conditions of school instruction

The left ventricular power (LVP), stroke volume (SV), cardiac output (Q), systolic blood pressure (BP_s), and the overall physical activity of schoolgirls attending gymnasium classes with in-depth instruction in specific subjects were lower than in those attending general education classes with the standard curriculum. There were no differences in heart rate (HR), specific peripheral resistance (SPR), or diastolic blood pressure. The stroke index (SI) and cardiac index (CI) were, respectively, moderately and strongly correlated with the degree of motor activity.     

Ambient temperature affects glabrous skin vasculature and sweating responses to mental task in humans

We compared responses in heart rate (HR), mean blood pressure (MAP), sweating rate (SR), sweating expulsion (SwE), and skin vascular conductance (VC) to mental task among different ambient temperature (Ta) conditions, i.e., 12, 16, 20, and 24 degrees C. Seven subjects (27+/-5 yrs, 64+/-14 kg) underwent a 2-min color word conflict test (CWT) after 2 mins of baseline data acquisition following a 20-min resting period. All subjects wore long sleeve shirts and long pants. The skin blood flow was measured with a laser Doppler probe on the left index finger pulp to calculate skin VC, and the SR and sweating expulsion (SwE) were measured with a ventilated capsule on the left thenar. CWT significantly increased the HR and MAP, while there was no significant effect of Ta on the magnitudes of these responses. CWT significantly decreased the skin VC when the Ta was 24 degrees C, whereas it significantly increased the skin VC when the Ta was 12 or 16 degrees C. CWT significantly increased SR and SwE in all Ta conditions, and the SwE was greater in warmer conditions. These findings suggest that different ambient temperatures induce different responses in finger skin vasculature to mental task, implying the independent response of cutaneous vasomotor tone and sweat glands in glabrous skin to mental task.     

Circadian Rhythm of Blood Pressure and Heart Rate in Healthy Persons and Kidney Transplant Patients: Correlations with Activity

Fourteen diurnally active (07: 00–22: 39 h) normotensive healthy control subjects and 14 kidney transplant patients were studied by ambulatory blood pressure monitoring and wrist actigraphy simultaneously during one 24-h period. In the control group, circadian rhythms in systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressure, heart rate (HR), and wrist activity were documented by cosinor analysis with comparable afternoon peak times. In contrast, circadian rhythms with afternoon acrophases were detected only in HR and wrist activity in the patient group. The correlation of wrist activity with HR in controls and patients was comparable. Wrist activity and blood pressure were associated (r = 0.65 DBP and 0.54 SBP; p < 0.05) in controls, while in patients the relationship was weak or absent (r ranging from 0.02 SBP to 0.22 DBP). In 6 of 14 patients, BP and wrist activity were negatively correlated, reflecting the existence of nocturnal hypertension. In eight others, the correlation was small but positive. The 24-h pattern in BP and wrist activity in controls was comparably phased; however, this was not the case for the transplant patients, indicating the day-night pattern in blood pressure in this group is strongly dependent on pathologic phenomena rather than activity level and pattern.     

An approach to remote monitoring of heart rate variability (HRV) using microwave radar during a calculation task

Recently, nonrestrictive and noninvasive sensing techniques to measure vital signs have been actively researched and developed. This study aimed to develop a prototype system to monitor cardiac activity using microwave radar without making contact with the body and without removing clothing--namely, a completely noncontact, remote monitoring system. In addition, heart rate and changes in heart rate variability (HRV) during simple mental arithmetic tasks were observed with the prototype system. The prototype system has a microwave Doppler radar antenna with 24 GHz frequency and approximately 7 mW output power. The experiments were conducted with seven subjects (23.00±0.82 years). We found that the prototype system captured heart rate and HRV precisely. The strong relationship between the heart rates during tasks (r=0.96), LF (cross-correlation=0.76), and LF/HF (cross-correlation=0.73) of HRV calculated from the prototype system and from electrocardiograph (ECG) measurements were confirmed. The proposed completely noncontact, remote method appears promising for future monitoring of cardiac activity as an indicator of changes in mental workload in workplaces.     

Baroreceptor reflex and arterial rigidity in schoolchildren

In this work there is shown a variability of heart rate and time delay of pulse wave of main arteries in schoolchildren.There is used the function of ordinary coherence of HR and DPW (time delay of pulse wave). This function reflects the rate of statistical linear relation of two processes in heart and blood vessels. A high tone of sympathetic part of vegetative nervous activity in schoolchildren increases CO (cardeiac out), shortens the hard connection phase of HR and DPW and results in a new system characteristic--arterial rigidity. There are presented results of passive orthostatic test and pharmacological tests on activation of sympathetic part of vegetative nervous activity in schoolchildren with heart rate problems.     

Role of cognitive and personality variables in regulation of heart rhythm

The heart rate (HR) response to stimulation is described as a biphasic function with a phase of deceleration and acceleration. The deceleration is interpreted as a component of orienting behavior or of stimulus intake and acceleration as a sign of internal information processing going along with the rejection of external stimulation. However, there are many authors who do not support this assumption. The question arises whether the heart rate patterns are concomitant or even dependent on breathing behavior. Also the sensitivity of HR as an indicator of influence of selfregulatory processes on physiological functions remains still a problem for future studies. In general it may be concluded that the HR is one of the relatively independent indices of changes in the level of activation or mobilization. The HR in healthy subjects is a function not only of intensity and modality of the stimulus but also of prestimulus level of activation and its dependence on breathing behavior. At the same time there is evidence of a connection of HR with high cognitive processes which in an interaction of the organism and environment together with volitional processes have a regulatory function.     

Variations in blood pressure and heart rate in conscious rats with cervical lymphatic blockade

The possible effects of cervical lymphatic blockade (CLB) on a series of parameters in conscious freely moving rats were analysed. Blood pressure (BP) and heart rate (HR) for conscious male Sprague-Dawley rats at 1, 3, 7, 11, 15 and 21 days after a CLB or a sham operation were monitored continuously for 24 hours with a computerized recording system. Since BP and HR were subjected to spontaneous variations, blood pressure variability (BPV) and heart rate variability (HRV) were expressed as the standard deviation of beat-to-beat BP and HR values. The baroreflex sensitivities (BRS) were determined by measuring the heart period (HP = 60,000/HR) prolongation in response to the elevation in BP induced by an intravenous administration of phenylephrine at 1, 7, 15 and 21 days after the CLB or sham operation. Compared with those in sham-operated rats, the values of systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), HR and BRS in CLB rats were significantly lower, whereas the values of BPV and HRV were markedly raised in CLB rats at different time points. Furthermore, the impaired ultrastructure in the dorsomedial nucleus of the solitary tract (dmNTS) including degeneration, apoptosis and necrosis in neurons and gliacytes, were apparent from the 1st to 15th day but the changes were most significant at 7th day after CLB operation. Structural changes appeared to be closely related to functional changes of the dmNTS at each time point. Thus, in CLB conscious rats, a significant decline in blood pressure accompanied by dysfunction in its regulation might be due to the impaired structure in the dmNTS.     

Functional capacity of the cardiovascular system of elderly people as estimated by heart rate variability

With the aid of mathematical and spectral analysis of the heart rate (HR) wave structure in a dynamic interval tachogram (TG) in elderly subjects, it has been shown that a stable sinus rhythm is typical of the majority of the indigenous population of the rural areas of the North aged 78–97 years and migrants living in the city of Vorkuta aged 60–88 years. The total RR-interval spectrum power (800 ± 98 ms²) in the TGs of the native population is shifted to the very low frequency band (VLF, 52%), which indicates predomination of the humoral-metabolic HR regulation level. The reaction to orthostatic load in elderly subjects is characterized by a significant increase in the total spectrum power, which indicates changes in the autonomic balance of regulation of the wave structure of the HR variability. A low total spectrum power (609 ± 104 ms²) with a predominance of low frequency (LF) waves in the TGs of the migrants at rest reflects the activity of the sympathetic component of HR regulation. The reduction of the parasympathetic regulation and the growth of the sympathetic activity during an active orthostatic test in the migrants is a predictor of cardiovascular diseases. In individual TGs of recipients with HR disorders, the orthostatic test (the redistribution of blood flow in the main vessels) results in a decrease in the number of extrasystoles due to the specific features of the baroreflex regulation mechanisms of the cardiovascular system. The HR variability has been shown to be an indicator of the functional capacity of the cardiovascular system in elderly subjects.     

The influence of endurance training on the transient haemodynamic response to orthostatic manoeuvre.

Several investigations demonstrated that aerobic fitness is associated with a tendency towards orthostatic hypotension whereas other reports did not show any differences in cardiovascular adjustment to orthostatic challenges between endurance trained and sedentary subjects. In the present work, the time course of changes in heart rate (HR), systolic time intervals (STI), stroke volume (SV), cardiac output (CO) and blood pressure was studied during 8 minutes following standing up from supine position in 7 healthy volunteers before and after 10 weeks of endurance training on bicycle ergometer. Impedance cardiography was used for measurement of cardiac postural responses. The training program applied in this study increased the subjects' aerobic capacity (VO2max) by approx. 18%. After training, the steady-state supine HR and contribution of the pre-ejection period and ejection time to the total R-R interval in ECG were lowered while SV was significantly increased. No significant training-induced changes were found in magnitude and time-courses of HR, STI, SV and CO changes following standing up. Diastolic blood pressure during standing was greater after than before training. It is concluded that the short-time endurance training does not affect adversely cardiovascular orthostatic response and may even improve orthostatic tolerance due to the augmentation of diastolic blood pressure response.     

Heterogeneity of psychophysiological stress responses in fibromyalgia syndrome patients

Dysregulated psychophysiological responses have been observed in patients with fibromyalgia syndrome (FMS), although the results are inconsistent. Surface electromyographic (EMG), systolic and diastolic blood pressure, heart rate (HR), and skin conductance levels (SCLs) were continuously recorded at baseline, and during a series of stress and relaxation tasks in 90 FMS patients and 30 age and sex matched healthy controls (HCs). The patient sample demonstrated lower baseline EMG levels compared to the HCs on all tasks. In contrast, the patients displayed elevated HR and SCL (sympathetic vasomotor and sudomotor indices, respectively) during both stress tasks. A cluster analysis identified four psychophysiological response patterns: 63.3% of HCs showed increased muscle tension and stable cardiovascular responses; 34.8% of FMS patients showed a pattern of increased sympathetic vasomotor reactivity with stable sudomotor and reduced muscular response; 12.2% of FMS patients showed a pattern of increased sympathetic sudomotor reactivity connected with increased sympathetic vasomotor response and reduced muscular response; and, in contrast, 46.7% of FMS patients showed a pattern of parasympathetic vasomotor reactivity and reduced sudomotor as well as muscular response. The identification of low baseline muscle tension in FMS is discrepant with other chronic pain syndromes and suggests that unique psychophysiological features may be associated with FMS. The different psychophysiological response patterns within the patient sample support the heterogeneity of FMS.