Tonic blood pressure modulates the relationship between baroreceptor cardiac reflex sensitivity and cognitive performance

This study explored the effects of tonic blood pressure on the association between baroreceptor cardiac reflex sensitivity and cognitive performance. Sixty female participants completed a mental arithmetic task. Baroreceptor reflex sensitivity was assessed using sequence analysis. An interaction was found, indicating that the relationship between baroreceptor reflex sensitivity and cognitive performance is modulated by blood pressure levels. Reflex sensitivity was inversely associated to performance indices in the subgroup of participants with systolic blood pressure above the mean, whereas the association was positive in participants with systolic values below the mean. These results are in accordance with the findings in the field of pain perception and suggest that tonic blood pressure modulates the inhibitory effects of baroreceptor stimulation on high central nervous functions.     

Relationship between baroreceptor cardiac reflex sensitivity and pain experience in normotensive individuals.

In the present study, the relationship between cardiac baroreceptor function and the perception of acute pain was investigated in 60 normotensive subjects. Baroreceptor reflex sensitivity was determined using the sequence method based on continuous blood pressure recordings. A cold pressor test was used for pain induction. Visual analogue scales and a questionnaire were applied in order to quantify sensory and affective pain experience. Moderated multiple regression analysis revealed an inverse relationship between baroreceptor reflex sensitivity assessed during painful stimulation and the intensity of experienced pain. This relationship was moderated by resting blood pressure, with decreasing blood pressure being accompanied by a decrease in the magnitude of the association. Furthermore, resting blood pressure was inversely related to pain intensity. The inverse association between baroreceptor reflex sensitivity and pain experience is discussed as reflecting the well-established pain-inhibiting effect of baroreceptor activity. The finding that this relationship was less pronounced in the case of lower blood pressure suggests that baroreceptor-mediated pain attenuation is reduced in this population.     

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.     

Relationships between baroreceptor cardiac reflex sensitivity and cognitive performance: modulations by gender and blood pressure

This study aimed at replicating and extending previous results on the association between baroreceptor reflex sensitivity (BRS) and cognitive performance. Thirty men and 31 women performed an arithmetic task. After adjusting for numerical aptitude and effort, no predictors of performance were found in men. In women, the relationships between BRS and parameters related to correct responses were modulated by blood pressure (BP). BRS was inversely associated with these parameters for participants with BP>1 SD above the mean, whereas the associations were positive in participants with BP<1 SD below the mean. Also for women, BRS was positively associated with number of errors during the task. These results suggest that the relation between BRS and performance varies as a function of the type of cognitive processes assessed and that the central nervous system effects of the baroreceptors on cognitive functioning are modulated by gender and BP.     

Effects of spaceflight on postnatal development of arterial baroreceptor reflex in rats

AIM: It has been reported that spaceflight attenuates the arterial baroreceptor reflex. As this reflex function changes dramatically during postnatal development, we hypothesized that space flight depresses the developmental changes of the reflex system. To test this hypothesis, we evaluated the baroreceptor reflex function in rats, which were exposed to a microgravity environment on a space shuttle 9-25 days after birth. METHODS: Baroreceptor reflex sensitivity and the afferent sensitivity were evaluated by measuring heart rate (HR) and aortic nerve activity (ANA) changes in response to an increase in mean arterial pressure (MBP) derived by phenylephrine injection (20-50 microg kg(-1)) under urethane-anaesthesia. RESULTS: Baroreceptor reflex sensitivity (% change of HR/% change of MBP) was lower in the flight group (FLT: -0.19 +/- 0.04, n = 4) than either the asynchronous ground control group (AGC: -0.47 +/- 0.06, n = 6, P < 0.01) or the vivarium group (VIV: -0.41 +/- 0.07, n = 6, P < 0.05). This was similar to the differences of the afferent sensitivity (% change of ANA/% change of MBP) between FLT (2.07 +/- 0.30) and the control groups (AGC: 2.71 +/- 0.22, n.s.; VIV: 3.00 +/- 0.32, P < 0.05). At the end of 30 days of recovery under normal gravity conditions, however, there were no significant group differences in these parameters. conclusion: These results suggest that the space environment attenuates the postnatal development of the arterial baroreceptor reflex function in rats, which may be partially because of a depression of the postnatal development of the baroreceptor afferents. These functional alterations, however, recover to their normal level on re-exposure to the Earth's gravity.     

Baroreceptor sensitivity and effectiveness varies differentially as a function of cognitive-attentional demands

From the spontaneous sequence method, a new index of baroreceptor function has recently been proposed, the baroreflex effectiveness index (BEI). BEI quantifies the number of times the baroreflex is effective in driving the sinus node. In this study we examined how different cognitive-attentional demands modulates BEI and baroreceptor reflex sensitivity (BRS). Eighty three students performed three tasks: mental arithmetic, memory, and visual attention. Results indicate that BRS reliably decreases during mental arithmetic and increases slightly during visual attention. BEI increases during the visual attention task. The overall pressure change of the systolic blood pressure ramps decreases during tasks with respect to baseline periods and cannot explain the effect found in BEI (in effect, BEI works against this underlining influence). The modulation found in BRS and BEI as a function of cognitive demand is in accordance with the Laceys' intake/rejection theory. Specifically, it is suggested that BRS is more sensitive to internal cognitive elaboration conditions, while BEI is more sensitive to external attention conditions.     

内田-克莱佩林测验在民航飞行学员选拔中的应用

目的 :探讨内田 -克莱佩林测验结果与飞行学员工作绩效、情绪稳定性的关系。方法 :根据内田 -克莱佩林测验成绩将 3 5 3名飞行学员分组 ,采用访谈法和艾森克人格测验对 3 5 3名飞行学员的情绪稳定性进行评估 ,比较不同组在理论学习成绩、招飞成绩、飞行成绩和情绪稳定性上的差别。结果 :根据能力和偏差指数将被试分为 3组 ,能力指数高、偏差指数低组在飞行成绩 (t=2 2 3 ,P <0 0 5 )比能力指数低、偏差指数高组且差异有显著性 ;情绪稳定性 (他评 )在兴奋性的不同水平有显著差异 ,兴奋水平适度的情绪稳定性最好 ,招飞测验成绩在不同可变性水平有显著差异 ,飞行成绩在启动性的过度与不足 (t =2 2 7,P <0 0 5 )及适度和不足间有差异 (t =2 12 ,P <0 0 5 )启动性不足的飞行成绩最差 ,而可变性过度的招飞成绩最好 ,理论学习成绩仅具有上述三个神经类型的二阶交互作用。结论 :内田 -克莱佩林测验在飞行学员选拔上有一定的应用价值。     

Carotid baroreflex sensitivity at rest and during psychological stress in offspring of hypertensives and non-twin sibling pairs

The baroreceptor reflexes of 38 young adult males were mechanically stimulated by negative external cervical pressure during a mental arithmetic task and pre-stress and post-stress relaxation periods. The subjects comprised 19 pairs of non-twin siblings. Baroreflex sensitivity was significantly less pronounced during arithmetic. Using non-invasive techniques, this finding replicates several others indicating a damping of the baroreceptor reflux during stress. More importantly, analyses of sibling similarities also revealed significant familiality of baroreflex sensitivity, independent of age, body mass, pressure applied and baseline heart rate. To examine the relationship between baroreflex sensitivity and parental history of hypertension, 21 young adult males with a parental history and 25 without participated in a second experiment. The two groups were not significantly different in resting baroreflex sensitivity. However, sensitivity was damped to a significantly greater degree during mental arithmetic in offspring of hypertensives, offering one possible explanation for their greater blood pressure reactivity to stress. These results suggest that familial influences may effect baroreflex sensitivity and, possibly as a result, blood pressure reactivity and risk for hypertension.     

Baroreflex control of the circulation in patients with congestive heart failure

Vagal and glossopharyngeal afferents from cardiopulmonary and arterial baroreceptors exert supraspinal tonic restraint on sympathetic efferent outflow. The baroreceptor inhibitory influence is directly related to physiological changes in cardiac filling and arterial pressures. Increased cardiac pressures and dimensions during CHF may provide chronic stimulation that reduces responsiveness of these receptors and thereby influence the neurohumoral control of the circulation. Patients with chronic and severe CHF of ischemic cause were compared with control subjects whose ischemic heart disease did not affect cardiac performance. Orthostatic pooling of blood with use of upright tilt (45 degree), provided an apparently sufficient stimulus to unload baroreceptors in patients like controls. In contrast to peripheral vasoconstriction in controls, the patients dilated their resistance vessels during upright tilt. This abnormal vasodilation was systemic and uniform in skeletal muscle and subcutaneous tissue of the forearm remaining at heart level. Such an inability to vasoconstrict in the patients, could not be attributed to depression of local vasoconstrictor reflex or autoregulatory responsiveness of forearm vascular beds. Neural blockade carried out separately or in combination with blockades of forearm vascular effector receptors revealed; increased neural efferent activity to the forearm during tilting the patients which mediated beta-adrenergic vasodilation in both vascular beds. The patients had augmented circulating catecholamine levels, those for epinephrine increased in venous effluents but were maintained in brachial arterial inflow, and those for norepinephrine increased in arterial rather than venous plasma in the forearm. Following the patients during a course of therapy with a selective vasodilator calcium antagonist, the beta-adrenergic reflex vasodilation became substantially attenuated but was preserved during a placebo course of therapy. The beta-adrenergic reflex effect evidenced in the studied patients is most probably a manifestation of reduced baroreceptor afferent restraint and it could subsequently relate to the severity of depression of baroreceptor sensitivity during the course of CHF.     

Differentiated Interaction between the Hypothalamic Defence Area and Baroreceptor Reflexes

In experiments on cats, the interaction between the oppositely directed hypothalamic defence reaction and the baroreceptor reflexes was analysed with particular regard to the effects on aortic blood flow, left ventricular work load and muscle blood flow. Because of their differentiated interaction — suppression of the baroreceptor reflex effect on the heart with preservation of the reflex modulation of the vascular bed (Djojosugito et al. 1969) — the baroreceptor reflex so modifies the primary defence reaction, with its intense neurogenic drive on the heart, that a greater cardiac output is gained for a given left ventricular work load. This particularly favours muscle blood supply. It follows that such a differentiated interaction between two basically opposite autonomic patterns causes them to act in synergism with respect to efficient cardiovascular performance in states of emergency.     

The cause of the difference between the arterial baroreceptor reflex under natural pulsatile circulation and under nonpulsatile systemic circulation

In a previous study we investigated the relation between afferent and efferent activity of the arterial baroreceptor reflex under nonpulsatile systemic circulation using total left heart bypass. The results indicated that the regulation of the arterial baroreceptor reflex was converted under nonpulsatile systemic circulation, and we inferred that a possible reason for this conversion was the transformation in discharge of the afferent activity of the arterial baroreceptor reflex that took place under nonpulsatile systemic circulation. In the present study we tested this hypothesis by sectioning carotid sinus and aortic depressor nerves and electrically stimulating bilateral aortic depressor nerves under anesthesia in five rabbits (400 spikes for 20s, with 0.02ms pulse width and 8 V amplitude), while recording changes in aortic pressure, mean aortic pressure, and heart rate. Continuous stimulation was taken as discharge of the afferent activity of the arterial baroreceptor reflex under nonpulsatile systemic circulation, and periodic stimulation was taken as discharge under natural pulsatile circulation. Aortic pressure, mean aortic pressure, and heart rate decreased under both continous and periodic stimulation. The decreases in mean aortic pressure and heart rate during continuous stimulation were significantly lower than those during periodic stimulation. Our results suggest that the transformation in discharge of the afferent activity of the arterial baroreceptor reflex under nonpulsatile systemic circulation may have played an important causative role in the conversion of the regulation of the arterial baroreceptor reflex under nonpulsatile systemic circulation.     

Carotid baroreceptor reflexes in humans during orthostatic stress

Orthostatic stress, including standing, head-up tilting and lower body suction, results in increases in peripheral vascular resistance but little or no change in mean arterial pressure. This study was undertaken to determine whether the sensitivity of the carotid baroreceptor reflex was enhanced during conditions of decreased venous return. We studied eight healthy subjects and determined responses of pulse interval (ECG) and forearm vascular resistance (mean finger blood pressure divided by Doppler estimate of brachial artery blood velocity) to graded increases and decreases in carotid transmural pressure, effected by a neck suction/pressure device. Responses were determined with and without the application of lower body negative pressure (LBNP) at -40 mmHg. Stimulus-response curves were determined as the responses to graded neck pressure changes and the differential of this provided estimates of reflex sensitivity. Changes in carotid transmural pressure caused graded changes in R-R interval and vascular resistance. The cardiac responses were unaffected by LBNP. Vascular resistance responses, however, were significantly enhanced during LBNP and the peak gain of the reflex was increased from 1.2 +/- 0.3 (mean +/- S.E.M.) to 2.2 +/- 0.3 units (P < 0.05). The increased baroreflex gain may contribute to maintenance of blood pressure during orthostatic stress and limit the pressure decreases during prolonged periods of such stress.     

Functional changes in autonomic nervous system and baroreceptor reflex induced by 14 days of 6° head-down bed rest

We studied the effects of 14 days of 6° head-down bed rest (HDBR) in 16 healthy male subjects to examine the functional changes in the autonomic nervous system and cardiac baroreceptor reflex response with an emphasis on dynamic changes during HDBR. Beat-by-beat RR intervals (RRIs) and systolic arterial pressures (SAPs) were measured non-invasively from simultaneous, continuous recordings of ECG and arterial pressure waves in supine resting postures. A power spectrum analysis by the fast Fourier transform was applied to a data set composed of interpolated 512 RRIs and 512 SAPs (256 s in duration). Three indices of cardiac baroreceptor reflex sensitivity (BRS) were obtained by applying a sequence technique and a cross-spectrum analysis technique to the spontaneous RRIs and SAPs. The high-frequency band power of RRI variability (HF_RRI) decreased significantly in the latter part of HDBR and persisted until the initial stage of the post-HDBR period (POST). The low-frequency band power of SAP variability decreased significantly only during the mid-part of HDBR. The BRS_sequence obtained by the sequence technique showed a significant increase temporarily on the initial day of HDBR. The BRS_sequence and the estimate of BRS obtained by the cross-spectrum analysis handling the high-frequency band were both significantly decreased on the initial day of POST. Each of the BRS estimates correlated negatively with heart rate and positively with HF_RRI during HDBR and POST. These results suggest the following: (1) cardiac spontaneous baroreceptor reflex sensitivity might be transiently increased at the initial stage of HDBR, (2) the reduction in vagal modulation on the sinus node occurs from the latter part of HDBR to the initial stage of POST, (3) sympathetic vasomotor control is probably slightly inhibited during the mid-part of HDBR, and (4) the enhancement in cardiac sympathetic modulation and the impairment in cardiac spontaneous baroreceptor reflex sensitivity may occur in the initial stage of POST.     

Concentration on a task and change in pulse rate and finger skin blood flow (author's transl)

Eight subjects were given a pursuit tracking task (Exp. I), a continuous task involving the adding of digits (Exp. II), and the Uchida-Kraepelin psychodiagnostic test (Exp. III). Experiments I and II employed distributed practice. Finger Skin Blood Flow (SBF) and Pulse Rate (PR) were measured during the experiments. It was found that SBF was smaller during trials than during intertrial rests, the latter being smaller than rests with eyes closed. SBF was smallest during the first trial (Exp. I & II) or the first minute (Exp. III). PR reversed direction with some differences being observed between the changes in PR and SBF. The results indicate that concentration on a task is reflected better by SBF than by PR.     

Baroreceptor sensitivity in two-week-old rat pups: effects of nutrient deprivation and sino-aortic denervation

Resting cardiac rates are reduced 40% by nutrient deprivation in two-week-old rats while arterial pressure is maintained at stable levels. Previous evidence implicated arterial baroreceptors and suggested the hypothesis that the cardiac rate changes result from increased baroreceptor sensitivity following nutrient deprivation. In order to test this hypothesis, cardiac reflex responses were elicited by graded doses of phenylephrine and sodium nitroprusside before and after nutrient deprivation. Although cardiac rate decelerations in response to phenylephrine were greater in fed pups (p less than 0.05) and acceleration in response to nitroprusside were greater in the deprived condition (p less than 0.01), these could be attributed to 'ceiling' and 'floor' effects of the resting cardiac rates characteristic of the two nutrient conditions. Sino-aortic denervation eliminated cardiac reflex responses, substantiating their dependence on baroreceptor afferents. Regression analysis of cardiac reflex responses to arterial pressure changes failed to show changes in baroreceptor sensitivity that would support the hypothesis. Alternate mechanisms mediating the nutrient effect on cardiac rate (e.g., involving neural and peptide hormonal pathways) should be pursued.     

Baroreceptor and chemoreceptor influences on heart rate during the respiratory cycle in the dog.

1. Brief stimuli were delivered to the carotid chemoreceptors or baroreceptors in dogs anaesthetized with pentobarbitone or chloralose. Chemoreceptor stimulation was achieved by rapid retrograde injections of 0-2-0-5 ml. warmed, CO2-equilibrated saline through a cannula in the external carotid artery. Baroreceptor stimulation was achieved by forceful retrograde injection of 2-5 ml. air-equilibrated saline, or of freshly drawn arterial blood, into the external carotid artery after first clamping the common carotid artery. 2. Brief baroreceptor stimuli had no noticeable effect on breathing. Brief chemoreceptor stimuli had no effect on breathing in some dogs, but in many produced a reflex increase in the depth of inspiration when delivered during inspiration. In these same dogs, brief chemoreceptor stimuli delivered in expiration either prolonged the expiratory pause or evoked an active expiratory effort. 3. Prompt decreases in heart rate were elicited by brief sudden chemoreceptor or baroreceptor stimuli when these were delivered during the expiratory phase of respiration. The stimuli did not modify the control heart rate pattern when delivered during inspiration. If the carotid sinus nerve or the vagus nerves were cut the responses were abolished. 4. Brief chemoreceptor or baroreceptor stimuli remained effective in evoking prompt decreases in heart rate during periods of apnoea in the end-inspiratory position (Hering-Breuer inflation reflex). In periods of apnoea after prolonged artificial hyperventilation the stimuli were sometimes ineffective at first, but were always effective late in the period of apnoea, again producing prompt cardiac slowing. 5. After denervation of the lungs, brief baroreceptor and chemoreceptor stimuli continued to evoke prompt falls in heart rate when given during expiration. When delivered during inspiration the same stimuli were either ineffective, or less effective.     

Modulation of reflex responses in hand muscles during rhythmical finger tasks in a subject with writer’s cramp

The objective of this study was to examine phase- and task-dependent modulation of stretch reflexes during repetitive finger movements in writer’s cramp, and compare them with normal controls from our previous study. A subject with writer’s cramp conducted two rhythmic tasks, index finger abduction (RFA) and a pen-squeezing (RPS) task akin to handwriting. Stretch reflexes were evoked by mechanical perturbations at random phases of each task. Surface electromyograms (EMG) were recorded from two hand muscles, first dorsal interosseous (FDI) and flexor digitorum superficialis (FDS). The reflex response and background EMG activity of each muscle were modulated in a phase-dependent manner in both tasks. However, they varied largely in phase during the RFA task, but in approximately inverse phase-relationship during RPS. Reflex sensitivity, as represented by the slope of the linear regression between response and background, was much lower for both muscles in the ‘writing’ task (RPS) than in the RFA task with its positively correlated responses. These phase- and task-related modulation patterns differed dramatically from those observed in our control subjects, where reflex responses were modulated largely in phase with background activity and reflex sensitivity was much higher, particularly in FDI during RFA and FDS during RPS. The altered reflex modulation patterns in writer’s cramp may reflect deficiencies of integration of proprioceptive afferent inputs and reduced inhibition at cortical and spinal levels during writing performance. Results from this case study support clinically identified task-specific feature of focal hand dystonia.     

Chronic inhibition of standing behaviour alters baroreceptor reflex function in rats

Aim: To investigate whether daily orthostatic stress during development is an important factor affecting arterial baroreceptor reflex function, we examined the effect of chronic inhibition of upright standing behaviour on the baroreceptor reflex function in rats. Methods: Upright standing behaviour was chronically inhibited during the developmental period between 3 and 8 weeks of age in Sprague–Dawley rats and heart rate (HR) and aortic nerve activity in response to increased and decreased mean arterial pressure (MAP) was measured after the treatment period. Results: The baroreceptor cardiac gain in the rats grown without standing behaviour was significantly lower than the control rats grown in a normal commercial cage (1.0 ± 0.1 beats min^?1 mmHg^?1 vs. 1.6 ± 0.2 beatsmin^?1 mmHg^?1, P < 0.05). The range of HR change in the MAP–HR functional curve was also lowered by chronic inhibition of orthostatic behaviour (56.2 ± 5.9 beats min^?1) compared with that of the control rats (76.8 ± 6.9 beats min^?1, P < 0.05). However the aortic afferent function remained normal after the treatment period, indicating that the attenuated baroreceptor reflex function may be due to other mechanisms involving functional alterations in the cardiovascular centres, efferents and/or peripheral organs. Body weight and adrenal weight were not affected by the inhibition of orthostatic behaviour, suggesting that the animals were not exposed to specific stress by this treatment. Conclusion: These results indicate that active haemodynamic changes induced by orthostatic behaviour are an important factor for setting the basal level of reflex function during development. Moreover, our experimental model may be useful for studying mechanisms of attenuated baroreceptor reflex observed after exposure to a chronic inactive condition.     

The behavioral impact of baroreflex function: A review

The baroreflex consists of a negative feedback loop adjusting heart activity to blood pressure fluctuations. This review is concerned with interactions between baroreflex function and behavior. In addition to changes in baroreflex cardiac control subject to behavioral manipulations, interindividual differences in reflex function predicted psychological and central nervous features. The sensitivity of the reflex was inversely related to cognitive performance, evoked potential amplitudes, experimental pain sensitivity, and the severity of clinical pain. Possible variables moderating the strength of the associations are tonic blood pressure, gender, and psychiatric disease. It is suggested that these observations reflect inhibition of higher brain function by baroreceptor afferents. While in many cases increased baroreflex function implies stronger inhibition, individual and situational factors modulate the behavioral impact of cardiac regulation.