Effects of reward and methylphenidate on heart rate response morphology of augmenting and reducing children

In a group of attention and/or learning disordered children referred for a trial on methylphenidate, beat-to-beat analysis of heart rate (HR) to auditory stimuli showed the response to be affected by stimulus intensity, reward level, and drug condition (placebo or active). When the children were classified as augmenters or reducers on the basis of their event-related potentials to the 4 intensity levels, the reducers had significantly higher pretreatment HR response levels as well as quicker latencies to reach deceleration trough (anticipatory component) and acceleratory peak (rebound rise to the tones). The clinically titrated methylphenidate dosage levels for the subjects were related both to the augmenter-reducer classification and to pretreatment HR levels; that is, subjects who were ERP reducers and/or had higher HR levels, especially under reward conditions, were blindly titrated at higher levels than those who were augmenters and/or had lower HR levels.     

Cardiovascular and Electrodermal Response Patterns in Heart Rate Reactive Individuals During Psychological Stress

The goal of this research was to examine the cardiovascular and electrodermal response patterns of heart rate reactive and nonreactive individuals to psychological stress. Sixty males were tested while resting, listening to tones, identifying tone patterns, and performing mental arithmetic. Dependent variables were blood pressure, heart rate (HR), and skin conductance responses. Based on the change in HR from baseline to the first minute of mental arithmetic, two extreme reactivity groups of 15 subjects each were formed. Results indicated that HR reactive subjects had higher systolic blood pressure and HR than nonreactives. Reactives showed greater HR lability during all the tasks and a phasic acceleration to tones, while nonreactives showed a deceleration. Finally, comparisons of skin conductance responses indicated that subjects who were nonreactive when measuring HR were more reactive when measuring skin conductance. The HR reactivity seen in these subjects has been linked to predisposition to psychosomatic illness, and the current findings are discussed in that light.     

Heart rate discrimination and heart rate control: a test of Brener's theory

Three experiments were conducted to examine predictions from Brener's theory regarding the relationship between autonomic discrimination and autonomic control. Experiment 1 examined the possibility that training subjects to discriminate their heart rates would enhance their skill at controlling that response. Twenty subjects participated in two sessions during which one group of 10 subjects received training (knowledge of results) on the Ashton discrimination technique. The second group performed the discrimination task but received no training. All subjects then took part in a third session of heart rate (HR) control (both increase and decrease) where half of each of the aforementioned groups received feedback during the control task, while the other half performed the HR control task without feedback. Results indicated that for the control of both HR increases and decreases, there was no significant difference between those subjects trained to discriminate their HR, and those who had received no training to discriminate HR. The second experiment investigated the hypothesis that training subjects with feedback to control their HR would enhance their capacity to discriminate their heart activity. Ten subjects participated in two sessions of HR control during which half the subjects received feedback training to increase HR. During a third session, all subjects underwent a test of discrimination ability using the Ashton technique, and no knowledge of results regarding performance was provided. Results confirmed the hypothesis. The final experiment in the series investigated the discrimination/control relationship within a problem-solving framework and used 20 subjects. Results confirmed the hypothesis that subjects forewarned at the time of discrimination training that a heart rate control task was to follow would perform better than 10 subjects receiving no forewarning of the task objective. This effect took place independently of cardiac discrimination ability. A second finding from this experiment was that subjects trained to discriminate heart rate were better able to increase heart rate than untrained subjects. This result contradicts that of Experiment 1, and reasons for this anomaly are discussed in detail.     

Physiological response to a minimal social encounter: Effects of gender, ethnicity, and social context

This study examined physiological response to an encounter with and touch by an unfamiliar person. Fifty-five African American (23 male, 30 female) and 51 European American (23 male, 28 female) undergraduates participated. A Black or White interactor entered the room, introduced himself or herself, checked equipment for 30 s, and then took a pulse for 30 s. Entry of the interactor resulted in increased corrugator and zygomaticus facial muscle activity (EMG), increased skin conductance (SC), and heart rate (HR) acceleration. Corrugator EMG was greater among Black subjects; White subjects responded with more zygomatic EMG and SC and greater HR acceleration. Women showed a more positive facial expression than did men. Being touched reduced EMG and HR but resulted in increased SC. White and Black males showed more HR acceleration when encountering a Black male interactor.     

Facial reactions to fear-relevant and fear-irrelevant stimuli

Earlier research has shown that subjects exposed to different facial expressions react spontaneously with different facial electromyographic (EMG) response patterns. In the present study subjects were exposed to fear-relevant (snakes/spiders) and fear-irrelevant (flowers/mushrooms) stimuli, while facial EMG activity, skin conductance responses (SCRs) and heart rate (HR) were measured. The stimuli evoked different response patterns. Fear-relevant stimuli elicited increased corrugator muscle activity, whereas fear-irrelevant stimuli evoked increased zygomatic muscle activity. Fear-relevant stimuli also evoked HR deceleration and larger SCR magnitudes. The present data are consistent with the theory that the face constitutes an emotional 'readout/output-system'.     

Involvement of the autonomic nervous system in motor adaptation: acceleration or error reduction?

In the last few decades motor adaptation was extensively studied observing the invariant features of reaching movements. In a parallel neurobehavioral line of research emotional learning was studied under the umbrella of the ‘two-factor theory of learning’. In this study we explore the relation between motor learning and the autonomic response (heart rate, HR) of subjects performing point to point reaching movements holding a computer mouse. We consider two alternative outcomes: one is that autonomic response correlates with the learning rate and the second is that the autonomic response correlates with the residual error at the steady state. Eighteen subjects performed reaching movements under perturbed visual feedback demonstrating learning and after effects of learning. The hand movement as well as an Electrocardiogram signal were recorded throughout the training and carefully analyzed offline to extract the trial by trial error as well as the heart period. The results show clear correlation between the change in HR and the residual error but no correlation between the change in HR and the learning rate supporting the second alternative that the sensitivity to errors but not the learning rate correlates with the autonomic response. A control group of another seven subjects underwent the same experiment without the perturbed visual feedback. This control group showed no change in the HR. Further studies are required to validate this hypothesis and unravel the mechanism by which the autonomic response correlates with the residual motor error.     

Maternal stress responses and anxiety during pregnancy: effects on fetal heart rate

This study examined the effect of an acute maternal stress response and anxiety on fetal heart rate. Seventeen healthy, 3rd-trimester pregnant women (mean age = 26 +/- 6 years) were instrumented for continuous electrocardiography, blood pressure (BP), respiration, and fetal heart rate (HR). Subjects completed the state anxiety subscale of the State Trait Personality Inventory (STPI), then rested quietly in a semirecumbent position for a 5-min baseline period, followed by either a 5-min arithmetic or Stroop color-word task. Over the entire 5-min stress period and when averaged across all subjects, the stressors led to significant increases in maternal systolic BP and respiratory rate but changes in maternal HR, diastolic BP, and fetal HR were not significant. However, when subjects were dichotomized into groups that had above or below average anxiety scores [ANX(+) and ANX(-)], both groups had similar respiration rate increases to the stressors, but the BP and fetal heart rate (FHR) responses were significantly different. Women in the ANX(-) group had significantly greater BP responses compared to women in the ANX(+) group whereas the fetuses of ANX(+) women showed significant HR increases and the fetuses of ANX(-) women exhibited nonsignificant decreases. These findings suggest that women's acute emotional reactivity during pregnancy can influence fetal HR patterns and that a stress-induced increase in maternal BP is not the primary signal by which a women's stress response is transduced to her fetus. The results are consistent with the hypothesis that maternal psychological variables may shape the neurobehavioral development of the fetus.     

Family History of Hypertension and Cardiovascular Responses to Orthostatic Stress

Cardiovascular effects of orthostatic stress (sitting to standing) were assessed in 60 healthy young male subjects according lo family history of hypertension (half with a positive and half with a negative family history' of hypertension). Systolic (SBP) and diastolic blood pressure (DBF) were recorded on each successive heart heal using a non-invasive blood pressure tracking system. Heart rate (HR) and respiration rate (RR) were also recorded. During the postural change, characteristic phasic changes were shown with an initial fall and subsequent recover of SBP and DBF and a mirror image response in MR and RR. Phasic analysis of the pre-standing sit, peak/trough, and recovery stand values indicated group differences in the initial as well as the later phases of orthostatic response. In the initial phase, subjects with a positive family history of hypertension showed an earlier trough in systolic and pulse pressure and an earlier peak in heart rate response immediately on standing up. The level of the pulse pressure trough was also higher in these subjects. In the later standing phase, these subjects showed higher levels of pulse pressure. The results were interpreted in terms of increased sympathetic nervous system activity during the initial phase and structural and neurocirculatory abnormalities in the later phase of orthostatic regulation in individuals with a positive family history of hypertension.     

HEART RATE RESPONSE TO SOUND AND LIGHT

The heart rate (HR) response to five intensities of sound was examined in 18 subjects and to five intensities of light in 12 subjects. Each subject was tested on four occasions at monthly intervals. After covariance adjustment, significant acceleration to sound was found within the first 5 beats after stimulus onset but no significant deceleration occurred. There were no differences between testings. Individuals’ HR acceleration was reliable over testings and differing experimental contexts. No habituation occurred and no consistent relationship between HR response and ego strength was found. There was no significant HR response to light stimulation. The results were discussed in relation to Graham and Clifton's (1966) hypotheses concerning the relationship of the HR response to the orienting reflex (OR).     

Effects of coffee on cardiovascular responses to stress: a 14-week controlled trial.

We studied the cardiovascular responses to orthostatic and mental stress of 43 healthy subjects who daily received six cups of boiled or filtered coffee and of 21 healthy subjects who abstained from caffeine-containing beverages. All 64 subjects first received six cups of filtered coffee/day for 2 weeks. Then blood pressure (BP) and heart rate (HR) were recorded before, during, and after a "stand upright" test and a mental arithmetic test. Subjects were then randomized to either complete abstinence from caffeine-containing beverages (n = 21), or consumption of six cups of filtered coffee (n = 21), or consumption of six cups of boiled coffee/day (n = 22). The stress tests were repeated after subjects had been on these regimens for 8 weeks. Abstinence from coffee did not affect the responses of BP or HR to orthostatic stress, or the response of BP to mental stress. The increase in HR caused by mental stress was five beats/min less (p = 0.02) in the no-coffee group than in the filtered- (95% confidence interval -8.8 to -1.2) or boiled- (95% confidence interval -8.4 to -0.8) coffee group. It is concluded that elimination of caffeine decreases the HR response to mental stress.     

Electrodermal and phasic heart rate responses in the Guilty Actions Test: Comparing guilty examinees to informed and uninformed innocents

The present mock-crime study concentrated on the validity of the Guilty Actions Test (GAT) and the role of the orienting response (OR) for differential autonomic responding. N=105 female subjects were assigned to one of three groups: a guilty group, members of which committed a mock-theft; an innocent-aware group, members of which witnessed the theft; and an innocent-unaware group. A GAT consisting of ten question sets was administered while measuring electrodermal and heart rate (HR) responses. For informed participants (guilty and innocent-aware), relevant items were accompanied by larger skin conductance responses and heart rate decelerations whereas irrelevant items elicited HR accelerations. Uninformed participants showed a non-systematic response pattern. The differential electrodermal responses of informed participants declined across the test. With respect to the HR data, however, no habituation was observed. Findings suggest that GAT results could not exclusively be interpreted by referring to the OR.     

Bilateral carotid body resection in man enhances hypoxic tachycardia

In three groups of subjects we studied heart rate (HR) and ventilatory responses to progressive eucapnic hypoxia, steady-state hypercapnia with and without hypoxia, and hyperoxic and hypoxic breathholding (BH). Groups were six subjects about 25 years after bilateral carotid body resection (BR), eight subjects of an equally long period after unilateral resection (UR), and three control subjects similar to the study groups in age and pulmonary function (C). During progressive hypoxia, HR increased more in BR than in UR and C subjects. Ventilatory response was lowest in BR subjects (as expected). Steady-state hypoxic hypercapnia (end-tidal PO2, 60 Torr) depressed HR significantly more in C than in BR and UR subjects. Again, ventilatory response was lower in BR than in C subjects. HR progressively increased during BH initiated in hyperoxia (end-tidal PO2, 200 Torr) and hypoxia (end-tidal PO2, 70 Torr). In the BR group, the HR increment during hypoxia was significantly larger than that during hyperoxia. No such difference was apparent in UR and C groups. Thus, hypoxia with or without hypercapnia tends to accelerate HR in BR subjects whereas either less tachycardia or slowing is seen in UR and C subjects.     

Skin color and autonomic nervous system measures

A study has been performed in 50 subjects, 25 white and 25 black, measuring skin color (PI), basal skin resistance (SR) and amplitude of the galvanic skin response (GSR), and resting heart rate (HR) and the heart rate response (HRR) induced by a startle tone. A multiple correlation matrix revealed a statistically significant relationship between PI and SR and also GSR; between HR and HRR, and between SR and GSR. Analysis of the group differences revealed that blacks had significantly lower (darker) PI values, higher SR, greater GSR, and a higher HR and HRR. It is unclear from this study whether race or the intensity of skin color influenced the measured physiological responses.     

Possible influence on heart rate on tinnitus

Assuming the possibility of the inner ear damage due to a hemodynamic imbalance essentially due to an abnormal vasomotor regulatory response, the possibility that heart rate (HR) has a correlation with the onset and/or the enhancement of tinnitus is hypothesized. In fact, recent studies have drawn the influence of other factors than blood pressure, in normotensive subjects, in taking part to the regulation of peripheral resistance, outlining the importance of both cardiac output (CO) - which is a function of heart rate (HR) and stroke volume (SV) and SV itself as a dynamic component to baroreflex control of muscle sympathetic nerve activity (MSNA). From this point of view, it could be possible that a condition of bradycardia can enhance tinnitus regardless of its cause, and conversely that a more elevated HR can be related to a relief of this symptom.     

Self-biofeedback control of heart rate during exercise.

To improve cardiac adjustment to exercise, we developed a new self-biofeedback heart rate (HR) controller. Using this device, we analyzed time courses of HR, running speed (RS), stride length (ST) and pitch of gait (PI) in response to various preset HR levels in 7 normal human subjects. When HR was preset at 80 bpm, HR increased rapidly in response to exercise and exceeded the preset level at 12. 1 s with overshoot. At the preset HRs of 100, 120, 140 and 160 bpm, the HRs increased to each preset level at 39.2, 64.5, 58.5 and 83.0 s after the onset of exercise, respectively, and the HRs were adjusted with a range of +/- 4%. For all preset HRs, RS, ST and PI increased more rapidly than the HR and reached the maximum values within 30 s. During exercise, RS, ST and PI remained constant within 1.5-5.5 min. HR, RS, ST and PI increased in proportion to the preset HR. The increases in PI against HR (DeltaPI/DeltaHR) decreased with the higher HR level, and at HRs of 160-170 bpm, HR and PI showed identical rhythm. The increases in RS were produced by 18-59% increases in PI and by 12-44% increases in ST. We concluded that, using our newly developed self-biofeedback HR control system, we could control HR to a given preset value by a change in RS due to PI and ST.     

Ventilatory and heart rate responses at the onset of chair rotation in man

In the present study, we attempted to confirm whether pulmonary ventilation and heart rate increased immediately after passive chair rotation in man. Inspiratory minute volume (V(I)), tidal volume (V(T)), respiratory frequency (f), and heart rate (HR) were determined by breath-by-breath and beat-by-beat techniques before, during, and after rotation for a total of 45 s. It was found that V(I) significantly increased immediately after chair rotation, but HR remained almost constant. These results suggest that the activation of horizontal semicircular canals is one causal factor of ventilatory response at the onset of exercise with rotational movement in healthy subjects, but heart rate response is not.     

Effects of subject recruitment procedure on heart rate and skin conductance measures

This research was designed to determine whether the method employed to recruit subjects influences subsequent autonomic behavior. Skin conductance (SC) and heart rate (HR) measures were recorded from 60 female subjects equally divided among four groups which differed only with respect to the manner in which the subjects were recruited. The four groups employed included a volunteer group, a pay group, a subject-pool group, and a coerced group. Response comparisons were made between groups during a 10 min adaptation period followed by 20,5 sec bursts of 75 db white noise. Tonic levels and specific response magnitudes were scored for both SC and HR responses and, in addition, spontaneous SC activity was evaluated. Differences between the groups were observed in terms of HR and SC basal levels, and SC response magnitudes. The results supported the conclusion that autonomie behavior during a recording session is strongly influenced by subject recruitment procedure.     

The Role of Feedback in Control of Heart Rate Variability

The effects of contingent feedback (CF), non-contingent feedback (NCF). and no feedback (NF) on heart rate (HR) variability control were studied. Nine matched trios of subjects were given (ruining in HR variability control on 3 consecutive days. CF and NCF subjects attempted HR, variability control while HR feedback was continuously presented, and NF subjects attempted HR variability control without feedback. During the training periods the CF group produced reliably-lower mean HR variance than the NF group, but the NCF group was not reliably different from either of those groups. There was no significant difference among groups in negative linear trend across training periods, and the CF group did not continue to produce decreasing HR variances over sessions. However, the CF and NCF groups showed reliable quadratic trends, indicating an initial drop in HR variance followed by a return to pretraining levels. Both CF and NCF groups showed rapid, reliable increases in respiration rate during training periods. The results pose serious problems for studies which have reported feedback-related control of HR variability.     

Effects of Instructions and Contingency of Reinforcement on the Operant Conditioning of Human Phasic Heart Rate Change

The aim of these studies was to determine the effects of instructions and reinforcement contingency on phasic heart rate (HR) change. In Exp. I, 36 human subjects were given 20 conditioning trials with a muscletensing task which produced a phasic HR acceleration. The experimental manipulation produced an elevated baseline and allowed for the observation of instructed HR change during exercise. A 2 × 2 between subject design varied instructions (to increase or decrease the phasic tension-induced HR acceleration) and contingency (whether the verbal reinforcement was contingent on or unrelated to HR change) as factors. There was a significant instructional effect at the end of conditioning, with increase subjects producing more HR acceleration and decrease subjects less acceleration relative to pretrials. The instructional effect developed over trials and decrease subjects significantly improved with practice. There was no difference between contingent and non-contingent groups in either of the two conditions in ability to change HR in the instructed direction. This study shows the usefulness of the elevated baseline technique for cardiac research. A second experiment demonstrated that, in subjects not instructed to attempt HR change, the phasic HR response did not change in magnitude over conditioning. The results of these studies indicate that subjects are able to control phasic HR during physical-stress induced tension but biofeedback is not relevant for the production of such HR changes.     

AN EVALUATION OF FOREARM BLOOD FLOW AS A PSYCHOPHYSIOLOGICAL MEASURE

The usefulness of forearm blood flow (FBF) as a psychophysiological measure was investigated by comparing changes occurring during mental tasks in cardiovascular, sudomotor, and electromyographic measures. The measures were divided into those clearly physiologically independent and those physiologically related. ANOVA results showed that FBF, heart rate (HR), and skin conductance fluctuations (SCF) were equally reactive, and correlational analysis suggested that a close relationship existed between FBF, HR, and SCF, although correlations fell to near zero levels when intra-individual correlations were calculated with between task variance extracted. For some experimental purposes HR response may be considered equivalent to FBF response. The relationship between EMG and FBF was more variable, and tends not to support the idea that FBF is an indirect measure of muscle activity. The reliability of FBF in normal subjects at rest was poor, although it improved when measured during a simple task, and is probably stable enough for most experimental purposes.