Heart rate during conditioning in humans: Effects of UCS intensity, vagal blockade, and adrenergic block of vasomotor activity

Anticipatory cardiac deceleration estimates cognitive performance in virtual reality beyond tonic heart period and heart period variability

Anticipatory cardiac deceleration is the lengthening of heart period before an expected event. It appears to reflect preparation that supports rapid action. The current study sought to bolster anticipatory deceleration as a practical and unique estimator of performance efficiency. To this end, we examined relationships between deceleration and virtual reality performance under low and high time pressure. Importantly, we investigated whether deceleration separately estimates performance beyond basal heart period and basal high-frequency heart rate variability (other vagally influenced metrics related to cognition). Thirty participants completed an immersive virtual reality (VR) cognitive performance task across six longitudinal sessions. Anticipatory deceleration and basal heart period/heart period variability were quantified from electrocardiography collected during pre-task anticipatory countdowns and baseline periods, respectively. At the between-person level, we found that greater anticipatory declaration was related to superior accuracy and faster response times (RT). The relation between deceleration and accuracy was stronger under high relative to low time pressure, when good performance requires greater efficiency. Findings for heart period and heart period variability largely converge with the prior literature, but importantly, were statistically separate from deceleration effects on performance. Lastly, deceleration effects were detected using anticipatory periods that are more practical (shorter and more intermittent) than those typically employed. Taken together, findings suggest that anticipatory deceleration is a unique and practical correlate of cognitive-motor efficiency apart from heart period and heart period variability in virtual reality.

Characterizing cardiac autonomic dynamics of fear learning in humans

Understanding transient dynamics of the autonomic nervous system during fear learning remains a critical step to translate basic research into treatment of fear-related disorders. In humans, it has been demonstrated that fear learning typically elicits transient heart rate deceleration. However, classical analyses of heart rate variability (HRV) fail to disentangle the contribution of parasympathetic and sympathetic systems, and crucially, they are not able to capture phasic changes during fear learning. Here, to gain deeper insight into the physiological underpinnings of fear learning, a novel frequency-domain analysis of heart rate was performed using a short-time Fourier transform, and instantaneous spectral estimates extracted from a point-process modeling algorithm. We tested whether spectral transient components of HRV, used as a noninvasive probe of sympathetic and parasympathetic mechanisms, can dissociate between fear conditioned and neutral stimuli. We found that learned fear elicited a transient heart rate deceleration in anticipation of noxious stimuli. Crucially, results revealed a significant increase in spectral power in the high frequency band when facing the conditioned stimulus, indicating increased parasympathetic (vagal) activity, which distinguished conditioned and neutral stimuli during fear learning. Our findings provide a proximal measure of the involvement of cardiac vagal dynamics into the psychophysiology of fear learning and extinction, thus offering new insights for the characterization of fear in mental health and illness.

Browne J, Austin J, M. Myers M, Welch MG. The Welch Emotional Connection Screen: validation of a brief mother-infant relational health screen

AIM

The Welch Emotional Connection Screen (WECS), assesses mother-infant Emotional Connection in clinical settings. It includes: Attraction, Vocal Communication, Facial Communication, Sensitivity/Reciprocity and clinical decision of Emotional Connection (yes/no). We tested concurrent and construct validity of the WECS and associations with behavioural and physiological measures in preterm infants.

METHODS

Videos from 76 mothers-infants (gestational age 36 weeks) during an in-NICU caregiving paradigm were coded for maternal caregiving behaviour. Videos of mothers-infants were also obtained at 4 months during 10 minutes of face-to-face play (coded with WECS and for maternal positivity and infant social engagement) and the still-face paradigm (coded for infant behavioural approach towards mother; infant electrocardiogram acquired in vivo).

RESULTS

WECS maternal scores were positively associated with maternal sensitivity and quality of vocal contact at 36 weeks (caregiving) and maternal positivity at 4 months (face-to-face). WECS infant scores positively correlated with infant social engagement and maternal positivity during face-to-face interactions at 4 months. Infants from emotionally not connected dyads (vs. emotionally connected dyads) displayed autonomic dysregulation and less approach-seeking behaviour towards mother during interactive/play sessions of the still-face paradigm.

CONCLUSION

This preliminary evidence supports the WECS as a valid screen for rating mother-preterm infant emotional connection associated with healthier infant biobehavioural stress responding.

Visuocortical changes during a freezing-like state in humans

An adaptive response to threat requires optimized detection of critical sensory cues. This optimization is thought to be aided by freezing - an evolutionarily preserved defensive state of immobility characterized by parasympathetically mediated fear bradycardia and regulated by the amygdala-periaqueductal grey (PAG) circuit. Behavioral observations in humans and animals have suggested that freezing is also a state of enhanced visual sensitivity, particularly for coarse visual information, but the underlying neural mechanisms remain unclear. We induced a freezing-like state in healthy volunteers using threat of electrical shock and measured threat-related changes in both stimulus-independent (baseline) and stimulus-evoked visuocortical activity to low-vs. high-spatial frequency gratings, using functional MRI. As measuring immobility is not feasible in MRI environments, we used fear bradycardia and amygdala-PAG coupling in inferring a freezing-like state. An independent functional localizer and retinotopic mapping were used to assess the retinotopic specificity of visuocortical modulations. We found a threat-induced increase in baseline (stimulus-independent) visuocortical activity that was retinotopically nonspecific, which was accompanied by increased connectivity with the amygdala. A positive correlation between visuocortical activity and fear bradycardia (while controlling for sympathetic activation), and a concomitant increase in amygdala-PAG connectivity, confirmed the specificity of these findings for the parasympathetically dominated freezing-like state. Visuocortical responses to gratings were retinotopically specific, but did not differ between threat and safe conditions across participants. However, individuals who exhibited better discrimination of low-spatial frequency stimuli showed reduced stimulus-evoked V1 responses under threat. Our findings suggest that a defensive state of freezing involves an integration of preparatory defensive and perceptual changes which may be regulated by a common mechanism involving the amygdala.

The conditioning model of neurosis

The long-term persistence of neurotic symptoms, such as anxiety, poses difficult problems for any psychological theory. An attempt is made to revive the Watson-Mowrer conditioning theory and to avoid the many criticisms directed against it in the past. It is suggested that recent research has produced changes in learning theory that can be used to render this possible. In the first place, the doctrine of equipotentiality has been shown to be wrong, and some such concept as Seligman's “preparedness” is required, that is the notion that certain CS are biologically prepared to be more readily connected with anxiety responses than others. In the second place, the law of extinction has to be amended, and the law of incubation or enhancement added, according to which the exposure of the CS-only may, under certain specified conditions, have the effect of increasing the strength of the CR, rather than reducing it. The major conditions favouring incubation are (1) Pavlovian B conditioning, that is a type of conditioning in which the CR is a drive; (2) a strong UCS, and (3) short exposure of the CS-only.

Effects of extinction on classical conditioning and conditioning-specific reflex modification of rabbit heart rate

Understanding the mechanisms of fear extinction has become increasingly important for treating a number of disorders, particularly post-traumatic stress disorder. Conditioning of rabbit heart rate (HR) is an established model for studying fear, yet little is known about procedures for extinguishing it other than repeated presentations of cue(s) associated with the fear-inducing event. The following study examined the effects of conditioned stimulus (CS) alone, unconditioned stimulus (US) alone, unpaired CS/US presentations, continued CS-US pairings, or no further stimulation on rabbit HR following HR conditioning. We have previously shown the rabbit HR response to the US can change as a function of learning when measured in the absence of the CS, a phenomenon referred to as conditioning-specific reflex modification (CRM). More specifically, the HR exhibits a deceleration in response to the US reminiscent of the conditioned bradycardia that develops to the CS. Consequently, the following study also examined the effects of extinction treatments on HR CRM. For HR conditioned responses (CRs), CS-alone and unpaired CS/US presentations were the most successful extinction treatments. For HR CRM, all conditions led to a reduction in CRM except for a subset of rabbits that maintained high levels following unpaired extinction, indicating a dissociation between extinction of HR CRs and CRM. The findings highlight the parameters of HR extinction, the transient nature of HR CRM, vagal involvement in both acquisition and extinction of HR CRM, and suggest that HR CRM cannot be fully explained as a CR that has generalized from the CS to the US.

Fear-conditioned respiration and its association to cardiac reactivity

This study aimed to investigate ventilatory correlates of conditioned fear responses. Respiratory, end-tidal carbon dioxide pressure (PetCO(2)) and heart rate changes were studied in a differential fear-conditioning paradigm. Forty-two participants viewed pictures of faces. One picture (CS+) was followed by a human scream (US) during the acquisition phase, but not in a subsequent extinction phase. Conditioning of PetCO(2) (decrease), respiratory cycle time (decrease) and inspiratory duty time (increase) was established and subsequently extinguished. When participants were clustered according to their conditioned PetCO(2) responses during acquisition, only a group showing a conditioned decrease in PetCO(2) showed also a differential cardiac acceleration, a decrease in expiratory duration and an increase in inspiratory duty time in response to the CS+. These results suggest that preparation for defensive action is characterized by a tendency towards hyperventilation and cardiac acceleration.

Conditioning-specific reflex modification of rabbit (Oryctolagus cuniculus) heart rate

Conditioning-specific reflex modification (CRM) describes changes in rabbit (Oryctolagus cuniculus) nictitating membrane responses (NMR) to an unconditioned stimulus (US) when the US is tested by itself after pairings of tone and electrodermal stimulation. Although CRM has been replicated, it is unclear whether it occurs in response systems other than that of the NMR. The authors report that CRM of rabbit heart rate (HR) can occur following HR conditioning. A US that elicits HR acceleration before conditioning can elicit HR deceleration after conditioning. The rabbits' electrocardiograms showed both HR conditioning and HR CRM were correlated with an increased PQ interval--an index of parasympathetic function mediated by the vagus. The data suggest conditioned HR deceleration can generalize from conditioned stimulus to US as a function of conditioning.

Classical conditioned response of rectosigmoid motility and regional cerebral activity in humans

The relationship between the central processes of classical conditioning and conditioned responses of the gastrointestinal function is incompletely understood in humans. We tested the hypothesis that the rectosigmoid motility becomes conditioned with anticipatory painful somatosensory stimulus and that characteristic brain areas become activated during anticipation. In nine right-handed healthy male subjects, a loud buzzer (CS, conditional stimulus) was paired with painful transcutaneus electrical nerve stimulation to the right hand (unconditional stimulus). Rectosigmoid muscle tone measured by the barostat as the intrabag volume, phasic contractions of the bowel measured as the number of phasic volume events (PVEs), and regional cerebral blood flow assessed by positron emission tomography (PET), were measured before and after conditioning. Following conditional trials, the bag volume after CS alone did not show significant changes between before and after the stimulus, but the number of PVEs after 2-minute interval of the CS alone was significantly greater than that before the stimulus (P < 0.05). The PET data showed the conditioning elicited significant cerebral activation of the prefrontal, anterior cingulate, parietal and insula cortices (P < or = 0.001, uncorrected). Rectosigmoid motility can be conditioned with increase in phasic contractions in humans.

Stuttering, emotions, and heart rate during anticipatory anxiety: a critical review

Persons who stutter often report their stuttering is influenced by emotional reactions, yet the nature of such relation is still unclear. Psychophysiological studies of stuttering have failed to find any major association between stuttering and the activity of the sympathetic nervous system. A review of published studies of heart rate in relation to stressful speech situations indicate that adults who stutter tend to show a paradoxical reduction of heart rate compared with nonstuttering persons. Reduction of heart rate has also been observed in humans and mammals during anticipation of an unpleasant stimulus, and is proposed to be an indication of anticipatory anxiety resulting in a "freezing response" with parasympathetic inhibition of the heart rate. It is suggested that speech-related anticipatory anxiety in persons who stutter is likely to be a secondary, conditioned reaction based on previous experiences of stuttering.

EDUCATIONAL OBJECTIVES

The reader will be able to: (1) describe how the autonomic nervous system is modulated by emotional responses; (2) explain how anticipatory fear often results in inhibition of heart rate due to parasympathetic activation; (3) discuss why emotional reactions in persons who stutter may be secondary to negative experiences of speech problems.

Rapid cardiac adaptation to exercise demand signal and execution of maximal leg muscle contraction

We investigated the neural regulation of the cardiac interval to an exercise demand signal and to a repeated exercise in 20 healthy human subjects. Electrocardiogram (ECG), muscle torque, and electromyogram (EMG) were simultaneously measured and their time relationships compared before and during the exercise. The R-R interval of ECG was directly increased by the exercise demand signal itself before the onset of EMG but not reflexly by muscle contraction. The cardiac interval decreased at the onset of exercise. Under the condition of repeated maximum eccentric training, the resting cardiac interval decreased prior to the exercise, whereas the brief increase in cardiac interval to the exercise demand signal remained unchanged. These results suggested that when autonomic nerve activity to the pacemaker is activated by the exercise demand signal, an initial effect of vagal nerve activity appears, and an effect of vagal nerve withdrawal and/or sympathetic nerve activity then appears. The responses of the heart and leg skeletal muscle at the onset of exercise are not synchronized, and the cardiac interval is controlled by vagal and sympathetic nerve activities to effect a transition to a high heart rate as quickly and smoothly as possible.

Classical conditioning of the human blood pressure response

The object of this experiment was to demonstrate that blood pressure responses could be classically conditioned in human subjects and to describe the topography of the conditioned response. Despite clear evidence for classical blood pressure conditioning in animals there is little evidence concerning a clear demonstration of the phenomenon in human subjects, and no description of the form of the conditioned response. A 'neutral' 8-s 70-db tone (CS) was paired with a 500-ms electric shock (UCS) in a delay conditioning paradigm. Conditioned subjects were compared to a control group that received the CS and UCS on a truly random schedule. The subjects in the conditioning group showed a conditioned blood pressure response that emerged during the last 4 s of the 8-s CS. The results differ from those obtained from animals, where the CR typically emerges during the first half of the CS. These data may have implications for the role of learning in hypertensive disorders.

Covariation of Phasic Cardiovascular and Cortical Responses

Abstract Effects of maintaining an alert state on event-related brain potentials (ERPs) and evoked cardiovascular responses were examined in an auditory detection task. Subjects were instructed to detect a possible difference in frequency between two successively presented tones in 5 s periods. Two types of trials were compared. In the first no tones were presented and subjects had to maintain an alert state for the full five seconds (uninterrupted trials). In the second type the alert state was interrupted by the presentation of visual stimuli which were presented in the second half of the 5 s period (interrupted trials). Both types of trial elicited ERPs with a negative shift consisting of a frontal and a parietal part. Uninterrupted trials elicited a stronger and longer lasting negative shift. This difference was maximal at parietal sites. The stronger negative shift was accompanied by a stronger deceleration in the heart rate response, which started at about the same time as the cortical effect but lasted somewhat longer. Furthermore, uninterrupted trials evoked a stronger decrease in the blood pressure response. This effect showed the expected delay when compared to the effect on heart rate (HR). The cardiovascular data confirmed the hypotheses concerning effects of maintaining an alert state, but the cortical data partly contradicted them. Altogether, the current findings do not contradict an active network involved in alertness, but they do not confirm the expected stronger involvement of the right hemisphere and involvement of prefrontal areas in this function.

Sympathetic nervous activity and arterial pressure responses during rest and acute behavioral stress in SHR versus WKY rats

The object of this experiment is to compare changes in renal sympathetic nerve activity (SNA), mean arterial blood pressure (MAP) and heart rate (HR) during rest and behavioral stress in 12-14 week old spontaneously hypertensive rats (SHR; N = 12) and normotensive Wistar-Kyoto (WKY; N = 12) controls. Animals were behaviorally trained by following a 15 s auditory conditional stimulus (CS+) with a 1/2 s tail shock. Resting MAP was higher (p < 0.001) in SHR (154 +/- 3 mmHg, mean +/- SEM) compared to WKY (116 +/- 3 mmHg); conversely, there was no difference in the average resting HR. The pattern of the SNA and MAP changes during the CS+ was similar across groups, but the amplitude was larger in the SHR. The CS+ stress stimulus evoked an initial transient MAP increase averaging 14 +/- 2 mmHg in the SHR compared to 4 +/- 1 mmHg in the WKY. This pressor response was preceded by a sudden burst of SNA averaging 177 +/- 22% over baseline in SHR versus 105 +/- 13% for the WKY. HR decreased in SHR only during the second component of the CS+ trial despite the large increase in SNA. We conclude that (1) SHR have higher reactivity than WKY to stress in SNA and MAP; (2) both SHR and WKY have greater SNA and MAP responses to CS+ than CS-(i.e., the discriminative paradigm was effective); (3) control of sympathetic and parasympathetic nervous activity during sustained stress differs remarkably in hypertensive and normotensive subjects; and (4) SHR blood pressure effector mechanisms may have a higher responsiveness to sympathetic nervous activity as compared to WKY.

Dementia and response to pain in the elderly

To investigate the effect of dementia on response to pain, 51 community-dwelling, generally healthy, cognitively intact individuals > or = 65 years old and 44 community- or nursing home-dwelling persons > or = 65 years old with varying severity of dementia were studied. Cognitive status was assessed by standardized clinical evaluation and psychometric test performance. The following responses were measured before, during and after a standard venipuncture procedure: heart rate, the amplitude of respiratory sinus arrhythmia (RSA), self-reported anxiety and pain, and videotaped facial expressions. Although RSA did not differentiate procedural phases, in both samples, mean heart rate increased in the preparatory phase and decreased in the venipuncture phase. Independent of age, increasing severity of dementia was associated with blunting of physiologic response as measured by diminished heart rate increase in the preparatory phase and heart rate increase with venipuncture. Dementia significantly interfered with the subjects' ability to respond to direct questions about anxiety and pain. Those who were able to respond were relatively accurate self-assessors: higher anxiety was associated with greater magnitude heart rate responses. Facial expression was increased in demented individuals but it could not be classified by specific emotions. We conclude that dementia influences both the experience and reporting of pain in elderly individuals.

Illusions, arithmetic, and the bidirectional modulation of vagal control of the heart

Behavioral contexts can evoke a variety of autonomic modes of response, characterized by reciprocal, coactive, or independent changes in the autonomic divisions. The present study investigated the modes of autonomic response to visual illusion and mental arithmetic tasks, by the use of noninvasive measures of sympathetic (pre-ejection period; PEP) and parasympathetic (respiratory sinus arrhythmia; RSA) cardiac control. As previously demonstrated, mental arithmetic was associated with a reciprocal pattern of sympathetic activation and vagal withdrawal. The illusion task, however, yielded a distinct mode of vagal activation in the absence of sympathetic change. Responses within tasks were reliable. In contrast to the general intertask consistency reported for stress tasks that yield similar autonomic modes of response, however, neither PEP nor RSA responses were correlated across the illusion and arithmetic tasks. This may be attributable to the dissimilar modes of autonomic control evoked by these tasks. The distinct modes of autonomic response to arithmetic and illusions emphasize the importance of a bivariate model of autonomic control, and may offer important experimental tools for psychophysiological studies of autonomic control.

Autonomic cardiac control. III. Psychological stress and cardiac response in autonomic space as revealed by pharmacological blockades

Behavioral contexts can evoke a variety of autonomic modes of response, characterized by reciprocal, coactive, or independent changes in the autonomic divisions. In the present study, we investigated the reactive autonomic control of the heart in response to psychological stressors, using quantitative methods for analyzing single and double autonomic blockades, and through the use of noninvasive indices based on heart period variability and systolic time intervals. Analysis of the effects of pharmacological blockades revealed an overall pattern of increased sympathetic and decreased parasympathetic control of the heart during speech stress, mental arithmetic, and a reaction-time task. Unlike the classical reciprocal sympathetic-parasympathetic response to orthostatic challenge, however, the responses of the autonomic branches to stress were uncorrelated. This reflected notable individual differences in the mode of autonomic response to stress, which had considerable stability across stress tasks. The putative noninvasive indices of sympathetic (preejection period) and parasympathetic (respiratory sinus arrhythmia) control changed in accord with the results of pharmacological blockades. Together, these results emphasize the substantial individual differences in the mode of autonomic response to stress, the advantages of a quantitative approach to analyzing blockade data, and the importance of validity estimates of blockade data.

Ivanov-Smolensky conditioning: relationship between CR and UR form and intensity

The Ivanov-Smolensky conditioning procedure involves a CS followed by a command (US). There are two URs--an instructed UR and a reflexive UR such as an autonomic reaction. Anticipatory responses during the CS, of either the instructed or reflexive UR, provide a measure of conditioning. We examined whether the reflexive CR and UR are similar in form, and whether larger reflexive CRs and URs are associated with larger instructed URs. Subjects were asked to exhale "quickly and powerfully" (exhalation was thus the instructed UR) either following (Forward) or prior to (Backward) a light CS; a change in heart rate to the CS (reflexive CR) alone was the index of conditioning. The heart rate CR and UR were both deceleratory in nature, although the onset of the CR was faster than the UR. In addition, Backward-conditioned subjects demonstrated some degree of inhibitory control by the CS. Finally, the CR intensity was inversely related to exhalation magnitude.

Autonomic space and psychophysiological response

Contemporary findings reveal that autonomic control of dually innervated target organs cannot adequately be viewed as a continuum extending from parasympathetic to sympathetic dominance. Rather, a two-dimensional autonomic space, bounded by sympathetic and parasympathetic axes, is the minimal representation necessary to characterize the multiple modes of autonomic control. We have previously considered the theoretical implications of this view and have developed quantitative conceptual models of the formal properties of autonomic space and its translation into target organ effects. In the present paper, we further develop this perspective by an empirical instantiation of the quantitative autonomic space model for the control of cardiac chronotropy in the rat. We show that this model (a) provides a more comprehensive characterization of cardiac response than simple measures of end-organ state, (b) permits a parsing of the multiple transformations underlying psychophysiological responses, (c) illuminates and subsumes psychophysiological principles, such as the Law of Initial Values, (d) reveals an interpretive advantage of expressing cardiac chronotropy in heart period rather than heart rate, and (e) has fundamental implications for the direction and interpretation of a broad range of psychophysiological studies.

Conditioned nausea after cancer chemotherapy and autonomic nervous system conditionability

There are marked individual differences in conditioned nausea after cancer chemotherapy. To examine if part of this variation is associated with individual differences in autonomic nervous system conditionability, the present study addressed whether patients with conditioned nausea acquired conditioned heart rate and electrodermal responses at a different rate than patients without conditioned nausea. Of 28 relapse-free patients who had completed cisplatinum treatment for testicular cancer between 1981 and 1986, 10 reported persistent conditioned nausea, 8 extinguished conditioned nausea and 10 no conditioned nausea. These three groups were subjected to a differential conditioning paradigm with 8 sec pictorial stimuli (circles and triangles) serving as conditioned stimuli for an unconditioned electric shock while heart rate and electrodermal activity was monitored. There were 4 habituation, 8 acquisition and 8 extinction trials with each of the two cues. Analyses of variance using nausea status as the independent variable and physiological responses as the dependent lended some support to the notion that conditioned heart rate deceleration developed in response to the reinforced compared to the nonreinforced cue during acquisition in the two groups with persistent or extinguished conditioned nausea but not in the group with no conditioned nausea. In addition, patients that displayed good, as compared to poor heart rate conditionability during acquisition, were more likely to have persistent conditioned nausea, whereas those who showed poor heart rate conditioning mostly were those without conditioned nausea. Electrodermal variables revealed no systematic differences between groups. This tentatively supports that individual differences in parasympathetic but not sympathetic nervous system conditionability may be associated with individual differences in conditioned nausea resulting from cancer chemotherapy.

Multiple modes of operation of cardiac autonomic control: development of the ideas from Cannon and Brooks to the present

Since Cannon's time much emphasis has been placed on reciprocal control of the organ function by the autonomic nerves while other modes of control has been neglected. In our laboratory, prompted by Dr. Brooks, we initiated the study of the autonomic control of the heart by recording simultaneously the activity of cardiac sympathetic and parasympathetic nerves under a variety of conditions in chloralose anesthetized dogs. We have demonstrated that the central nervous system exercises reciprocal as well as non-reciprocal pattern of control over the two arms of the autonomic outflows under different physiological and behavioral conditions, and that each mode of control has an important functional significance.

Single-unit activity in the dorsomedial prefrontal cortex during the expression of discriminative bradycardia in rabbits

Much recent evidence suggests that the medial prefrontal cortex (PFCm) participates in the development and/or expression of learned, primary bradycardiac adjustments in rabbits. Accordingly, the present experiments were undertaken to determine whether single-unit activity in the precentral agranular and anterior cingulate regions of the PFCm is systematically affected by differential aversive Pavlovian conditioning and, if so, whether such activity is correlated with concomitant heart rate (HR) variables. In these studies, extracellular recordings were made during a training procedure that involved two distinctive, tone conditioned stimuli (CSs); one of these (CS+) was often paired with eye-shock (unconditioned stimulus, US), whereas the other (CS-) was never so paired. Of the 100 spontaneously-active cells whose activity was so evaluated, 74 were found to be tone-responsive and could be classified as belonging to one of 5 subpopulations on the basis of their specific patterns of evoked changes in discharge; additional data suggested that these cells were also generally responsive to the eye-shock US. Regarding the effects of training, the vast majority of cells in these subpopulations showed greater evoked activity changes on CS+, as opposed to CS-, trials, irrespective of the sign (i.e. increase and/or decrease) of their responses. This finding was not confounded by differences in baseline activity preceding CS+ vs CS- trials, which was generally characterized as being both irregular and unrelated to concomitant HR variables; nor could it be attributed to unconditioned responses biases. Thus, the discriminative activity patterns of these cells appeared to reflect the differential Pavlovian contingencies in effect. Moreover, approximately half of these cells exhibited tone-evoked activity changes that were reliably correlated with concomitant HR changes on a trial-by-trial basis. Consequently, the present data indicate that training-induced changes in the CS-evoked activity of PFCm cells are significantly related to aversively conditioned bradycardia in rabbits.

Autonomic activity

A review such as this can do no more than provide an indication of the issues involved in using autonomic activity as a means of providing a "window on the brain." Several points arise. One of the most important is that of careful and appropriate use of techniques available. One well-known textbook of experimental psychology published some time ago advocated the use of two dimes applied to the palm of the hand for the measurement of electrodermal activity. It was this sort of recommendation that led to the use of psychophysiological measurement falling into disrepute. As indicated in the second section, it is important to understand fully the peripheral mechanisms involved before measurement of electrodermal activity can be usefully carried out. Appropriate use of silver/silver chloride electrodes and physiologically appropriate levels of saline in the electrolyte medium can lead to accurate and repeatable measurement where artefact is not carelessly introduced. Equally important is the context in which studies are carried out. The psychological invasiveness of the technique is important to recognize, and it is here that measurement of autonomic activity probably scores over other methods that are available insofar as very little restriction of the subject is required and the number of transducers that must be applied is minimal. The measurement of autonomic activity within the totality of the experimental context is all important. As an example Dawson and Schell investigated the SCR to words which had previously been associated with shock. When these words were presented to the ear to which attention was not directed in a dichotic listening paradigm, an SCR could be elicited although the subject was unaware of the presentation of the stimulus. The importance of the Dawson and Schell study was the care that they took to make sure that the subject really was unaware of the critical stimulus and had not momentarily switched attention from the attended ear. More important, their experiment, in contrast to some which had gone before, used a balanced design in which the critical stimuli were presented on different occasions to each ear. As a result of this it was found that critical stimuli, which were presented to the left ear, right hemisphere, gave rise to SCRs, even when the subject was not aware of their presentation, whereas stimuli presented to the right ear, left hemisphere elicited no response.(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiopulmonary adjustments during operant heart rate control

Twenty-three healthy men and women participated in a 5-session experiment in which they attempted to increase and decrease their heart rate with the assistance of visual analogue biofeedback. As a group subjects did successfully raise and lower heart rate from resting baseline. These changes in heart rate were closely paralleled by changes in V, a measure of cardiac vagal tone. Heart rate slowing was associated with increases in V, and heart rate speeding was associated with decreases in V. Respiration rate and amplitude did not differ significantly between heart rate slowing and speeding trials, and covariance analysis indicated that respiratory changes did not account for the heart rate or V effects. The weighted coherence between respiration and heart rate showed that cardiopulmonary coupling increased during heart rate slowing and decreased during heart rate speeding. Individual differences in cardiac vagal tone and cardiopulmonary coupling were unrelated to heart rate speeding and slowing performance.

Conspecific screams and laughter: cardiac and behavioral reactions of infant chimpanzees

The present study examined cardiac and behavioral reactions of infant chimpanzees to white noise and to conspecific screams and laughter. Chimpanzee screams evoked typical deceleratory cardiac orienting responses. Analysis of stimulus-evoked changes in respiratory sinus arrhythmia suggested that this cardiac deceleration arose from an increase in parasympathetic activity. In contrast, chimpanzee laughter evoked notable cardiac acceleration. Laughter also evoked vocalizations from the infant subjects, which were reminiscent of adult threat-barks. Analysis of respiratory sinus arrhythmia suggested that the cardioacceleratory response likely resulted from sympathetic activation, and was not associated with an inhibition of parasympathetic activity. The autonomic and vocal responses to laughter emerged early in development, were minimally dependent on social contact with adults, and declined in magnitude with increasing age. A consideration of the phylogeny of laughter raised the possibility that the functional reaction to this vocalization may be related to its origin in more primitive agonistic facio-vocal signals.

Does heart rate differentiate neurotic from normal people in a conditional reflex test?

This study is to compare heart reactivity between normals and anxiety neurotic patients. Five male and five female patients with anxiety neurosis and four male and five female normal persons were submitted to classic delayed conditional reflexes with different probabilities of reinforcement (shock), to a defensive instrumental conditional reflex, and to a neutral nonreinforced stimulus. The basal heart frequency was higher in neurotics and in women than in normals and men. The conditional stimulus (CS) associated with a shock generally produced a bradycardia in normal individuals and in neurotic men, but a tachycardia in neurotic women (effects most pronounced in cases with 100% shock probability). The instrumental CS caused a tachycardia in all of the groups, with highest values in neurotic women. The neutral stimulus produced bradycardia in all persons. The aftereffect of the light stimulus depended on whether a shock was administered and on the CS. The differences between neurotics and normals are explained as caused by the heightened excitatory level of the CNS of the neurotic group, produced by the unspecific activating effect of chronic anxiety, and differences of plastic processes in both groups, resulting in different effects of phasic anxiety on the heart. Complex inhibitory-excitatory interactions of the sympathetic and the vagal system underlying the heart rate changes may be assumed. Possible mechanisms leading to sex differences are discussed.