One-trial cardiac conditioning in dogs

Our interest in cardiovascular conditioning, particularly the fact that conditional tachycardia has been observed in many dogs after only one or two combinations of conditional and unconditional stimuli, led us to investigate conditioning using a single application of an unconditional stimulus. Initially we studied the effect of orienting stimuli (soft tones) on the heart rate in 9 dogs. After 30–100 presentations of the tones alone, each dog received on one occasion a 25-volt shock (sufficient to cause yelping and struggling) to a leg as unconditional stimulus immediately following a tone. Thereafter 30–100 additional tones were presented with no further shock. Little or no heart rate change occurred during the orienting tones (before shock). Three types of cardiac changes occurred during experimental sessions after the shock: 1) Increased heart rate during the tones in 5 dogs; 2) Generalized lowering of heart rate during all experimental sessions after shock in 4 dogs; 3) Electrocardiographic changes during tones in 3 of the dogs also showing the generalized decrease in heart rate. No motor flexion conditional reflexes developed. Tones an octave different in pitch from the one associated with the shock also caused approximately the same heart rate changes, indicating lack of differentiation. This one-trial cardiac conditioning persisted after the single conditioning trial for more than a month in 2 dogs and for at least 3 to 5 sessions in the other dogs.     

The effect of unilateral stellectomy on the regulation of heart rate during behavioral stress.

Changes in heart rate were examined during classical aversive conditioning before and after either left (n = 10) or right stellectomy (n = 8). Heart rate (HR) significantly (p less than 0.01) increased in response to the conditional stimulus with a further increase noted during the unconditional stimulus. After right stellectomy (RSGx) the aversive stress elicited a significantly (p less than 0.01) smaller increase in heart rate (peak HR change: control 66.8 +/- 6.0; RSGx 36.1 +/- 6.8 beats/min). In contrast left stellectomy did not significantly alter the heart rate conditional response. Cardioselective beta-adrenergic receptor blockade, metoprolol HC1 (BB, 1.0 mg/kg, n = 8), significantly (p less than 0.01) reduced the heart-rate conditional response (peak HR change: control 66.8 +/- 6; BB 25.1 +/- 3.8 beats/min) to the same extent as noted during RSGx. These data suggest that the heart-rate increases elicited by aversive stress are mediated in part by sympathetic nerves that originate or pass through the right stellate ganglion. The residual HR increase noted after RSGx or BB probably results from the withdrawal of cardiac parasympathetic activity.     

The effect of unilateral stellectomy on the regulation of heart rate during behavioral stress

Changes in heart rate were examined during classical aversive conditioning before and after either left (n=10) or right stellectomy (n=8). Heart rate (HR) significantly (p<0.01) increased in response to the conditional stimulus with a further increase noted during the unconditional stimulus. After right stellectomy (RSGx) the aversive stress elicited a significantly (p<0.01) smaller increase in heart rate (peak HR change: control 66.8 +/- 6.0; RSGx 36.1 +/- 6.8 beats/min). In contrast left stellectomy did not significantly alter the heart rate conditional response. Cardioselective beta-adrenergic receptor blockade, metoprolol HCl (BB, 1.0 mg/kg, n=8), significantly (p<0.01) reduced the heart-rate conditional response (peak HR change: control 66.8 +/- 6; BB 25.1 +/- 3.8 beats/min) to the same extent as noted during RSGx. These data suggest that the heart-rate increases elicited by aversive stress are mediated in part by sympathetic nerves that originate or pass through the right stellate ganglion. The residual HR increase noted after RSGx or BB probably results from the withdrawal of cardiac parasympathetic activity.     

Conditioning the cardiorespiratory dynamics of locomotion in dogs

In 17 dogs blood pressure in the carotid artery, heart rate, pneumogram and actogram of the hind leg were recorded during rest and during locomotion on a treadmill. The increases in cardiorespiratory dynamics which occurred during locomotion were then conditioned. The conditional stimulus was represented by the noise and vibration of the treadmill. It was determined that conditional changes in cardiorespiratory dynamics can be formed quickly on the basis of locomotion. Qualitatively the changes were the same as the unconditional changes, and their magnitude was 60 to 70 per cent that of the unconditional changes. Conditional increase in cardiorespiratory dynamics was most intensive in the first 30 seconds from the onset of the conditional stimulus. In acute extinction of these conditional changes, movements of the extremities were inhibited first, followed by inhibition of increased blood pressure, then inhibition of increased heart rate, and last, inhibition of increased respiratory rate. In another series of experiments on five dogs cardiorespiratory responses were conditioned to a sudden change from moderate locomotion (50 m per min) to rapid locomotion (200 m per min). Increased cardiorespiratory dynamics could be conditioned easily. Increased circulation of blood and increased respiratory rate on exposure to conditional stimuli signalling muscular exertion can be considered an important preparation of the organism for actual muscular activity. This preparation also takes place in natural life conditions.     

Respiratory conditional reflex formation with CO2 and electric shock as unconditional stimuli

In 12 birds used in a CO₂ conditioning experiment there was no evidence of the formation of either a respiratory or a cardiac conditional reflex. Tone and light separately or together were used as conditional stimuli. CS-US intervals ranging from 0.5 to 10 seconds were used. CO₂ concentrations up to 7.4% were also employed. In the shock conditioning experiments six of seven birds showed a respiratory change to the conditional stimulus. In one pigeon perfect differentiation was obtained between the reinforced and nonreinforced tones. The marked difference in conditionability of sensory and chemical stimuli to the “respiratory center” is discussed in relation to the central nervous system connections of the respiratory control mechanism.     

Blood flow,blood pressure and heart rate changes accompanying hind leg flexion in conditional and unconditional reflexes

Results

During flexion of the hind leg to US or CS, as well as during spontaneous lifting of the leg, the blood flow in the appropriate femoral artery suddenly increases for 10–14 seconds, systemic blood pressure shows transient decrease, while heart rate and respiratory movements are accelerated. To perform one flexion and subsequent extension about 7 ml extra blood flow is necessary during UR and 5 ml during CR. During acute extinction of the CR the described vegetative changes become less and less, parallel with the gradual decrease of flexor movement of the hind leg. The sequence of extinction of the individual measured parameters was as follows: flexion, blood pressure, blood flow, heart rate, and lastly, respiration. In the mechanism of the vegetative changes accompanying the conditional hind leg flexion three main components are involved: (1) muscular-visceral reflexes originating from different receptors of the contracting muscles, (2) the emotional changes, and (3) the conditional component as a separate conditional reflex for each measured parameter. Principles underlying the formation of conditional reflexes are discussed under the headings ofschizokinesis, peripheral andcentral stimulations.Organ responsibility is the basis for the formation of the conditional reflex.     

Effect of dopamine on diuresis and its role in forming a renal CR

Four female mongrel dogs were used. Three had both ureters transplanted to the surface of the abdomen and one had a unilateral nephrectomy on the left and the right ureter transplanted to the abdomen. In dogs with externalized ureters our results with dopamine show changes in cardiac rate and renal secretion. The method used was 1) injection of dopamine, 2) measurement of subsequent changes in renal secretions (unconditional reflex), 3) and heart rate (HR). After 40 daily injections im of 2.5 mg/kg in normal saline the possible production of a diuretic CR was tested by injecting normal saline im and a tone was used as a signal. The control for normal saline showed no change in HR nor any of the constituents measured. The dopamine injection resulted in an increase of epinephrine in the urine of 300–600 per cent for 45 minutes; of norepinephrine of 200–500 per cent for 45 minutes; of an increase of 50 per cent in urine volume for 45 or more minutes; of absolute Na secretion of 49 per cent, of K, 20 per cent; of creatinine, 39 per cent (average in 3 dogs for 45 minutes diuresis). When the conditional stimulus (normal saline and tone) was given after several months training with the conditional signal and the injection of dopamine, there was no significant CR change to the HR nor any of the above components of urine. The conclusion is that in spite of the great increase of urine volume and composition of above substances there was no significant increase to the signals for the im injection of dopamine,i.e., no conditioning to dopamine.     

Failure to develop a conditional reflex by stimulation of the cephalad portion of the severed vagosympathetic trunk: Its significance in terms of the central connections of the vagus

Stimulation of the central stump of either vagosympathetic trunk in the dog, the contralateral nerve remaining intact, regularly provoked deep respiratory movements with forceful expiration, followed by a period of apnea, and a fall in blood pressure, systolic and diastolic, of 20–60 mm/Hg. Stimulation of the cephalad portion of the left nerve provoked brief acceleration of heart rate during the period of hyperventilation, followed by bradycardia; when the stimulus was applied to the central stump of the right nerve heart rate remained relatively unchanged. When a 12-second tone as a conditional stimulus (CS) was reinforced during its last six seconds with such stimulation of the vagosympathetic trunk as an unconditional stimulus (US), despite the striking visceromotor responses elicited by the US, no conditional reflex was established even after more than 3,400 trials in 16 dogs (34–781 trials per animal).     

Psychophysiological mechanisms involved in the affective regulation and food restriction of women at risk of suffering from bulimia nervosa

The aim of the study was to explore the effect of visualizing food images under different mood states and food restriction conditions on the emotional modulation of two defense reflexes (startle reflex and cardiac defense). 72 women at risk of suffering from bulimia nervosa were assigned to two groups: 1) a group under induced positive, neutral, or negative mood state and, 2) a 6-hour-food-deprived group or a non-deprived group. Second-by-second heart rate and electromyogram activity from the orbiculari oculi region were recorded after the auditory stimulus. The results showed that, while viewing food images, non-deprived women under negative mood state potentiated the cardiac defense response and the startle motor reflex. Results are discussed in the context of emotional eating theories and Peter Lang's motivational priming model.     

Transference,discrimination and reversal

A total of 68 subjects-17 normal volunteers, 17 hospitalized paranoid schizophrenics, 17 non-paranoid schizophrenics, and 17 patients with organic brain syndrome-were compared on their performance on the different phases of a specially devised conditioning procedure. This procedure is composed of (1) acquistion of the conditional reflex,i.e., squeezing a rubber bulb to the presentation of white light; (2) transference from a visual conditional stimulus to a verbal conditional stimulus and back to the visual conditional stimulus; (3) conditional stimulus differentiation; and (4) conditional stimulus reversal. Performance profiles of the normal and of the pathological groups were established and the statistically significant differences among the sub-groups of the experimental population were described. The clinical significance of these findings is discussed.     

Form and characteristics of the cardiovascular conditional response in Rhesus monkeys

Three Rhesus monkeys restrained in primate chairs were exposed to several Pavlovian control procedures, followed by 13 sessions of cardiac conditioning under a delay paradigm. The conditional stimulus (CS) was a vertical line and the unconditional stimulus (US) was electric foot shock. Heart rate (HR) was analyzed in successive fivesecond intervals beginning five seconds before CS onset. The major finding was that the conditional response was consistently biphasic and consisted of an initial acceleration followed by deceleration toward the baseline, but rarely reaching it before onset of US. The subjects differed in magnitude of acceleration and subsequent deceleration as well as the location of the maximum rate in the CS-US interval. A breakdown of trials on the basis of the pre-CS HR revealed that the magnitude of effect was inversely related to the pre-CS rate.     

Varying temporal placement during CS of an added stimulus correlated with non-delivery of UCS

This experiment extends Pavlov’s method of contrasts for training a stimulus discrimination to the case of the cardiac conditional response in the rhesus monkey. It explores the parameter of temporal placement of an additional stimulus (“CS₂”) within a 10-sec CS (or “CS₁”), with the appearance of the former stimulus on any trial signalling the absence of UCS (electric shock) on that trial. This experimental paradigm is a parallel to that of the “intruded stimulus” studies in operant conditioning. In both cases, several ways of describing the function of the added stimulus are possible, but all seem reducible to the same operational terms. Data were taken in the present study with respect to the form and latency of the cardiac rate changes produced by intrusion of CS₂ (light), across a range of placements varying from simultaneity with CS₁ (a different light) onset to two sec before UCS would have been delivered. The control of CS₂ over the cardiac rate CR was occasionally exhibited with a latency as short as three beats after stimulus onset. The order of CS₂ temporal placements to which a subject was exposed was a factor in determining the form of the conditioned cardiac rate response to CS₁.     

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.     

Tactile conditioning of an autonomic and somatic response in young infants

Tactile classical conditioning of an autonomic reflex (pupillary dilation and constriction) and a somatic response (eyeblinking) was attempted in two separate experiments with one-month-old infants. The tactile CS was effective for conditioning eyeblinking but was ineffective for elaborating conditional pupillary reflex dilation or constriction. These differences were related to the interaction between stimulus and response in infant conditioning and the source of nervous system innervation of the CR as it relates to conditionability.     

An experimental study of the second-signaling systems of man through the printed language

The author has published previously in this journal his findings that not only the sight of a “pickled plum” increased the resting saliva of Japanese adults, but the spoken words “pickled plum” also increased the amount of saliva as a natural conditional reflex. It was also found that the reflex was stronger when an oral interpretation of the words “pickled plum” was added to their mere phonation. The author deduced that language is a conditional stimulus, the concept of which is released by unconditional stimulation. In this paper the author experimentally shows that reading printed language as well as writing it has the same effect in the human.     

Psychopharmacology and conditional reflexes

Drugs may be used in several ways to investigate their role in behavior. (1) The placebo effect is usually connected with the relation of the person to the drug. (2) Using the drug as an unconditional stimulus, its action may help to analyze the role of peripheral vs. central stimuli in the formation of conditional reflexes; our work has shown that the effect of drugs which act solely at the peripheral nerve endings without the involvement of the central nervous system cannot become conditioned. (3) The action of drugs on the conditional reflex (CR) compared with their action on the unconditional reflex (UR) explains some of their behavioral effects. (4) Schizokinesis is often prominent in the action of drugs. Although a drug may increase the level of the heart rate, for example, it can, on the other hand, diminish the reactivity shown in the CR. Meprobamate and mescaline affect differently the cardiac and the motor components of the CR, illustrating a schizokinesis. (5) The type of individual is an important factor in the action of drugs; the same drug may have opposite effects on different individuals. This leads to the conclusion that a drug should fit the individual as well as the disease. (6) Autokinesis is often seen in drug action. Therefore a single dose of some drugs, such as acetylcholine, epinephrine or LSD, may permanently change the relationships between excitation and inhibition, in the direction of improvement or deterioration (positive or negative autokinesis).     

Temporal pattern and spectral complexity as stimulus parameters for eliciting a cardiac orienting reflex in human fetuses

The purpose of this study was to determine whether temporal pattern and/or spectral complexity were important stimulus parameters for eliciting a cardiac orienting reflex (OR) in low-risk human fetuses. Each of 28 term fetuses was exposed to four sounds formed from the four different combinations of temporal pattern (pulsed, continuous) and spectral complexity (sine wave, /a/). The fetal cardiac electrical signal was captured transabdominally at a rate of 1024 Hz, and fetal R-waves were extracted by using adaptive signal-processing techniques. We found that pulsed sounds elicited a significantly greater decrease in heart rate (HR) than did continuous sounds. However, the HR response was relatively unaffected by spectral complexity. For the pure tone and the phoneme used in this study, our results indicate that temporal characteristics were more effective at eliciting a cardiac OR in human fetuses than was spectral complexity.     

Temporal pattern and spectral complexity as stimulus parameters for eliciting a cardiacorienting reflex inhuman fetuses

The purpose of this study was to determine whether temporal pattern and/or spectral complexity were important stimulus parameters for eliciting a cardiac orienting reflex (OR) in low-risk human fetuses. Each of 28 term fetuses was exposed to four sounds formed from the four different combinations of temporal pattern (pulsed, continuous) and spectral complexity (sine wave, IsJ). The fetal cardiac electrical signal was captured transabdominally at a rate of 1024 Hz, and fetal R-waves were extracted by using adaptive signal-processing techniques. We found that pulsed sounds elicited a significantly greater decrease in heart rate (HR) than did continuous sounds. However, the HR response was relatively unaffected by spectral complexity. For the pure tone and the phoneme used in this study, our results indicate that temporal characteristics were more effective at eliciting a cardiac OR in human fetuses than was spectral complexity.     

Use of the conditional reflex to assess the temporal characteristics of curarization effects on heart rate responding

A Pavlovian methodological counterpart to the use of druginduced changes in operant rates of responding was used to assess the temporal characteristics of d-tubocurarine chloride effects on the heart rate conditional reflex in rats. After a stable conditional reflex had been established, the base heart rate, as well as the unconditional and conditional reflex, was monitored during administration of the drug. A sizable behavioral effect was reflected in all three measures, including a temporary abolition of the conditional and unconditional reflexes. An interpretation of these results was discussed, and further development and application of this specific methodology was explored.     

Effects of pentobarbital sodium anesthesia and neurohumoral agents on the cardiac orienting reflex

Studies of the cardiac orienting reflex in 16 dogs, moderately anesthetized and awake are reported. In the anesthetized dogs prominent transient heart rate decrease was commonly noted within one or two beats after the onset of various auditory stimuli, and less often after visual stimuli. This cardiac inhibition was neither as prominent nor as frequent in occurrence in awake dogs. The respiratory cycle at stimulus onset influenced the appearance and degree of heart rate decrease, with the greatest and most frequent decreases occurring during the expiratory phase. Atropine abolished the response. There was little evidence of habituation of this orienting response under anesthesia, although “waxing” and “waning” apparently related to minute-by-minute fluctuations in degree of unconsciousness, occurred. These findings are discussed in relation to neurophysiological and neuroanatomical correlates of orienting responses, hypotheses of orienting and attention and cardiovascular neurohumoral mediators.