Discrimination between aversive brain stimulations: effect of stimulation parameters

Rats placed in a T maze were shown to be able to discriminate between two stimulations applied to one and the same brain site and inducing aversive effects of different magnitude. Discrimination occurred irrespective of whether the two stimulations differed in either intensity or frequency, and irrespective of whether they were applied to a medial hypothalamic or to a mesencephalic central gray site. Generalization experiments were performed in which either the stimulation parameter used to establish the discrimination or another parameter was varied. The results show that the animal's choice cannot be predicted on the sole basis of either the electrical charge/second applied or the escape latency induced.     

Direction of human motor responses by men and women to aversive stimulation

The frequency of extensions and flexions of the arms of 12 men and 12 women (ages 20-30 years) responding to a neutral tone or to an electric shock was recorded. Subjects had to choose between pushing or pulling a lever upon receipt of an acoustic signal which was paired or unpaired with an electric shock. They were instructed to perform either long duration movements, allowing for on-line control of the execution, or short duration movements with prior specification of amplitude. Regardless of duration of movements, the aversive signal increased the frequency of extensions and intraindividual variability of choices of the men but decreased the frequency of extensions and intraindividual variability of choices of the women. These findings show that stimuli such as pain or fear automatically elicit patterns of terminal motor states corresponding to fight or flight, initiating processes of preparation of spatially oriented movements which are automatic and sex-typed and impair the use of the terminal cues for simultaneous preprogrammed voluntary movements.     

Reflexive fighting in response to aversive stimulation

Reflexive fighting was elicited between paired rats as a reflex reaction to electric shock prior to any specific conditioning. Such fighting was fairly stereotyped and easily differentiated from the rats' usual behavior. The strength of this reflex was not attributable to any apparent operant reinforcement. Elicitation of fighting was a direct function of the enclosed floor area and a nonmonotonic function of the shock intensity.

Failure to scramble the polarity of the electrified grid produced inconsistent fighting. Under optimal conditions fighting was consistently elicited by shock regardless of the rat's sex, strain, previous familiarity with each other, or the number present during shock. Repeated shock presentations did not produce an appreciable decrease in fighting until signs of physical debility appeared. Although shock did not cause a rat to attack inanimate objects, it did produce attack movements toward other small animals. Failure of guinea pigs to defend themselves revealed that the elicitation of fighting from the rat does not require reciprocal attack. Paired hamsters showed fighting reactions similar to those of the rats, whereas guinea pigs failed to fight. Electrode shock and a heated floor elicited fighting between the rats, but intense noise and a cooled floor did not.

     

Response cost and the aversive control of human operant behavior

The effects of cost (point-loss per response) upon human avoidance, escape, and avoidance-escape behavior maintained by PLPs (point-loss periods) were investigated. Cost had a marked but differentially suppressive effect upon responding under all schedules. The greatest number of PLPs taken under cost occurred on the escape schedule. In most instances PLPs were more frequent on the avoidance-escape schedule than on the avoidance schedule under cost. Inferior avoidance performance appeared only under cost conditions. Under no-cost, all subjects (Ss) successfully avoided all PLPs after the first hour of conditioning. These results indicate that the development and maintenance of human avoidance and escape behavior may, in part, be dependent upon response cost conditions. Aversive control of human operant behavior may be limited without an adequate specification of response-cost conditions.     

Classical aversive conditioning of heart rate in curarized rats at different blood gas levels

In an effort to examine whether normal blood gas tensions were essential for conditioning, paralyzed rats received a classical aversive heart rate (HR) conditioning session while respirated at different peak expired CO₃ values. After the session, arterial blood was drawn for analysis. That peak expired CO₂ was effective in manipulating Pco₂ was indicated by a significant correlation (r = 0.594, df = 17, P < 0.05). In addition, only rats with blood gas values similar to those of anesthetized controls displayed a discriminated HR CR. These animals also had lower baseline HRs and greater HR variability. Further, 7 of the 9 rats with normal blood gas values were respirated at peak expired CO₂ values from 5.0–5.1 per cent, and no animal ventilated within this range displayed abnormal values. These findings suggest that previous difficulties in obtaining classical and operant conditioning in paralyzed animals may, in part, be attributable to inadequate ventilation.     

Avoidant control difficulty and aversive incentive appraisals: Additional evidence of an energization effect

There is evidence that certain physiological and subjective indices of stress are relatively great when control over aversive outcomes is moderately difficult and relatively reduced when control over such outcomes is either easy or impossible. A possible explanation is suggested by Brehm's recent theory of motivation, which asserts that energy mobilization and the perceived unpleasantness of an aversive event will (a) increase with the difficulty of avoidant behavior so long as avoidance is believed to be possible and worthwhile, and (b) be low when avoidant behavior is impossible, not worthwhile, or simply unavailable. This article reports two experiments that examined appraisals of an aversive incentive under conditions where avoidance was expected to be easy, difficult, and impossible. The first demonstrated the complete nonmonotonic pattern of appraisals predicted by the energization theory, something that has proved elusive in previous investigations. The second study demonstrated this as well and, in addition, showed a correspondence between subjects' incentive appraisals and their cardiovascular responses immediately before and during an avoidance task period. Implications and alternative interpretations are discussed.This research was supported in part by a Faculty Research Award from the University of Alabama at Birmingham.     

Note on relation of autonomic perception to voluntary control of heart rate.

Relationships between subscores of the Autonomic Perception Questionnaire and ability to raise and lower heart rate voluntarily were examined in 40 subjects. Subscores which reflected autonomic awareness in anxiety and pleasure states were not predictive of degree of cardiac control, while the subscore specific to reported awareness of heart functioning during pleasure states only was positively correlated with ability to raise heart rate.     

Postnatal development of heart rate patterns elicited by an aversive CS and US in cats

Heart rate and motor responses were recorded in cats of different ages during classical conditioning. A deceleratory-acceleratory heart rate pattern observed during the CS-US interval in one and four-week-old kittens is an alpha conditioned response, a potentiated original response to the CS. At eight weeks of age two new distinct patterns of pure acceleration or pure deceleration are acquired during conditioning and in the absence of motor learning. At 12 weeks of age and in adult subjects, heart rate patterns during the CS-US interval become more complex and conditioned motor responses can be observed. A covariance of HR acceleration and motor responses during the CS-US interval is absent in eight-week-old subjects, but quite high in 12-week-old subjects and adult cats. The data are interpreted as suggesting separate elicitatory mechanisms of HR and motor responses which may show synchrony later in ontogeny.     

Human motor responses to simultaneous aversive stimulation and failure on a valued task

The effects of presentation of an aversive stimulus and simultaneous failure on a bogus intelligence test upon a subject's aggressive reactions were studied. The subject's fist clenching was used as an indicator of aggression. Four conditions, generated by the combinations of two kinds of stimulus delivered to the subjects (aversive or nonaversive) and two outcomes of the task (failure or success), were investigated. 20 female and 20 male students (ages: 17-34 years) were instructed, upon the reception of an aversive or nonaversive acoustic signal, to press with the right hand a device that displayed a slide. Each slide presented an item from an intelligence test, to which the subjects were either allowed to answer successfully (success) or not (failure). Failure increased the subject's autonomic arousal, as measured by photoplethysmographic sensors, in all stimulation conditions, but only the condition with aversive stimulation increased the speed of clenching. This was interpreted as indicating subject's tendencies to aggression. These results are discussed in relation to the effects of frustration.