Classical conditioning: The new hegemony

The development of anticipatory nausea in patients receiving adjuvant chemotherapy for breast cancer

Previous research on anticipatory nausea in cancer patients has focused on its occurrence in the clinic before chemotherapy infusions. The present study is the first, to our knowledge, to examine the development of anticipatory nausea across eight chemotherapy infusions for three time periods (night before, morning of, and immediately prior to each infusion). Based on classical conditioning experiments conducted with animal subjects, we hypothesized that the severity of anticipatory nausea would increase as the time for scheduled infusions approached. Eighty-two women diagnosed with Stage I or II breast cancer were assessed for the intensity of anticipatory nausea at three time periods prior to eight scheduled infusions of outpatient adjuvant chemotherapy. Analyses indicated a significant interaction between number of infusions experienced and temporal proximity to the infusion, supporting the hypothesis. Changes in the severity of anticipatory nausea across infusions were consistent with conditioned learning predictions. These results contribute to a growing recognition of the importance of conditioning principles for understanding side effects of chemotherapy for cancer and may have implications for the management of side effects secondary to a variety of pharmacotherapies in clinical practice.

Affective learning: awareness and aversion

In two studies, we investigated the influence of aversive and nonaversive reinforcers on startle reactivity, visceral responses, and self-report during Pavlovian conditioning. Furthermore, we assessed how awareness of the stimulus contingencies affect conditioned discrimination in the different response systems. Conditioned potentiation of the startle response was only observed in the context of aversive learning. Moreover, blink potentiation occurred without awareness of the relationship between the conditioned and unconditioned stimulus. In contrast, skin conductance conditioning was independent of the aversiveness of the reinforcer and was only obtained for those individuals who could correctly verbalize the stimulus contingency in a postconditioning recognition test. Cardiac responses varied with the task demands of the situation and covaried with individual response stereotypes.

Underestimating the rat's intelligence

Although rats are a much maligned species, it appears that their intelligence has been underestimated. This paper surveys evidence of cognition in rats from traditional categories (e.g. temporal and numerical competence) as well as from less ordinary test situations (e.g. transitive inference; recognition of individual humans). Although rats may not approach cognitive tasks using strategies observed in human subjects, they are frequently successful on their own terms. Indeed, rats are adept at exploiting procedural loopholes and confounded variables overlooked by human test designers. While not lending itself to the conventional classification of intelligence, this form of 'intellectual optimal foraging' may be an apt general description of the rat's cognitive prowess.

Conditioned reactions to cancer chemotherapy: percent reinforcement predicts anticipatory nausea

Current theorizing on classical conditioning has emphasized the role of contingent relations between the conditioned and unconditioned stimuli in the development of conditioned responses. The present study is the first to examine the relevance of this concept to our understanding of the phenomenon of anticipatory nausea in cancer chemotherapy patients. Anticipatory nausea in patients receiving emetogenic chemotherapy has been cited as an example of the importance of classical conditioning in clinical medicine. Outpatient chemotherapy can be viewed as a series of conditioning trials in which the previously neutral stimuli of the clinic (conditioned stimuli) are associated with chemotherapy infusions and postinfusion nausea. Reexposure to these clinic stimuli alone is sufficient to elicit nausea (conditioned response) in some patients prior to subsequent infusions. In the present study we examined whether differences among patients in percent reinforcement (the percentage of infusions followed by nausea) would predict anticipatory nausea, which was assessed at the sixth infusion. Results were consistent with the hypothesis. Percent reinforcement was positively correlated with the incidence of anticipatory nausea. Comparison of patients with and without anticipatory nausea (t-test and hierarchical logistic regression analysis) confirmed that percent reinforcement was a significant predictor of anticipatory nausea, independent of other factors previously reported to be involved.

Hypnosis treatment of clinical pain: understanding why hypnosis is useful

Clinical and experimental research literature indicates hypnosis is very useful for severe and persistent pain, yet reviews suggest hypnosis is not widely used. To encourage more widespread clinical application, the author reviews recent controlled clinical studies in which hypnosis compares favorably with other interventions; links advances in understanding endogenous pain modulation to a neurophysiologic view of hypnosis and hypnoanalgesia; relates the neurophysiology of hypnoanalgesia to management of chronic pain; challenges the view that hypnotic pain control is only for the highly hypnotizable patient; and raises issues about how people learn to control pain with hypnosis. Training in hypnotic analgesia may usefully enhance nervous system inhibitory processes that attenuate pain.

The conditioning of human sexual arousal

Although most theories of human sexual behavior claim that much normal sexual behavior is learned, and theories of the etiology and modification of paraphilic and dysfunctional sexual behavior also claim that abnormal sexual behavior is learned and can be counterconditioned, there is no systematic review examining the relationship between conditioning and human sexual behavior. We review research addressing whether habituation, sensitization, classical conditioning, and operant conditioning processes are involved in human sexual behavior. We conclude that, due to the methodological problems of extant studies, the basis for asserting the existence of relationships between habituation, sensitization, classical conditioning, operant conditioning, and sexual behavior is tenuous.

Alcohol in the amniotic fluid prior to cesarean delivery: effects of subsequent exposure to the drug's odor upon alcohol responsiveness

Rat fetuses during the last day of gestation have the capacity to process ethanol and non-ethanol-related chemosensory cues present in the amniotic fluid. Recent studies suggest that the consequences related to cesarean delivery act as an unconditioned stimulus that is associated with these cues. In the first experiment, ethanol neonatal responsiveness assessed through a motor activity test was analyzed in pups that received ethanol or saline in utero proximal to cesarean delivery. Different factors and the interaction among them, were analyzed in this experiment: (i) ethanol concentration administered into the amniotic sac (0, 6, or 18% v/v), (ii) delay between administration and cesarean section (3, 10, or 30 min), and (iii) postnatal exposure to ethanol odor prior to test (0, 7.5, or 15 min). Only animals exposed to ethanol 10 min prior to delivery differed from vehicle-exposed subjects. Subsequent postnatal exposure to ethanol odor attenuated the magnitude of prenatally established effects. In the second experiment it was observed that prenatal ethanol exposure was sufficient to increase ethanol intake during Postnatal Day 11. Again, this effect was strongly attenuated when pups were exposed to the odor of the drug prior to assessment procedures. These results suggest that (i) associations between chemosensory cues in the amniotic fluid and consequences related with perinatal manipulations are likely to occur and (ii) postnatal reexposure to similar cues exerts an effect comparable to an extinction phenomenon.

Reflections on human Pavlovian decelerative heart-rate conditioning with negative tilt as US: alternative approaches

The negative-tilt preparation that has been reported since the late seventies is a specific form of Pavlovian conditioning that is of scientific interest and has potential applications. In this paper I reflect on the usefulness, to the development of this preparation, of two approaches to Pavlovian conditioning. One approach is the older S-R learning, stimulus-substitution paradigm exemplified by learning texts of the sixties. The other is the modern, Tolman-like view, according to which the phenomenon of Pavlovian conditioning is "now described as the learning of relations among events so as to allow the organism to represent its environment." The three assumptions encapsulated by this approach are: (a) that only CS-US contingency relations are learned; (b) that teleological modes of explanations are adequate; (c) that the representational theory of knowledge is sound. Concerning Pavlovian conditioning in general, questions been raised in the literature for all three assumptions; they have not been adequately answered. Regarding the specific problem of developing the human Pavlovian heart-rate decelerative conditioning with negative tilt as the US, I suggest that the cognitive approach has been much less helpful than the older, S-R, stimulus-substitution paradigm. Nevertheless, other literature clearly indicates that the cognitive, S-S approach has generated considerable interest and research, especially in preparations like the conditioned emotional response (CER), which are CS-IR ones in the sense that the effects on the CR are assessed indirectly through measuring an indicator or instrumental response (IR).(ABSTRACT TRUNCATED AT 250 WORDS)

Temporal characteristics of appetitive stimulus effects of luteinizing hormone-releasing hormone in male rats

Conditioned place preference, induced by intraperitoneal injections of 5 micrograms/kg luteinizing hormone-releasing hormone (LHRH), was studied by varying the interval between the injection of LHRH and the conditioning sessions. Place preference was investigated for five presession intervals (0, 15, 45, 75, and 120 min) in separate groups of gonadectomized male rats provided with a subcutaneous testosterone implant. It was shown that the presession interval is an important parameter in the development of LHRH-induced conditioned place preference. Place preference was not observed after conditioning with intervals of 0, 75, and 120 min. With 15 and 45 min, however, a reliable preference was induced by LHRH. This study provides insight into the onset and offset of the appetitive stimulus properties of LHRH in male rats.

Estradiol-induced conditioned taste aversion and place aversion in rats: sex- and dose-dependent effects

Effects of various doses (0-250 micrograms/kg, SC) of estradiol-17 beta (E2) in a two-bottle choice conditioned taste aversion and a two-compartment conditioned place preference procedure were studied in male and female rats. Dose-dependent taste aversion and place aversion effects of E2 were established, and the conditioned taste aversion procedure was found to be more sensitive in detecting aversive properties of E2 than the conditioned place preference procedure. Although aversive properties of E2 were found in both sexes, the effects were clearly more prominent in males as compared to females. From this study, it was concluded that E2 acts as an unconditioned aversive stimulus in both male and female rats capable of gaining control over different types of behavior by associative learning.

Association between chemosensory stimuli and cesarean delivery in rat fetuses: neonatal presentation of similar stimuli increases motor activity

Recent studies conducted in this laboratory indicated that prenatal chemosensory stimulation followed by cesarean delivery strongly affected postnatal responsiveness to odors derived from the administered substances. The present experiments were performed in order to examine if an associative process was responsible for such effects. In Experiment 1 rat fetuses during Gestational Day 21 were exposed to a tenuous alcohol solution or to a lemon-containing solution either 40 or 10 min prior to cesarean delivery. All subjects were subsequently tested in terms of changes in neonatal motor activity when confronted with the odor of alcohol or lemon. Rats experiencing prenatal cues 10 min prior to delivery exhibited higher and differential responsiveness to the smell of these cues when compared to those experiencing similar solutions 40 min prior to delivery. In Experiment 2 each fetus sequentially experienced both cues. Subsequent tests confirmed that the delay between prenatal sensory experience and birth induction was critical in terms of significantly affecting olfactory-mediated motor responses. The results suggest that consequences related with cesarean delivery act as an unconditioned stimulus capable of being associated with orosensory cues present in the amniotic fluid.

Conditioned opponent processes in the development of tolerance to psychoactive drugs

1. Tolerance may involve classical conditioning processes. A conditioned drug-opponent response is thought to increase with drug exposures and summate with the unconditioned response to the drug - resulting in tolerance. 2. Support for this theory comes from reports that tolerance exhibits many basic features of classical conditioning phenomena. 3. Problems for this account of tolerance arise from the fact that some, but not all, empirical attempts to demonstrate conditioned opponent responses have failed. 4. It has consequently been suggested that tolerance might best be conceptualised in terms of theories of habituation, which do not involve opponent processes. 5. The controversy over the role of opponent processes is theoretically important, because conditioned opponent processes are believed to be involved in dependence. Resolution of the controversy requires that parametric studies are conducted, in which the optimal conditions for obtaining conditioned tolerance are defined, and an efficient "model system" developed for analysis of the possible role of opponent processes in tolerance. 6. Research in this area highlights the importance of interdisciplinary studies of tolerance and dependence.