Stephen H. Hobbs

Operant performance of rats selectively bred for strong or weak acquisition of conditioned taste aversions

An ongoing program of selective breeding is successfully developing strains of Sprague-Dawley-derived rats that are strong or weak acquirers of a cyclophosphamide-induced taste aversion (TA). Although strain separation has been based exclusively upon the TA criterion, all subjects have also been studied with respect to the acquisition of shock-motivated environmental avoidance (SME A) responses. The separation of strains of strong and weak TA learners has not resulted in similar changes in SMEA learning efficiency. The present study was undertaken to extend this analysis by comparing the two strains on appetitively motivated operant behaviors. Both fixed-ratio (FR) and differential-reinforcement-of-low-rates (DRL) schedules were studied because of their respective contrast with and similarity to the TA paradigm. No strain differences in food-reinforced barpressing were detected under either the FR or the DRL schedule. These results indicate that strain separation on the basis of TA performance is not selecting for generalized learning or performance variables that are common to these tasks. However, in a finding that merits additional study, strong TA conditioners were found to satisfy a criterion for initial barpress acquisition under a continuous schedule of reinforcement in significantly fewer sessions than were required by the weak TA strain.

Taste aversion and passive avoidance in rats with hippocampal lesions

Rats with near total hippocampal lesions were compared with cortical and normal control animals on taste aversion and passive avoidance conditioning. While the initial magnitude of the taste aversion induced through illness was not significantly affected by hippocampal ablation, the aversion did extinguish more rapidly in experimental animals. Locomotor passive avoidance was significantly impaired by the lesion.

Taste aversion proneness: A modulator of conditioned consummatory aversions in rats

Sprague-Dawley-derived rats were sequentially conditioned to avoid both anise- and saccharin-flavored solutions with counterbalanced orders of flavor exposures prior to cyclophosphamide-induced illness. The amounts of saccharin and anise solutions consumed during separate postconditioning single-bottle tests were correlated to determine if aversion strength was consistent across flavors. The saccharin-anise sequence revealed a positive and significant correlation, supporting the hypothesis that conditioned flavor aversions are modulated by some intrasubject factor or factors, a tendency designated as taste aversion proneness. However, a correlational coefficient of marginal significance was obtained from the anise-saccharin sequence, leaving unanswered questions concerning the salience and generality of taste aversion proneness. Despite this limitation, taste aversion proneness is viewed as having important applied implications for aversion therapy approaches to the treatment of human alcoholism.

Temporal stability of psychophysiological response profiles: Analysis of individual response stereotypy and stimulus response specificity

Temporal stability of frontal electromyographic activity, hand surface temperature,and pulse were recorded from 64 subjects during four sessions over a months interval. Each session consisted of an adaptation period, a baseline condition, and two stressors (one cognitive, the other physical). Reliability coefficients on absolute scores across sessions were, for the most part, modest and statistically significant. Treating the responses as relative measures (percentage of change from baseline or simple change scores from baseline) produced smaller and less frequently significant correlation coefficients. The data were also examined in a multidimensional manner by using z-scores to determine if each subject showed any consistencies across sessions with respect to which response system was maximally aroused. This analysis led to identifying three groups of subjects: those who responded primarily within a single system across sessions regardless of stressor (individual response stereotypy, 42%), those who responded differentially across sessions to the two stressors (stimulus-response specificity, 20%), and those with profiles not readily classifiable (38%). Subjective ratings by clinicians showed little agreement with these classifications and poor reliability among raters was also obtained. The results are discussed in terms of their clinical implications.

Forgetting, preconditioning CS familiarization and taste aversion learning: An animal experiment with implications for alcoholism treatment ☆

Abstract The rapid taste aversion acquisition, which typically occurs in many species when ingestion of a novel flavor precedes gastrointestinal distress, is retarded by preconditioning familiarity with the CS flavor. This CS familiarity effect (CSFE) might contraindicate taste aversion approaches to alcoholism treatment since alcoholics are quite accustomed to the tastes of alcoholic beverages. However, many alcoholics do develop strong nausea—induced alcohol aversions under appropriate conditioning parameters. Additionally, the CSFE is attenuated in rats by repeated conditioning trials including discrimination training. The present animal experiment was conducted to determine if the CSFE could additionally be weakened by process of forgetting, i.e. by preconditioning withdrawal of a familiar flavor analogous to an alcoholics ‘drying out’ before psychotherapeutic intervention. Using saccharin as the CS flavor and cyclophosphamide as the conditioning agent, Sprague-Dawley derived rats acquired no aversions when conditioning was attempted immediately after flavor familiarization. However, significant and equivalent saccharin aversions were observed when conditioning was delayed for either 20 or 100 days after familiarization. These findings imply that the efficiency and cost effectiveness of taste aversion approaches to alcoholism treatment might be enhanced by a pretreatment period of abstinence from alcohol ingestion.

Differential olfactory bulb contributions to baitshyness and place avoidance learning.

Abstract Garcia and Ervin [14] hypothesized that neuroanatomically discrete associative mechanisms subserve illness-induced taste aversions and shock-motivated avoidance of telereceptive cues. Such neuroanatomical diversity implies that appropriately placed brain lesions might selectively influence one of these types of learning. While several limbic-system lesions can disrupt shock-motivated compartment avoidance (SMCA) without modifying illness-induced taste aversion (IITA) conditioning, the opposite pattern of selective interference has not been reported. The anterior tips of the olfactory bulbs of male albino rats were removed because neuroanatomical and behavioral data indicated that these lesions might disrupt IITA without influencing SMCA. Larger olfactory-bulb ablations approximating total bulbectomies were also studied for comparison purposes. Both total bulbectomies and anterior bulbectomies partially blocked IITA acquisition. Total bulbectomies also interfered with SMCA conditioning, but this learning was unimpaired by anterior bulbectomies. These anterior-bulbectomy results are consistent with the neuroanatomical-diversity hypothesis. Present findings are also discussed relative to the applied problem of selecting biologically appropriate noxious stimuli for aversion therapy approaches to alcoholism treatment.

Reliability of psychophysiological responding as a function of trait anxiety

This study examined the temporal stability of three psychophysiological responses (frontal electromyographic activity, hand surface temperature, and heart rate) recorded over four sessions (days 1, 2, 8, and 28) on 34 subjects, 17 with high Spielberger Trait Anxiety Inventory scores and 17 with low scores. Each session consisted of a 20-minute adaptation period, a baseline condition, and two stressors (one cognitive, the other physical). Two forms of reliability coefficients were employed, intraclass correlations and Pearson Product Moment; the two types of reliability coefficients arrived at the same conclusions. Results indicated that reliability coefficients for the two anxiety groups did not differ on frontal EMG or heart rate responses; however, hand surface temperature responding was considerably less reliable for high anxious individuals than low anxious individuals. Reliability coefficients on absolute scores were, for the most part, reliable. Treating the responses as relative measures (percent change from baseline or simple change scores from baseline) produced smaller and less reliable coefficients. Magnitudes of the three physiological responses did not significantly differ as a function of high or low trait anxiety. Findings are discussed in terms of their clinical, as well as basic psychophysiological, importance.

Taste-aversion conditioning in rats with septal lesions

Two experiments were conducted to assess the effects of lesions in the septal forebrain area of rats on the development and maintenance of a radiation-induced taste aversion. While the lesioned animals were found to drink more of the fluid used as a conditioned stimulus during X-radiation, no effect of the lesion on subsequent aversion to the stimulus was found. The data further restrict the generality of viewing the function of the septal forebrain area as inhibitory.

Illness-induced taste aversions in normal and bulbectomized hamsters

Abstract Baitshyness acquisition and extinction in male Syrian golden hamsters was evaluated using saccharin solution as the target flavor and 75 or 150 mg/kg injections of cyclophosphamide as the illness-inducing agent. Conditioned aversions were obtained in drug-injected animals, but extinction was rapid and complete within twelve days of two-bottle preference testing. A second experiment using the same animals found that bilateral aspiration of the olfactory bulbs disrupted the subsequent acquisition of an aversion to milk. Baitshyness appears to have advantages over other tasks producing avoidance behavior in the hamster, and the hamster may be useful in neural investigations of conditioned taste aversions which have previously concentrated on the rat.

Differences in cyclophosphamide-induced suppression of cricket predation in selectively bred strains of taste-aversion prone and resistant rats

Cyclophosphamide-induced conditioned suppression of cricket predation was observed in taste-aversion-prone (TAP) but not in taste-aversion-resistant (TAR) rats. These TAP and TAR strains had been selectively bred for efficient or inefficient acquisition of cyclophosphamide-induced saccharin taste aversions (TAs). Equivalent preconditioning cricket predation was practiced by nonfasted subjects of both strains. TAR rats that ate crickets before a cyclophosphamide injection were thereafter voracious predators as were saline-injected and pseudoconditioning controls of both strains. However, conditioned TAP rats subsequently displayed a marked suppression of cricket predation. Predation can provide a deprivation-free and species-natural consummatory response for studies of strain differences in TA conditionability of TAP and TAR rats. In addition, the present results indicate that TAP and TAR strain differences in TA conditionability are not restricted to the saccharin solution that was the conditioned stimulus basis of prior strain development.