Conditioned suppression to odorous stimuli in the rat.

Used a modified conditioned-suppression technique to train 6 male Sprague-Dawley rats to criterion discrimination of amyl acetate at 10-2.0 of vapor saturation. The magnitude of suppression was also recorded as a function of concentration and amyl acetate, with the concentrations presented by the method of constant stimuli. Amyl acetate thresholds were 10-5.50, 10-5.25, 10-5.70, 10-5.75, 10-5.90, and 10-5.80 of vapor saturation for the Ss. Mean thresholds for butyl, amyl, hexyl, and heptyl acetates were also determined. An independent measurement of the amyl acetate concentrations determined by the olfactometer was made with gas-liquid chromatography. Results indicate that the methodology employed is accurate for a 6 log unit range. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned taste aversion and specific need states in the rat.

In 3 experiments, a total of 151 female Wistar rats were allowed to consume either sucrose or saline prior to being made ill by injection of either insulin or formalin, or by exposure to X rays. A 2-bottle preference test between sucrose and saline revealed that formalin was an effective agent in conditioned aversions to sucrose but not to saline. Similarly, injections of insulin were effective in producing conditioned aversions to saline but not to sucrose. X-irradiation produced strong aversions to either solution. Results are discussed with regard to the specific need states that insulin and formalin produce. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned suppression of distress calls in imprinted ducklings.

Exposed 20 Peking and 6 Khaki Campbell newly hatched ducklings to imprinting procedures. The subsequent filial reactions were studied using a classical conditioning paradigm. Exp. I revealed that a previously neutral stimulus can become a conditioned suppressor of distress calling as a consequence of pairing it with the imprinted stimulus. If the presentation of the imprinted stimulus was, however, omitted or delayed, or if it preceded rather than followed the presentation of the neutral stimulus, the effect was not obtained. Exp. II utilized a differential conditioning procedure to investigate the capacity of imprinted Ss to come under discriminative control. 2 differently colored lights were used as stimuli; 1 was consistently followed by presentation of the imprinted stimulus, while the other was never followed by its presentation. Only the former stimulus came to suppress distress calling. The importance of the apparent interaction between classical conditioning and imprinting is noted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned cyclosporine effects but not conditioned taste aversion in immunized rats.

In 2 experiments, the development of adjuvant arthritis (an experimental autoimmune disease) was inhibited by exposing rats to a flavored solution that had previously been paired with injections of cyclosporine (an immunodepressive drug) compared with rats with the same history but exposed to a flavored solution that had previously not been paired with drug injections. In contrast to earlier experiments on conditioned cyclophosphamide effects, rats did not avoid the taste that had previously been paired with drug administration. Thus, conditioned immunopharmacologic effects were not confounded with taste aversion. These observations are interpreted as reflecting an associative learning process that affected the development of an autoimmmune disease. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned antisickness: Heat as an internal stimulus in conditioning taste aversion and aversion failure in rats.

Heat was found to be effective as a conditional stimulus in the aversion failure procedure (S. Revusky et al; see record 1980-27581-001) and was also found to be effective as an unconditional stimulus using a taste aversion procedure in which rats exposed to high ambient temperature following saccharin consumption showed robust saccharin aversions relative to unpaired and unheated controls. The antisickness and taste aversion conditioning evidence force reexamination of the view that toxic heat effects are referred to the external environment. Together with other recent evidence from this laboratory, these data support the hypothetical antisickness mechanism of aversion failure, which requires that toxic heat serve as an internal stimulus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned flavor preference and aversion: Role of the lateral hypothalamus.

Food-restricted rats with ibotenic acid lesions of the lateral hypothalamus (LH) and sham controls were trained to associate flavored solutions with positive or negative postingestive consequences. The LH rats learned to prefer a flavor that was paired with concurrent intragastric infusions of maltodextrin. Unlike controls, the LH rats failed to learn a preference for a flavor paired with delayed maltodextrin infusions and showed an attenuated preference for a flavor paired with concurrent fat infusions. The LH rats did not differ from controls in learning to avoid flavors paired with concurrent or delayed infusions of lithium chloride. These data indicate that the LH is not essential for all types of flavor-postingestive consequence conditioning but is critical for learning to associate flavors with delayed nutrient feedback. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned emotional distress in women receiving chemotherapy for breast cancer.

This study investigated whether women undergoing outpatient chemotherapy for breast cancer can develop classically conditioned emotional distress. Women scheduled to begin chemotherapy were randomly assigned either to an experimental group (exposed to a distinctive stimulus before each chemotherapy infusion) or a control group. After repeated infusions of chemotherapy, patients' responses to the distinctive stimulus were assessed in a location not associated with chemotherapy administration. At the test trial, experimental group patients showed evidence of increased emotional distress (self-reported on a visual analog scale) after the presentation of the distinctive stimulus, whereas control group patients did not. Post hoc analyses indicated that these increases in distress were not secondary to other conditioned responses (e.g., nausea, taste aversion). Thus, results supported the hypothesis that the pairing of a distinctive stimulus with chemotherapy would result in the development of a conditioned emotional response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned taste aversion in lean and obese rats with ventromedial hypothalamic knife cuts.

Assessed the development of a conditioned taste aversion (CTA) in 60 female Sprague-Dawley rats made hyperphagic with parasagittal knife cuts in the ventromedial hypothalamus (VMH). Ss were water deprived and presented with a .1% saccharin solution paired with injections of either LiCl or NaCl. In Exp I, VMH Ss tested at a nonobese weight level did not differ from sham-operated controls in acquisition and extinction of the CTA. In Exp II, moderately obese VMH Ss displayed a stronger CTA than did sham-operated controls as evidenced by slower extinction. A 2nd group of obese VMH Ss given an amount of LiCl equivalent to that given to the controls also displayed retarded extinction of the CTA. Results reflect an obesity-induced suppression in appetitive motivation. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the automatic nature of phobic fear: Conditioned electrodermal responses to masked fear-relevant stimuli.

Normal Ss (n?=?64) were exposed either to pictures of snakes and spiders or to pictures of flowers and mushrooms in a differential conditioning paradigm in which one of the pictures signaled an electric shock. In a subsequent extinction series, these stimuli were presented backwardly masked by another stimulus for half of the Ss, whereas the other half received nonmasked extinction. In support of a hypothesis that suggests that nonconscious information-processing mechanisms are sufficient to activate responses to fear-relevant stimuli, differential skin conductance response to masked conditioning and control stimuli was obvious only for Ss conditioned to fear-relevant stimuli. These results were replicated in a 2nd experiment (n?=?32), which also demonstrated that the effect was unaffected by which visual half-field was used for stimulus presentation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exposure to novel environmental stimuli decreases amphetamine self-administration in rats.

Researchers examined whether exposure to novel environmental stimuli reduces drug self-administration. Rats were trained to self-administer amphetamine on a fixed ratio (FR) 5 schedule of reinforcement and then were exposed to novel stimuli during the session. Responding was significantly decreased with exposure to novelty but returned to baseline levels on intervening nonexposure sessions. In 2 subsequent experiments, rats were exposed to novel plastic objects prior to the session. Immediately following exposure, rats were allowed to self-administer amphetamine on an FR 1 schedule, which was increased gradually to an FR 5 either using predetermined increments or on the basis of performance criteria. Exposure to the novel objects significantly decreased acquisition of amphetamine self-administration in both situations. Results suggest that exposure to novel environmental stimuli may be effective at reducing drug self-administration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modification of unit responses to gustatory stimuli by conditioned taste aversion in rats

Secretion of trypsin, chymotrypsin, lipase and amylase was measured in male rats under urethane anaesthesia using a method of continuous perfusion of the duodenum. Prolonged infusion of cholecystokinin-pancreozymin (CCK-PZ) over a period lasting 200-360 min was administered either alone or together with a submaximal dose of secretin (1 unit/100 g - 10 min). Infusion of CCK-PZ was carried out using maximal doses (1--1.5 unit/100 g - 10 min) with and without secretin. Supramaximal doses of CCK-PZ (2 and 4 units/100 g - 10 min) were used only in combination with secretin. In all experiments secretion of enzymes showed a triphasic pattern including an initial peak followed by a plateau secretion after 10--20 min (phase 1), a decreasing second phase and finally base-line secretion (phase 3), thus demonstrating exhaustion of enzyme output from the gland with time. With increasing and supramaximal dose of CCK-PZ the cumulative output of enzymes from start to baseline secretion decreased progressively. Under the same conditions the levels of peak and plateau secretion were lower, the duration of plateau secretion was longer and the decreasing phase of secretion was shortened. These features indicate inhibition of secretion with increasing supramaximal doses of CCK-PZ infusion. Whereas the proteolytic enzymes and lipase reacted in a parallel way always amylase secretion was sustained on a higher level, implicating an alternative pathway for secretion.     

Conditioned taste aversion is disrupted by prolonged retrograde effects of intracerebral injection of tetrodotoxin in rats.

Acquisition of conditioned taste aversion (CTA) is disrupted when 10 ng tetrodotoxin (TTX) is injected into both parabrachial nuclei of rats immediately after saccharin drinking and before LiCl poisoning (S. F. Ivanova & J. Bure?, in press). Further analysis of this finding showed that parabrachial TTX injection (1) elicited retrograde amnesia also when applied 1, 2, or 4 days but not 8 days after CTA acquisition; (2) did not abolish CTA produced by 2 or 3 saccharin–LiCl pairings; (3) did not cause persistent increase of quinine threshold; and (4) elicited anterograde CTA amnesia when applied 1 but not 2, 4, or 8 days before CTA acquisition. TTX-induced amnesia is not due to persistent gustatory agnosia but rather to disruption of the protracted consolidation of the permanent CTA engram by prolonged cessation of impulse activity in the information storing network. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of noxious environmental stimuli on vigilance.

12 Ss in an army troop carrier were asked to detect and respond to obscure, randomly occurring signals under each of 4 field conditions: control—stationary vehicle, moderate noise and heat; moderate heat, noise, vibration (moving vehicle); intense heat, moderate noise, stationary vehicle; vibration (moving vehicle), high heat and noise. "Noise and vibration produced by the moving vehicle appreciably increased the median response times of the Ss. Further decrement occurred when heat was combined with noise and vibration, but the effect was relatively transitory. Heat alone had no apparent effect. Changes occurring as a function of elapsed time were not apparent." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of nutritive and nonnutritive stimuli in intestinal and oral conditioned taste aversion paradigms.

The intestinal taste aversion paradigm has previously demonstrated that animals could orally discriminate between carbohydrate and fat subsequent to pairing a gastrointestinal (GI) infusion of 1 nutrient with lithium chloride (LiCl), whereas they could not discriminate between 2 nonnutritive flavors (A. L. Tracy, R. J. Phillips, M. M. Chi, T. L. Powley, & T. L. Davidson, 2004). The present experiments assessed the relative salience of nutritive and nonnutritive stimuli when presented either intestinally or orally. Two compound stimuli, each comprising 1 nutrient and 1 nonnutritive flavor, were presented in training and were paired with LiCl or saline. Subsequent oral intake of the nutrients alone, the flavors alone, or the compounds was measured. Results showed that rats discriminated both nutrients and flavors independently after GI or oral training, whereas the compounds were discriminated only after oral training, indicating substantive differences in the processing of these stimuli. This suggests that nutrient activation of the GI tract may potentiate learning about nonnutritive flavors analogously to taste-potentiated odor conditioning. The ability to learn about the oral properties of stimuli in the GI tract suggests a new account of delayed taste aversion learning as well as learning about the positive nutritive consequences of food consumption. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Functionally distinct memories for imprinting stimuli: Behavioral and neural dissociations.

Precocial chicks exposed to a stimulus subsequently approach that stimulus in preference to other, novel stimuli. Previous investigations of the neural basis of these imprinting preferences suggest that imprinting training results in the formation of two memories. The first memory is formed rapidly and is located in the intermediate and medial part of the hyperstriatum ventrale (IMHV) of the left hemisphere; the formation of the second, in another memory system, S', takes several hours and can be prevented by a lesion placed in the right IMHV soon after training. The results of the present study suggest that the functional characteristics of these memories differ. Although memories in both left IMHV and S' supported imprinting preferences (Experiments 1a and 2a), only memories in S' influenced the acquisition of a heat-reinforced discrimination in which imprinted objects served as discriminanda (Experiments 1b and 2b). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned flavor aversions to familiar tap water in rats: An adjustment with implications for aversion therapy treatment of alcoholism and obesity.

Notes that conditioned flavor aversions, readily established in rats by pairing a novel palatable flavor with radiation-induced or drug-induced illness, are highly efficient adjustments with implications for the treatment of alcoholism and obesity. Recent experiments show that such aversion acquisition is diminished by preconditioning familiarity with the conditioned stimulus (CS) flavor. However, these studies involved single pairings of the target flavor with postingestional illness. In the present experiment with Sprague-Dawley-derived male rats, multiple conditioning trials and discrimination training were combined to produce a marked aversion to a highly familiar and relatively bland substance, plain tap water. This conditioned water aversion demonstrates the transient nature of the CS familiarity effect, thus weakening any contention that preconditioning exposure to target flavors will necessarily render aversion therapy for alcoholism or obesity ineffective. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ontogeny of behavioral arousal: The role of environmental stimuli.

During the course of ontogenesis the developing rat has been reported to pass through a transient period of intense behavioral arousal which peaks at 15 days of age, a phenomenon that has been interpreted to reflect a sequential caudal to rostral development of excitatory and inhibitory systems in the mammalian brain. In the present 4 experiments with male and female Sprague-Dawley rats, it was shown that (a) this period of intense hyperactivity occurred only when the animal was tested alone in an unfamiliar environment, the degree of arousal was proportional to the dissimilarity between the home cage and the test environment, and isolation per se was insufficient to elicit the arousal response; (b) environmental temperature had a minimal influence on the degree of behavioral arousal in either familiar or unfamiliar environments; (c) unlearned responses to pheromonal or other naturally occurring nest odors did not suppress the high levels of locomotor activity evoked by unfamiliar environments in the 15-day-old rat pup; and (d) it is fear or distress evoked by the unfamiliar environment rather than curiosity that underlies this developmental phenomenon. It is concluded that the sequential increase and decrease in locomotor activity that occurs during ontogenesis cannot be used to support the principle of caudal to rostral development of excitatory and inhibitory centers in the CNS. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Blindness to response-compatible stimuli.

This contribution is devoted to the question of whether action-control processes may be demonstrated to influence perception. This influence is predicted from a framework in which stimulus processing and action control are assumed to share common codes, thus possibly interfering with each other. In 5 experiments, a paradigm was used that required a motor action during the presentation of a stimulus. The participants were presented with masked right- or left-pointing arrows shortly before executing an already prepared left or right keypress response. We found that the identification probability of the arrow was reduced when the to-be-executed reaction was compatible with the presented arrow. For example, the perception of a right-pointing arrow was impaired when presented during the execution of a right response as compared with that of a left response. The theoretical implications of this finding as well as its relation to other, seemingly similar phenomena (repetition blindness, inhibition of return, psychological refractory period) are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioning to complex stimuli.

A research program is described dealing with behavior in a classical GSR conditioning situation. The empirical program is related "to the broader perspective of psychology in general." The research "affords a slim—but I hope stable—bridge between S-R learning theory and whatever is meant by perceptual theory." A rationale of assumptions is developed and on the basis of analysis predictions are formulated. "The present results are eminently consonant with an S-S interpretation of behavior… though I have attempted to make it consonant with S-R contiguity theory by employing the notion of internalized stimuli generated by responses to the conditioned stimulus." (PsycINFO Database Record (c) 2010 APA, all rights reserved)