Conditioned nausea in rats: Assessment by conditioned disgust reactions, rather than conditioned taste avoidance

The terms conditioned taste avoidance and conditioned taste aversion are often used interchangeably in the literature; however, considerable evidence indicates that they may represent different processes. Conditioned taste avoidance is measured by the amount that a rat drinks in a consumption test that includes both appetitive phases and consummatory phases of responding. However, conditioned taste aversion is more directly assessed using the taste reactivity (TR) test that includes only the consummatory phase of responding. Rats display a conditioned taste aversion as conditioned disgust reactions (gapes, chin rubs, and paw treads) during an intraoral infusion of a nausea-paired flavored solution. Only treatments that produce nausea produce conditioned disgust reactions, but even rewarding drugs produce conditioned taste avoidance. Furthermore, treatments that alleviate nausea prevent the establishment and the expression of conditioned disgust reactions, but they do not necessarily modify conditioned taste avoidance. Considerable evidence exists indicating that these two measures can be independent of one another. The potential of a compound to produce conditioned disgust reactions is a reflection of its nausea-inducing properties. Taste avoidance may be motivated by conditioned fear rather than conditioned nausea, but conditioned disgust is motivated by conditioned nausea. (PsycINFO Database Record (c) 2008 APA, all rights reserved).     

Justice concept development as shown in reward allocations

Ss at six age levels (range 7–22 years) were asked to allocate rewards to two actors in tasks which showed differences in number of actors' products, actors' effort, actors' relative contributions, and the logical relation of actors' contributions, respectively. Contrary both to Adams' and Piaget's justice theories, results showed a greater variation in allocations for tasks than for age. Equal allocations of reward were most frequent when actors' effort and relative contributions were different, unequal allocations were most frequent for differences in actors' products, and for differences in logical relation of contributions. Equal reward allocations were furthermore more frequent when responses were related to the shared rather than the individual aspect of actors' contributions, and when there was a personal relationship between actors.     

Conditioned aversions and their memories in 5-day-old rats during suckling

Association learning during suckling was investigated. Five-day-old rats equipped with tongue cannulae placed either 2 mm rostral or 4-6 mm caudal to the intermolar eminence received sweet or salty solutions while suckling. This ingestion was followed by lithium chloride toxicosis. Pups with anterior cannulae took in considerably less fluid than control pups when tested 5 or 16 days later. A series of control groups demonstrated that this acquired aversion was associative in nature. Pups with posterior cannulae did not form the association. The failure of 5-day-old rats with posterior cannulae to form associations while suckling is not due to the prevention of conditioning by the act of suckling per se. Rather, the failure rests in the fluid's not reaching anterior taste receptors when injected into the posterior oropharynx, where the nipple normally empties its contents. These findings are discussed in terms of the transfer of information obtained during suckling prior to weaning, to feeding and drinking during and after weaning.     

Conditioned memory modulation, freezing, and avoidance as measures of amygdala-mediated conditioned fear

Three conditioned aversive responses were used to infer the existence of an unobservable central state of "conditioned fear," and the roles of certain amygdala subregions in producing these responses were investigated. Rats received tone-shock pairings in one compartment of a shuttle box and no tones or shocks in the other, distinctive, compartment. They were then trained to find food in one arm of a Y-maze. After the final training trial they were exposed to different sets of stimuli in the shuttle box with no shock. Twenty-four hours later rats that had received immediate posttraining exposure to the conditioned stimuli (in the shock-paired compartment) made significantly more correct responses on the Y-maze than rats that had been exposed to the neutral stimuli (in the no-shock compartment) or rats that had received delayed posttraining exposure to the conditioned stimuli. This constitutes a demonstration of posttraining memory modulation by conditioned aversive stimuli. Freezing increased during posttraining exposure to the conditioned stimuli compared to the neutral stimuli. When subsequently allowed to move freely between the two compartments, the rats in all groups also showed significant conditioned avoidance of the compartment containing the conditioned stimuli. In a second experiment the effects of lesions confined to specific parts of the amygdala on the three conditioned responses (memory modulation, freezing, avoidance) were tested. Lesions of the central nucleus impaired all three conditioned responses; lesions of the medial nucleus impaired conditioned modulation and avoidance. These lesions had no effect on freezing during the training trials. Lesions of the lateral and basolateral nuclei attenuated freezing during both training and testing. The findings suggest that the central and medial nuclei of the amygdala may be important parts of neural circuits mediating conditioned responses that constitute conditioned aversive states, but that conditioned freezing may be mediated independently.     

The motor side of emotions: investigating the relationship between hemispheres, motor reactions and emotional stimuli

The aim of the present study was to analyze if the left hemisphere preferentially controls flexion responses toward positive stimuli, while the right hemisphere is specialized toward extensor responses to negative pictures. To this end, right-handed subjects had to pull or push a joystick subsequent to seeing a positive or a negative stimulus in their left or right hemifield. Flexion responses were faster for positive stimuli, while negative stimuli were associated with faster extensions responses. Overall, performance was fastest when emotional stimuli were presented to the left visual hemifield. This right hemisphere superiority was especially clear for negative stimuli, while reaction times toward positive pictures showed no hemispheric difference. We did not find any interaction between hemifield and response type. Neither was there a triple interaction between valence, hemifield and response type. We suppose that response dichotomies in humans are not as tightly linked to a hemisphere- and valence-bound reaction type as previously assumed.     

Conditioned suppression in goldfish as a function of shock-reinforcement schedule

The conditioned suppression technique (Estes and Skinner, 1941) was employed to study the effects of partial-shock reinforcement in the goldfish. Lever-pressing behavior of hungry goldfish was suppressed in the presence of a flashing light that had been previously paired with electric shocks. Fish that acquired the suppression under 50% and 100% shock-reinforcement, respectively, were subjected to repeated presentations of the flashing light alone. This procedure revealed a more rapid extinction of the suppressed behavior in the 50% than in the 100% shocked group. The finding was compared with those from other experiments and possible reasons for the differences were examined.     

Eyeblink Conditioning in Rats Using Pontine Stimulation as a Conditioned Stimulus

Previous studies using rabbits and ferrets found that electrical stimulation of the pontine nuclei or middle cerebellar peduncle could serve as a conditioned stimulus (CS) in eyeblink conditioning (Bao, Chen, & Thompson, 2000; Hesslow, Svensson, & Ivarsson, 1999; Steinmetz, 1990; Steinmetz, Lavond, & Thompson, 1985; 1989; Steinmetz et al., 1986; Tracy, Thompson, Krupa, & Thompson, 1998). The current study used electrical stimulation of the pontine nuclei as a CS to establish eyeblink conditioning in rats. The goals of this study were to develop a method for directly activating the CS pathway in rodents and to compare the neural circuitry underlying eyeblink conditioning in different mammalian species. Rats were given electrical stimulation through a bipolar electrode implanted in the pontine nuclei paired with a periorbital shock unconditioned stimulus (US). Paired training was followed by extinction training. A subset of rats was given a test session of paired training after receiving an infusion of muscimol into the anterior interpositus nucleus. Rats given paired presentations of the stimulation CS and US developed CRs rapidly and showed extinction. Muscimol infusion prior to the test session resulted in a reversible loss of the eyeblink CR. The results demonstrate that electrical stimulation of the pontine nuclei can be used as a CS in rodents and that the CS pathway is similar in rats, rabbits, and ferrets. In addition, the loss of CRs following muscimol inactivation shows that the conditioning produced with pontine stimulation depends on cerebellar mechanisms.     

Conditioned suppression to odorous stimuli in pigeons,

The conditioned suppression technique was employed to establish criterion discrimination of an amyl acetate concentration of 3% of vapor saturation, and to generate differential response rates in the presence of equal concentrations of amyl acetate and butyl acetate. The magnitude of suppression was also recorded as a function of amyl acetate concentration, with the concentrations presented in descending, ascending, and irregular series. The three stimulus presentation procedures generated approximately equivalent suppression versus concentration functions. Amyl acetate suppression thresholds were 0.16%, 0.50%, and 0.73% of vapor saturation for three subjects. Amyl acetate, butyl acetate, and butyric acid thresholds for two additional subjects were approximately 0.10% of vapor saturation. No suppression was recorded during control trials.     

Conditioned taste aversion in humans using motion-induced sickness as the US

The purpose of the experiment was to demonstrate conditioned taste aversion (CTA) and latent inhibition (LI) of CTA in humans using rotation-induced motion sickness as the unconditioned stimulus. To accomplish this, flavour familiarity (familiar vs unfamiliar) and rotation (rotation vs no rotation) were manipulated in a 2 X 2 factorial design. Subjects consumed either a familiarly flavoured carbonated beverage or a novel one after which half of each group was rotated or not rotated. Two hours later the subjects were re-presented with the flavoured drink that they had previously drunk. The groups receiving rotation consumed less of the drink that the non-rotated groups, thus demonstrating CTA. The rotated group pre-exposed to the novel flavoured drink consumed less than the rotated group pre-exposed to the familiar drink, thus demonstrating LI. The effectiveness of the rotation procedure in producing motion sickness was confirmed by self-reports of general feelings and by symptom rating scales. In addition, it was found that, at the time of consuming the test drink the rotation groups' motion-sickness symptom scores were reduced to the level of the nonrotated groups. Applications of these data to the prophylactic treatment of chemotherapy-induced food aversions were discussed.     

Androstadienone in motor reactions of men and women toward angry faces

The endogenous compound androstadienone modulating the evaluation of others and activating the human fear system was hypothesized in terms of processing socially relevant cues by regulating responses to angry faces. Androstadienone was investigated in association with arm movements of 62 participants (30 women) in response to happy and angry facial expressions. Volunteers pushed away or pulled toward them a joystick as fast as possible on seeing either an angry or a happy cartoon face on a computer screen. This task was repeated twice: once during exposure to androstadienone masked with clove oil and once to clove oil only. In the former condition participants' reaction speed was accelerated, especially when reacting to angry faces. This observation may indicate an androstadienone-related activation of the fear system leading to faster responses to threat signals, assuming an enhanced allocation of attentional resources toward threat-related social cues.