Lipopolysaccharide (LPS) attenuates the primary conditioning of lithium chloride (LiCl)-induced context aversion but not the secondary conditioning of context aversion or taste avoidance

A first-order association can be formed between toxin-induced nausea and a context, as well as nausea and a taste cue. However, comparatively little is understood about second-order associations. The present study examined if the bacterial endotoxin, LPS, could impair the first- and second-order conditioning of context aversion (anticipatory nausea paradigm) and subsequent conditioned taste avoidance (two-bottle task). Adult male Long Evans rats were treated with LiCl (127 mg/kg, intraperitoneal [i.p.]) or vehicle control (NaCl) and then exposed to a distinct context for 4 first-order conditioning trials. LPS (200 μg/kg, i.p.) or NaCl were administered 24 h after each trial. Seventy-two h after the final first-order conditioning trial, rats underwent 2 second-order conditioning trials where they were treated with 2% saccharin (i.p.) and then exposed to the same context. Twenty-four h after the final second-order conditioning trial, rats were tested in a two-bottle task (2 trials), where they were given a choice between water and a palatable 0.2% saccharin solution. LiCl-treated rats demonstrated a context aversion by the 3rd conditioning trial in the anticipatory nausea paradigm. Rats previously exposed to LiCl also displayed a conditioned taste avoidance of saccharin within the two-bottle task. LPS attenuated first-order context aversion but did not alter either second-order context aversion or conditioned taste avoidance in the two-bottle task. This study demonstrated that a secondary association formed within an aversive context could result in a conditioned taste avoidance. Further, LPS may be able to attenuate primary conditioning, but not secondary conditioning.

Enhanced conditioned "liking" of novel visual cues paired with alcohol or non-alcohol beverage container images among individuals at higher risk for alcohol use disorder

RATIONALE/OBJECTIVE

This study used an evaluative conditioning (EC) procedure to assess the affective properties of a CS for ingested drug reward in humans. Specifically, the study tested whether the evaluative response ("liking"/"disliking") to an arbitrary visual stimulus ("CS₂," e.g., a purple hexagon) could be changed through pairings with an alcohol or non-alcohol beverage cue ("CS₁," e.g., a full wine glass, a juice box), which is ostensibly a conditioned visual predictive stimulus for alcohol or non-alcohol liquid reward, respectively.

METHODS

Participants (N = 369, 18-23 years, 66% female, 79% white, 21% reporting no alcohol use ever or in the past year) received 24 CS₁ pairings with each CS₂. CS₂ and CS₁ evaluations were assessed pre- and post-conditioning.

RESULTS

Alcohol and non-alcohol CS₂ "liking" correlated with alcohol use. "Liking" of the alcohol but not non-alcohol CS₁ also correlated with alcohol use. Alcohol CS₁ "liking" also correlated with alcohol and non-alcohol CS₂ 'liking," whereas non-alcohol CS₁ 'liking" correlated with non-alcohol but not alcohol CS₂ "liking."

CONCLUSIONS

Taken together, findings support the idea that drug-related visual stimuli acquire appetitive (hedonic and/or incentive) properties as a function of individual differences in drug use, which entail individual differences in exposure to the conditioning effects of addictive substances like alcohol. Findings also suggest a link between drug use and the propensity to attribute affective/motivational significance to reward-predictive cues in general.

Avoiding a feared stimulus: Modelling costly avoidance of learnt fear in a sensory preconditioning paradigm

Avoidance of learnt fear prevents the onset of a feared stimulus and the threat that follows. In anxiety-related disorders, it turns pathological given its cost and persistence in the absence of realistic threat. The current study examined the acquisition of costly avoidance of learnt fear in healthy individuals (n = 45), via a sensory preconditioning paradigm. Two neutral preconditioning stimuli (PSs) were paired with two neutral conditioned stimuli (CSs). One CS then came to predict an aversive outcome whereas the other CS came to predict safety. In test, participants engaged in stronger avoidance to the PS associated with the fear-related CS than the PS associated with the safety-related CS. Of note, executing behavioral avoidance led to missing out a competing reward, thus rendering avoidance costly. The results also provide preliminary evidence that threat anticipation and a negative change in valence play a role in driving costly avoidance of learnt fear. Future studies should examine how avoidance of learnt fear maintains pathological anxiety.

Trait anxiety is associated with reduced typicality asymmetry in fear generalization

In fear conditioning, training with typical category exemplars has been shown to promote fear generalization to novel exemplars of the same category, whereas training with atypical category exemplars supports limited if any generalization to other category members, amounting to a typicality asymmetry in fear generalization. The present study sought to examine how trait anxiety bears on typicality asymmetry in fear generalization. Participants in one condition were presented with typical exemplars during fear acquisition and atypical exemplars of the same category in the subsequent generalization test (typical condition), whereas in the other group, atypical and typical exemplars were presented during fear acquisition and generalization test, respectively (atypical condition). We observed a typicality asymmetry in fear generalization in self-reported expectancy ratings in low trait anxious individuals only. High trait anxious individuals showed a similar degree of fear generalization in both conditions. The current results help illuminate why some individuals are at risk for exhibiting broad fear generalization after exposure to an aversive event.

Higher-order conditioning of taste-odor learning in rats: Evidence for the association between emotional aspects of gustatory information and olfactory information

Previous studies have shown that rats prefer an odor paired with saccharin solution to an odor paired with quinine solution (taste-odor learning). However, it remains unclear whether the odors are associated with the emotional (i.e., positive and/or negative hedonics) or qualitative (i.e., sweetness and/or bitterness) aspects of gustatory information. This study aimed to examine this question using higher-order conditioning paradigms: second-order conditioning (SOC) and sensory preconditioning (SPC). Adult Wistar rats were divided into SOC and SPC groups. Food flavors, purchased from a Japanese market, such as melon (0.05%), lemon (0.1%), vanilla (0.1%), and almond (0.1%), were randomly used as odors A, B, C, and D for each rat. The SOC group was exposed to 0.005M saccharin solutions with odor A and 0.02M quinine solutions with odor C in the first 5days of learning. Additionally, they were exposed to water with a mixture of odors A and B, and water with a mixture of odors C and D in the next 5days of learning. The order of these two learning sessions was reversed in the SPC group. We hypothesized that if odor was associated with the emotional, or qualitative, aspects of gustatory information, the SOC, or SPC groups, respectively, would prefer odor B to odor D. Our results showed that the SOC group preferred odor B to odor D, whereas the SPC group did not show any such preference. This suggests that odors may be primarily associated with emotion evoked by gustation in taste-odor learning.

Conditioned cortical reactivity to cues predicting cigarette-related or pleasant images

Through Pavlovian conditioning, reward-associated neutral stimuli can acquire incentive salience and motivate complex behaviors. In smokers, cigarette-associated cues may induce cravings and trigger smoking. Understanding the brain mechanisms underlying conditioned responses to cigarette-associated relative to other inherently pleasant stimuli might contribute to the development of more effective smoking cessation treatments that emphasize the rehabilitation of reward circuitry. Here we measured brain responses to geometric patterns (the conditioned stimuli, CSs) predicting cigarette-related, intrinsically pleasant and neutral images (the unconditioned stimuli, USs) using event-related potentials (ERPs) in 29 never-smokers, 20 nicotine-deprived smokers, and 19 non-deprived smokers. Results showed that during US presentation, cigarette-related and pleasant images prompted higher cortical positivity than neutral images over centro-parietal sensors between 400 and 800ms post-US onset (late positive potential, LPP). The LPP evoked by pleasant images was significantly larger than the LPP evoked by cigarette images. During CS presentation, ERPs evoked by geometric patterns predicting pleasant and cigarette-related images had significantly larger amplitude than ERPs evoked by CSs predicting neutral images. These effects were maximal over right parietal sites between 220 and 240ms post-CS onset and over occipital and frontal sites between 308 and 344ms post-CS onset. Smoking status did not modulate these effects. Our results show that stimuli with no intrinsic reward value (e.g., geometric patterns) may acquire rewarding properties through repeated pairings with established reward cues (i.e., cigarette-related, intrinsically pleasant).

Is the Source of Reinforcement for Naming Multiple Conditioned Reinforcers for Observing Responses?

Naming refers to the incidental acquisition of word-object relations as listener and speaker without explicit reinforcement. To investigate possible sources of reinforcement for naming, we examined the effects of a procedure for conditioning reinforcement for observing responses on the emergence of naming in children who previously lacked it. The participants were three 5- to 7-year-old children with and without diagnoses of autism spectrum disorder. During the intervention, either visual or auditory stimuli were first conditioned as reinforcers for observing responses. Then, neutral visual or auditory stimuli were paired with the conditioned visual or auditory stimuli until both visual and auditory stimuli acquired reinforcing properties for observing. Following this intervention, the participants demonstrated naming of stimuli that had been used in pretests for naming, as well as on a novel set of stimuli. We observed increases in echoic responding in conjunction with the emergence of naming and conditioned reinforcement for both observing responses. We interpret the data as suggesting that listener and speaker repertoires are joined for naming only when both visual and auditory stimuli reinforce the observing responses of looking and listening simultaneously.