CS-UCS Contingency Research Articles

Pupil dilation tracks divergent learning processes in aware versus unaware Pavlovian conditioning.

Evidence regarding unaware differential fear conditioning in humans is mixed and even less is known about the effects of contingency awareness on appetitive conditioning. Phasic pupil dilation responses (PDR) might be more sensitive for capturing implicit learning than other measures, such as skin conductance responses (SCR). Here, we report data from two delay conditioning experiments utilizing PDR (alongside SCR and subjective assessments) to investigate the role of contingency awareness in aversive and appetitive conditioning. In both experiments, valence of unconditioned stimuli (UCS) was varied within participants by administering aversive (mild electric shocks) and appetitive UCSs (monetary rewards). Preceding visual stimuli (CSs) predicted either the reward, the shock (65% reinforcement), or neither UCS. In Exp. 1, participants were fully instructed about CS-UCS contingencies, whereas in Exp. 2, no such information was given. PDR and SCR demonstrated successful differential conditioning in Exp. 1 and in (learned) aware participants in Exp. 2. In non-instructed participants who remained fully unaware of contingencies (Exp. 2), differential modulation of early PDR (immediately after CS onset) by appetitive cues emerged. Associations with model-derived learning parameters further suggest that early PDR in unaware participants mainly reflect implicit learning of expected outcome value, whereas early PDR in aware (instructed/learned-aware) participants presumably index attentional processes (related to uncertainty/prediction error processing). Similar, but less clear results emerged for later PDR (preceding UCS onset). Our data argue in favor of a dual-process account of associative learning, suggesting that value-related processing can take place irrespective of mechanisms involved in conscious memory formation.

Fear-Conditioning Mechanisms Associated with Trait Vulnerability to Anxiety in Humans

SummaryInvestigations of fear conditioning in rodents and humans have illuminated the neural mechanisms underlying cued and contextual fear. A critical question is how personality dimensions such as trait anxiety act through these mechanisms to confer vulnerability to anxiety disorders, and whether humans' ability to overcome acquired fears depends on regulatory skills not characterized in animal models. In a neuroimaging study of fear conditioning in humans, we found evidence for two independent dimensions of neurocognitive function associated with trait vulnerability to anxiety. The first entailed increased amygdala responsivity to phasic fear cues. The second involved impoverished ventral prefrontal cortical (vPFC) recruitment to downregulate both cued and contextual fear prior to omission (extinction) of the aversive unconditioned stimulus. These two dimensions may contribute to symptomatology differences across anxiety disorders; the amygdala mechanism affecting the development of phobic fear and the frontal mechanism influencing the maintenance of both specific fears and generalized anxiety.

Cognitive training during infancy and adolescence accelerates adult associative learning: Critical impact of age, stimulus contingency and training intensity

A growing body of evidence supports the hypothesis that juvenile cognitive training shapes neural networks and behavior, and thereby determines the adult´s capacity for learning and memory. In particular, we have shown that infant rats, even though they do not develop an active avoidance strategy in a two-way active avoidance task, show as adults accelerated learning in the same learning task. This indicates that a memory trace was formed in the infant rats, which most likely is recruited during adult training. To identify the learning conditions, which are essential prerequisites to form this memory trace in infancy or adolescence, we investigated the critical impact of: (i) age, (ii) CS–UCS contingency, and (iii) pre-training intensity on this facilitating effect. We observed: (i) an age-dependent improvement of avoidance learning, (ii) that the beneficial impact of infant or adolescent pre-training on adult learning increases with the age at pre-training, (iii) that CS–UCS contingency during infant pre-training was most efficient to accelerate adult learning, (iv) that pre-training intensity (i.e. number of pre-training trials) was positively correlated with the pre-training induced acceleration of adult learning, and (v) that infant rats, compared to adolescent rats, need a higher training intensity to show learning improvement as adults. These results indicate that infant rats develop a goal-oriented escape strategy, which during adult training is replaced by an avoidance strategy, facilitated by the recruitment of the CS–UCS association, which has been learned during infant training. Based on these results the future challenge will be to identify the specific contribution of prefronto-limbic circuits in infant and adult learning in relation to their functional maturation.

Correlación entre la conciencia de la relación EC-EI y el efecto del condicionamiento de la evaluación

Some of the experimental evidence about the independence between awareness and evaluative conditioning arises from studies that employ correlational analysis. In this paper, we criticise some aspects of these studies and carry out an experiment in which we try to solve the problems they entail. Data show a positive and significant correlation between explicit knowledge about CS-UCS contingencies and conditioning effect size. The differences between this pattern of results and the one found in the former experiments are fitted into a model of evaluative conditio- ning. The model proposes two concurrent processes which operate as function of stimuli class and involve different levels of awareness.

The influence of CS-UCS perceptual similarity/dissimilarity on human evaluative learning and signal learning

In this study we examined the influence of CS-UCS perceptual similarity and dissimilarity relationships on human evaluative conditioning (i.e., changes in the intrinsic affective-evaluative value of CSs) and on human signal learning (i.e., the acquisition of knowledge about the CS-UCS contingency). On the basis of the scarce relevant findings in the literature (e.g., Levey & Martin, 1987, in Theoretical foundations of behavior therapy), it was hypothesized that CS-UCS perceptual similarity would enhance, whereas perceptual dissimilarity would impair or abolish, evaluative conditioning. As to the influence of (dis)similarity on signal learning, our strategy was basically exploratory. The perceptual (dis)similarity factor was manipulated on a within-subject basis, and a design was used allowing for straightforward conclusions concerning the role of perceptual (dis)similarity. No evidence was found for an influence of CS-UCS (dis)similarity on evaluative conditioning. On the other hand, CS-UCS similarity clearly facilitated signal learning, as indicated by a questionnaire asking for different aspects of learning about the CS-UCS contingency. Some remarkable parallels with recent animal conditioning findings are suggested.

UCS revaluation and conditioning models of acquired fears

Recent developments in the study of Pavlovian conditioning in humans have suggested that the strength of a conditioned response (CR) is affected not only by associative processes that link the conditioned stimulus (CS) with the unconditioned stimulus (UCS), but also by processes which lead the individual to revalue the UCS itself. These latter processes can frequently lead to dramatic changes in CR strength independently of any experience with the CS-UCS contingency. This paper discusses a number of ways in which UCS revaluation can be effected in human subjects, and discusses their implications for conditioning models of acquired fears.

Classical conditioning of skeletal avoidance responses in two strains of rats.

Anticipatory skeletal responses can be directly elicited during classical aversive conditioning in the shuttlebox. Under the classical CS-UCS contingency Long-Evans rats shuttle at moderate rates, while Fischer344 rats display high rates of anticipatory responding, even though the instrumental avoidance contingency is absent. The classical contingency is also exceedingly important in determining the differences between these strains, as well as their initial and terminal rates of anticipatory responding, when the avoidance contingency is present.

Differential eyelid conditioning to stimuli that express a response-related command or convey reinforcement-related information

Either command words, BLINK and DON'T BLINK, or informing words, PUFF and NO PUFF, were used as differential conditioned stimuli with a corneal airpuff UCS. For half the Ss the stimuli expressed commands that were compatible with the appropriate CR or gave information which was congruent with the CS-UCS contingency, and for half the Ss the command was incompatible or the information incongruent. Effects of incompatibility and incongruity depended upon the topography of the S's eyelid CR! For Ss giving the gradual C form the CS-UCS reinforcement contingencies overcame effects of incompatible command or incongruent information, but for Ss giving the rapid, complete V form incompatibility or incongruity seriously disrupted the discrimination, suggesting that Vs have more difficulty than Cs in recording verbal information.

Recall as a Function of Awareness of CS-UCS Contingency

Ss were presented with a list of words some of which were followed by shock, others not followed by shock. Ss were aware of the relationship between shock and some of the shocked words (SA words) but were unaware of this relationship for others of the shocked words (SU words). One-half of the Ss recalled the words immediately, the other half after a 30-min. delay. Delayed recall of SU words was inferior to that of SA words and delayed recall of SU words was inferior to that of immediate recall of SU words. The results indicated that shock resulted in a decrease in delayed recall when S was unaware of the CS-UCS contingency.