Unpaired shocks during extinction weaken the contextual renewal of a conditioned discrimination

Renewal in human fear conditioning: A systematic review and meta-analysis

Renewal is a 'return of fear' manipulation in human fear conditioning to investigate learning processes underlying anxiety and trauma. Even though renewal paradigms are widely used, no study has compared the strength of different renewal paradigms. We conduct a systematic review (N = 80) and meta-analysis (N = 23) of human fear conditioning studies assessing renewal. Our analysis shows that the classic ABA design is the most effective paradigm, compared to ABC and ABBA designs. We present evidence that conducting extinction in multiple contexts and increasing the similarity between acquisition and extinction contexts reduce renewal. Furthermore, we show that additional cues can be used as safety and 'protection from extinction' cues. The review shows that alcohol weakens the extinction process and that older adults appear less sensitive to context changes and thus show less renewal. The large variability in approaches to study renewal in humans suggests that standardisation of fear conditioning procedures across laboratories would be of great benefit to the field.

The effects of extinction and an explicitly unpaired treatment on the reinforcing properties of a Pavlovian conditioned stimulus

This series of experiments examined the effects of extinction and an explicitly unpaired treatment on the ability of a conditioned stimulus (CS) to function as a reinforcer. Rats were trained to lever press for food, exposed to pairings of a noise CS and food, and, finally, tested for their willingness to lever press for the CS in the absence of the food. Experiment 1 provided a demonstration of conditioned reinforcement (using controls that were only exposed to unpaired presentations of the CS and food) and showed that it was equivalent after one or four sessions of CS-food pairings. Experiments 2 and 3 showed that, after one session of CS-food pairings, repeated presentations of the CS alone reduced its reinforcing properties; but after four sessions of CS-food pairings, repeated presentations of the CS alone had no effect on these properties. Experiment 4 showed that, after four sessions of CS-food pairings, explicitly unpaired presentations of the CS and food completely undermined conditioned reinforcement. Finally, Experiment 5 provided within-experiment evidence that, after four sessions of CS-food pairings, the reinforcing properties of the CS were disrupted by explicitly unpaired presentations of the CS and food but spared by repeated presentations of the CS alone. Together, these findings indicate that the effectiveness of extinction in undermining the reinforcing properties of a CS depends on its level of conditioning; and that, where extinction fails to disrupt these properties, they are successfully undermined by an explicitly unpaired treatment. They are discussed with respect to findings in the literature on Pavlovian-to-instrumental transfer; and the Rescorla-Wagner model, which anticipates that an explicitly unpaired treatment will be more effective than extinction in reversing the effects of conditioning.

The learning of prospective and retrospective cognitive maps within neural circuits

Brain circuits are thought to form a "cognitive map" to process and store statistical relationships in the environment. A cognitive map is commonly defined as a mental representation that describes environmental states (i.e., variables or events) and the relationship between these states. This process is commonly conceptualized as a prospective process, as it is based on the relationships between states in chronological order (e.g., does reward follow a given state?). In this perspective, we expand this concept on the basis of recent findings to postulate that in addition to a prospective map, the brain forms and uses a retrospective cognitive map (e.g., does a given state precede reward?). In doing so, we demonstrate that many neural signals and behaviors (e.g., habits) that seem inflexible and non-cognitive can result from retrospective cognitive maps. Together, we present a significant conceptual reframing of the neurobiological study of associative learning, memory, and decision making.

Presentation of unpaired unconditional stimuli during extinction reduces renewal of conditional fear and slows re-acquisition

Past research has shown that presenting unconditional stimuli (US) during extinction training, either paired with the conditional stimulus (CS) or explicitly unpaired, can reduce spontaneous recovery and slow the re-acquisition of conditional fear. Whether contextual renewal of conditioned fear as indexed by electrodermal responses and self-report measures of anxiety and CS evaluations is also reduced after presentation of paired or unpaired USs during extinction training is currently unclear. Three groups of participants (Paired, Unpaired, Standard Extinction) completed a sequence of habituation, acquisition, extinction, renewal, and re-acquisition phases. During extinction, five CS-US pairings were presented in group Paired, whereas five US were presented alone in group Unpaired. No US were presented during standard extinction. For all groups, extinction was conducted in a context that was different from that of the other phases. Extinction of differential electrodermal responding was evident in groups Unpaired and Standard, but not in group Paired. Contextual renewal and fast re-acquisition, as indexed by differential electrodermal responding, were evident in group Standard, but not in group Unpaired and differential electrodermal responding persisted in group Paired. After extinction, self-reported anxiety was higher in groups Paired and Unpaired, but differential CS evaluations were evident in group Paired only. The current results suggest that presenting additional unpaired USs during extinction training strengthens extinction and protects against the renewal of differential electrodermal responding.

Beyond Extinction: Prolonged Conditioning and Repeated Threat Exposure Abolish Contextual Renewal of Fear-Potentiated Startle Discrimination but Leave Expectancy Ratings Intact

Extinction treatments decrease fear via repeated exposures to the conditioned stimulus (CS) and are associated with a return of fear. Alternatively, fear can be reduced via reductions in the perceived intensity of the unconditioned stimulus (US), e.g., through repeated exposures to the US. Promisingly, the few available studies show that repeated US exposures outperform standard extinction. US exposure treatments can decrease fear via two routes: (1) by weakening the CS-US association (extinction-like mechanism), and/or (2) by weakening the subjective US aversiveness (habituation-like mechanism). The current study further investigated the conditions under which US exposure treatment may reduce renewal, by adding a group in which CS-US pairings continued following fear acquisition. During acquisition, participants learned that one of two visual stimuli (CS+/CS-) predicted the occurrence of an aversive electrocutaneous stimulus (US). Next, the background context changed and participants received one of three interventions: repeated CS exposures, (2) repeated US exposures, or (3) continued CS-US pairings. Following repeated CS exposures, test presentations of the CSs in the original conditioning context revealed intact CS+/CS- differentiation in the fear-potentiated startle reflex, while the differentiation was abolished in the other two groups. Differential US expectancy ratings, on the other hand, were intact in all groups. Skin conductance data were inconclusive because standard context renewal following CS exposures did not occur. Unexpectedly, there was no evidence for a habituation-like process having taken place during US exposures or continued CS-US pairings. The results provide further evidence that US exposures outperform the standard extinction treatment and show that effects are similar when US exposures are part of CS-US pairings.

Effects of occasional reinforced trials during extinction on the reacquisition of conditioned responses to food cues

BACKGROUND AND OBJECTIVES

Successful long-term dieting appears to be difficult, and part of its difficulty might be explained by processes related to classical appetitive conditioning. Increasing the speed of extinction of appetitive responses to food cues and decreasing the magnitude of returns of these responses could help increase the long-term effectiveness of weight loss attempts. Two extinction techniques hypothesized to slow down rapid reacquisition of conditioned appetitive responses were investigated: the provision of 1) occasional reinforced extinction trials (OR) and 2) unpaired unconditioned stimuli (USs) during extinction (UNP).

METHODS

After acquisition, participants (N = 90) received one of three extinction trainings: OR, UNP, or normal extinction (control), followed by a reacquisition phase. Their desire to eat, US expectancy, and salivation were measured. Effects of impulsivity on different phases of appetitive conditioning were also assessed.

RESULTS

It was found that both extinction techniques were successful in reducing the rate of reacquisition of US expectancies. Participants in the OR condition also demonstrated a slower extinction of US expectancies and desires to eat. However, the reacquisition of conditioned desires was not affected by either extinction technique. Impulsivity did not moderate responses during acquisition or extinction, but appeared to slow down the reacquisition of conditioned desires.

LIMITATIONS

US expectancies and eating desires were not completely extinguished, and a few differences in baseline responses caused difficulty in interpreting some of the findings.

CONCLUSIONS

It is concluded that the provision of occasional reinforced extinction trials and unpaired USs seem promising techniques to slow down reacquisition, but that additional studies are needed.

Attribute conditioning: Changing attribute-assessments through mere pairings

We propose Attribute Conditioning (AC) as a form of learning that refers to changes in people's assessment of stimuli's (CSs) attributes due to repeated pairing with stimuli possessing these attributes (USs). We review the available evidence and, based on this review, delineate three open questions and investigate them experimentally: a) the moderating role of CS-US similarity; b) the possibility of blocking; and c) the possibility of extinction. Five experiments conditioned health and athleticism. We measured AC effects on direct and indirect dependent variables (direct ratings and semantic misattribution). Experiment 1 shows that CS-US feature similarity does not moderate AC. Experiments 2 and 3 show that AC effects are insensitive to blocking; and Experiments 4 and 5 show that AC effects are resistant to extinction. These five experiments show that AC depends on CS-US contiguity, but not on CS-US contingency. Thereby, the study establishes AC as a simple learning phenomenon describing how people, stimuli, and concepts acquire specific attributes in people's minds due to mere pairings.

Unpaired extinction: implications for treating post-traumatic stress disorder

Extinction of fear is important for treating stress-related conditions particularly post-traumatic stress disorder (PTSD). Although traditional extinction presents the feared stimulus by itself, there is evidence from both clinical and basic research that repeatedly presenting the feared stimulus by itself does not prevent fear from returning. This renewal or relapse can be "thwarted" by unpaired extinction-presentations of the feared stimulus and the event producing the fear. However, no matter how effective standard unpaired extinction may be in the laboratory, repeated presentation of a traumatic event is untenable. To make an unpaired extinction procedure more clinically relevant, we classically conditioned the rabbit nictitating membrane response using electrical stimulation or air puff as the unconditioned stimulus and then during unpaired extinction reduced both the intensity of the unconditioned stimulus and the days of unpaired stimulus presentations. We found unpaired extinction reduced conditioned and exaggerated unconditioned responding (an animal analog of PTSD called conditioning-specific reflex modification) and could be accomplished with a weak unconditioned stimulus as long as extended presentations were used. Surprisingly, brief presentations of a weak unconditioned stimulus or extended presentations of a strong one made the exaggerated responses stronger. One implication is that brief treatment may not just be ineffectual; it may heighten the symptoms of PTSD. Another implication is that using strong stimuli may also heighten those symptoms.

A comparison of explicitly unpaired treatment and extinction: recovery of sign-tracking within a context renewal design

The present experiment compared the effectiveness of explicitly unpaired treatment and extinction in preventing the recovery of sign-tracking within a context renewal design. Three groups of rats were first trained on a sign-tracking procedure in Context A where insertions of a retractable lever were paired with food. In a second phase, the sign-tracking response was eliminated. One group received standard extinction of the CS in Context B, while another group received explicitly unpaired treatment in Context B where food was presented only during inter-trial intervals (and not paired with the lever). A third group received this explicitly unpaired treatment in Context A. After the sign-tracking response was eliminated, all groups received a test session in Context A where the lever was presented alone and no food was delivered at any time. Significantly more responding occurred in the group that received explicitly unpaired treatment in Context B than in either of the other groups. This demonstrates that there are situations where explicitly unpaired treatment is less effective than extinction in preventing the reappearance of previously eliminated responding.