This article provides a selective review and integration of the behavioral literature on Pavlovian extinction. The first part reviews evidence that extinction does not destroy the original learning, but instead generates new learning that is especially context-dependent. The second part examines insights provided by research on several related behavioral phenomena (the interference paradigms, conditioned inhibition, and inhibition despite reinforcement). The final part examines four potential causes of extinction: the discrimination of a new reinforcement rate, generalization decrement, response inhibition, and violation of a reinforcer expectation. The data are consistent with behavioral models that emphasize the role of generalization decrement and expectation violation, but would be more so if those models were expanded to better accommodate the finding that extinction involves a context-modulated form of inhibitory learning.

/pdf/context-and-behavioral-processes-in-extinction-1xm3d3evmg.pdf

Context and Behavioral Processes in Extinction.

Context, ambiguity, and unlearning: sources of relapse after behavioral extinction.

The objective of this article is to review data from studies that used a reinstatement model in rats to elucidate the neural mechanisms underlying relapse to heroin and cocaine seeking induced by exposure to the self-administered drug (drug priming), conditioned drug cues, and stressors. These factors were reported to contribute to relapse to drug use in humans following prolonged abstinence periods. In the reinstatement model, the ability of acute exposure to drug or nondrug stimuli to reinstate drug seeking is determined following training for drug self-administration and subsequent extinction of the drug-reinforced behavior. We will review studies in which pharmacological agents were injected systemically or intracranially to block (or mimic) reinstatement by drug priming, drug cues, and stressors. We also will review studies in which brain lesions, in vivo microdialysis and electrochemistry, and gene expression methods were used to map brain sites involved in relapse to drug seeking. Subsequently, we will discuss theoretical issues related to the processes underlying relapse to drugs and address methodological issues in studies on reinstatement of drug seeking. Finally, the implications of the findings from the studies reviewed for addiction theories and treatment will be discussed. The main conclusion of this review is that the neuronal mechanisms involved in relapse to heroin and cocaine seeking induced by drug priming, drug cues, and stressors are to a large degree dissociable. The data reviewed also suggest that the neuronal events mediating drug-induced reinstatement are to some degree dissociable from those mediating drug reinforcement.

Neurobiology of Relapse to Heroin and Cocaine Seeking: A Review

The role of the dorsomedial prefrontal cortex, basolateral amygdala, and dorsal hippocampus in contextual reinstatement of cocaine seeking in rats.

Theories of associative learning are concerned with the factors that govern association formation when two stimuli are presented together. In this article we review the relative merits of the currently influential theories of associative learning. Some theories focus on the role of attention in association formation, but differ in the rules they propose for determining whether or not attention is paid to a stimulus. Other theories focus on the nature of the association that is formed, but differ as to whether this association is regarded as elemental, configural, or hierarchical. Recent developments involve modifications to existing theories in order to account for associative learning between two stimuli, A and B, when A is accompanied, not by B, but by a stimulus that has been paired with B. The implications of the theories for understanding how humans derive causal judgments and solve categorization problems is considered.

http://psych.mcmaster.ca/hannahsd/pearcebouton'01.pdf

Theories of Associative Learning in Animals

Renewal of Extinguished Lever-Press Responses upon Return to the Training Context

We explored renewal of formerly acquired and then extinguished fear in rats. After 24 paired trials of a tone and an electric shock, acquired fear to the tone was extinguished in another context by repeated exposure to the tone alone. Conditioned fear was behaviorally extinguished by the 32nd trial of tone exposure; 40 or 80 additional extinction trials (i.e., a total of 72 or 112 extinction trials) were administered to independent groups of rats. Extinguished fear was renewed by testing the tone in the original context, independently of the amount of the preceding extinction training. The finding suggests that this type of fear renewal is difficult to prevent even after extensive extinction training prior to context change. Fear renewal also took place by shifting contexts after 72 extinction trials, when the fear had been extinguished in the context of acquisition. This kind of renewal was, however, prevented by extending extinction training to 112 trials.

/pdf/renewal-of-formerly-conditioned-fear-in-rats-after-extensive-43e02q7p6i.pdf

Sadahiko Nakajima

Papers

Renewal of Extinguished Lever-Press Responses upon Return to the Training Context

Renewal of Formerly Conditioned Fear in Rats after Extensive Extinction Training

Renewal of operant performance formerly eliminated by omission or noncontingency training upon return to the acquisition context

Taste aversion in rats induced by forced swimming, voluntary running, forced running, and lithium chloride injection treatments

Taste aversion induced by confinement in a running wheel