Abstract
Extinction is a fundamental form of memory updating in which one learns to stop expecting an event that no longer occurs. This learning ensues when one experiences a change in environmental contingencies, that is, when an expected outcome fails to occur (simple extinction), or when a novel inflated expectation of a double outcome (overexpectation) is in conflict with the real outcome, and is a process that has been linked to amygdala function. Here, we show that in rats, the same neuronal population in the amygdala central nucleus updates reward expectancies and behaviour in both types of extinction, and neural changes in one paradigm are reflected in the other. This work may have implications for the management of addiction and anxiety disorders that require treatments based on the outcome omission, and disorders such as obesity that could use overexpectation, but not omission strategies.
Highlights
Extinction is a fundamental form of memory updating in which one learns to stop expecting an event that no longer occurs
Our findings show that omission and overexpectation are processed by an overlapping set of central nucleus (CN) cells, and this population predicts the decline in behavioural responding that is characteristic of extinction learning
The overexpectation condition was created by presenting two previously reinforced stimuli (A1V1: one auditory, one visual) in compound. This led to a prediction of additional reward; yet this compound was reinforced with the same two pellets delivered on trials during conditioning
Summary
Extinction is a fundamental form of memory updating in which one learns to stop expecting an event that no longer occurs. In an ever-changing world, the brain must constantly update its predictions, so that costly resources are no longer spent in attempts to acquire previously offered but unavailable rewards Such a reduction in the predictive potency of a cue can be achieved by holding the expectation constant and manipulating the delivery of the outcome—that is, simple extinction1—or by holding outcome delivery constant and manipulating the expectation—that is, overexpectation[2,3]. Understanding the representation of these different types of extinction in the brain poses novel questions about the neural and behavioural processes that govern the renewal or recovery from extinction learning[2,3,6] This may help the development of clinical treatments that effectively reduce the predictive power or acquired valence of cues such as exposure therapy or abstinence. Our findings show that omission and overexpectation are processed by an overlapping set of CN cells, and this population predicts the decline in behavioural responding that is characteristic of extinction learning
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