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Summary: Attention or variations in event processing help drive learning. Lesion studies have implicated the central nucleus of the amygdala (CeA) in this process, particularly when expected rewards are omitted. However, lesion studies cannot specify how information processing in CeA supports such learning. To address these questions, we recorded CeA neurons in rats performing a task in which rewards were delivered or omitted unexpectedly. We found that activity in CeA neurons increased selectively at the time of omission and declined again with learning. Increased firing correlated with CeA-inactivation sensitive measures of attention. Notably CeA neurons did not fire to the cues or in response to unexpected rewards. These results indicate that CeA contributes to learning in response to reward omission due to a specific role in signaling actual omission rather than a more general involvement in signaling expectancies, errors, or reward value. [ABSTRACT FROM AUTHOR]

The discovery that dopamine neurons signal errors in reward prediction has demonstrated that concepts empirically derived from the study of animal behavior can be used to understand the neural implementation of reward learning. Yet the learning theory models linked to phasic dopamine activity treat attention to events such as cues and rewards as static quantities; other models, such as Pearce-Hall, propose that learning might be influenced by variations in processing of these events. A key feature of these accounts is that event processing is modulated by unsigned rather than signed reward prediction errors. Here we tested whether neural activity in rat basolateral amygdala conforms to this pattern by recording single units in a behavioral task in which rewards were unexpectedly delivered or omitted. We report that neural activity at the time of reward is providing an unsigned error signal with characteristics consistent with those postulated by these models. This neural signal increased immediately after a change in reward, and stronger firing was evident whether the value of the reward increased or decreased. Further, as predicted by these models, the change in firing developed over several trials as expectations for reward were repeatedly violated. This neural signal was correlated with faster orienting to predictive cues after changes in reward, and abolition of the signal by inactivation of basolateral amygdala disrupted this change in orienting and retarded learning in response to changes in reward. These results suggest that basolateral amygdala serves a critical function in attention for learning. [ABSTRACT FROM AUTHOR]

Aversive states are proposed to drive addiction. Here, Wheeler and colleagues show that drug-associated cues come to activate neural representations of aversive information in nucleus accumbens and that this activation predicts subsequent drug use. These remarkable data identify a potential neural substrate through which aversive affective representations may motivate drug use. [Copyright &y& Elsevier]

Addicts and drug-experienced animals have decision-making deficits in reversal-learning tasks and more complex 'gambling' variants. Here we show evidence that these deficits are mediated by persistent encoding of outdated associative information in the basolateral amygdala. Cue-selective neurons in the basolateral amygdala, recorded in cocaine-treated rats, failed to change cue preference during reversal learning. Further, the presence of these neurons was critical to the expression of the reversal-learning deficit in the cocaine-treated rats. [ABSTRACT FROM AUTHOR]