The Processing of Immediate and Delayed Feedback – A Critical Role of the Learned Type of Association?

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Learning from feedback enables us to adapt to the environment. Recent evidence has shown that the neural mechanisms of feedback processing depend on the delay between the feedback-predicting event and the feedback itself. While for immediate feedback the striatum is important, feedback that is delayed by a few seconds recruits the hippocampus. To date, however, the differences in the cognitive and neural mechanisms between learning from immediate and delayed feedback have not clearly been elucidated. The main assumption we want to test in this project is that feedback delay effects on feedback processing can be explained by different mechanisms of credit assignment for immediate and delayed feedback. Credit assignment refers to the question, how an association between an event and feedback can be established, if, for example, other events intervene. Recently, a learning mechanism based on temporal proximity has been identified. This learning mechanism is mediated by a motor circuit between striatum and cortex, suggesting that it refers more to the integration of actions with feedback than to stimulus-feedback associations. Accordingly, we hypothesize that the FRN, an event-related potential (ERP) component linked to the striatum and anterior cingulate cortex, is more pronounced for action-feedback than stimulus-feedback associations, but only for immediate feedback. For delayed feedback, in turn, we assume that a different mechanism of credit assignment prevails, namely the feedback-locked reactivation of brain regions representing the processing of the associated event. Feedback-locked brain activity should thus differ between action-feedback and stimulus-feedback associations. Accordingly, we hypothesize that the N170, an ERP component generated in extrastriate visual areas, is more pronounced for (visual) stimulus-feedback than action-feedback associations, but only for delayed feedback. Finally, functional neuroimaging will be used to further support the assumption that feedback-locked reactivation plays an important role for delayed feedback processing. Specifically, we hypothesize that associations between different categories of visual stimuli and feedback lead to distinguishable patterns of feedback-locked brain activity, mediated by the hippocampus, only for delayed but not immediate feedback. Machine-learning techniques (multivoxel pattern analysis) will be used to predict the category of the associated stimulus (faces or scenes) from feedback-locked brain activity.