Expectation violation has been shown to engage adaptive memory formation, resulting in better memory for unexpected information. In two experiments we tested whether this mechanism is engaged dynamically in a goal-irrelevant manner during retrieval, and how it affects trial-by-trial recognition. Participants encoded images of objects, and then learned a contingency between a cue and category (man-made or natural) with new objects. Targets and parametrically manipulated similar foils, comprising set events, were used at retrieval. In each retrieval trial a cue appeared, which either matched or mismatched (according to the established contingency) the following object, for which participants made an old/new decision. We found that unexpected events at retrieval were associated with increased activation along the ventral visual stream, whereas expected events engaged parietal regions of the core recollection network. For targets and most similar foils, we found an interaction between current and previous expectation status on memory performance, such that expected events following unexpected ones (UprevEcurr) showed a boost in performance. This behavioural effect was associated with activation in the hippocampus, SN/VTA and occipital cortex. A combination of two unexpected events (UprevUcurr) resulted in the poorest memory performance and was associated with increased activation in occipital cortex. Taken together, our findings suggest expectation violation engages an encoding mechanism, supported by bottom-up processing, in a task-independent manner. Therefore, when the goal is to retrieve information, the mnemonic consequences of the shift towards an encoding state is detrimental in real-time, but beneficial for subsequent similar events.
bioRxiv Subject Collection: Neuroscience