![]() Second, the hippocampus may have been involved because the associations had been learned very recently, and this role would diminish over time with the neocortex playing a more autonomous role as a result of systems consolidation 8– 10 (cf. First, it could be explained in terms of the unique computational repertoire of the hippocampus, with processes like multimodal binding and pattern completion serving an important function in prediction regardless of the more canonical role of the hippocampus as a memory system 6, 7. This role for the hippocampus in action-based predictive coding can be interpreted in two ways. No reliable decoding effects were obtained in either the hippocampus or EVC for nonpredictive actions (i.e., actions that did not determine which outcome appeared after a cue). For predictive actions (i.e., actions that determine an outcome given a cue), multivariate pattern decoding revealed that the hippocampus represents the full cue-action-outcome sequence and that this is related within and across participants to evidence of the same outcome in early visual cortex (EVC), as measured with a separate classifier trained on outcome-only trials. However, on a subset of trials in the scanner, the outcome stimulus was omitted and replaced by a blank screen. The day after training, participants were scanned with fMRI while performing the same task with the pre-learned associations. Participants were trained behaviorally on cue-action-outcome sequences: in response to a visual cue, they chose between two manual actions that were either predictive or nonpredictive of the visual outcome that next appeared. These retrieved consequences could in turn get reinstated via feedback to sensory systems - a form of memory-based predictive coding of action outcomes.Ī recent study provided suggestive evidence for this mechanism, discovering a link between pattern completion in the hippocampus and predictive coding in visual cortex 3. ![]() These representations could contain information about the cue and action, but additionally the yet-to-occur sensory consequences of the action. Once these links are formed, making an action in response to a familiar cue may prompt the hippocampus to retrieve a conjunctive representation of past events. Repeated experience and interaction allows associative learning mechanisms in the hippocampus to bind recurring patterns of objects and actions over space and time 4, 5. ![]() A neural source of such predictions may be pattern completion in the hippocampus 1– 3. Hippocampal prediction may initially reflect indiscriminate binding of co-occurring of events, with action information pruning weaker associations and leading to more selective and accurate predictions over time.Īs you open the door to a familiar room, you are able to anticipate that specific objects that will come into view. However, three-day-old associations led to stronger background connectivity and greater differentiation between neural patterns for predictive vs. Just-learned associations led to comparable background connectivity between the hippocampus and V1/V2, regardless of whether actions predicted outcomes. How does this role for the hippocampus in action-based prediction change over time? We used high-resolution fMRI and a dual-training behavioral paradigm to examine how the hippocampus interacts with visual cortex during predictive and nonpredictive actions learned either three days earlier or immediately before the scan. These expectations can result from retrieval of action-outcome associations in the hippocampus and the reinstatement of anticipated outcomes in visual cortex. ![]() When an action is familiar, we are able to anticipate how it will change the state of the world. ![]()
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