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Abstract:
Concepts represent combinations of features shared by similar entities and allow generalization from limited experience to novel situations. It has been proposed that the hippocampal-entorhinal system contributes to concept learning by representing the relations between experiences along relevant feature dimensions. However, how the system provides access to abstracted information remains unclear. In the present fMRI study, we investigated whether this map-like representation of concepts supports the retrieval of category prototypes to guide behavior in a feature inference task. After participants were trained to categorize a set of exemplars based on the combination of two of their features, they were presented with partial stimuli and had to infer the missing feature consistent with a given category label. We found that, congruent with behavioral completion responses, the visual cortex reinstated the pattern of the missing prototypical feature. Specifically, behavioral and neural completion responses were closer to the previously unseen prototype than to the nearest experienced exemplar. Similar to fMRI signatures of pattern completion into experienced event representations, the cortical completion towards the prototypical feature value covaried with hippocampal activity. Furthermore, hippocampal activity during inference reflected sensitivity to the 2D prototype location, alongside a entorhinal grid-like representation of the two-dimensional concept space. Collectively, our results provide novel insight into the neural underpinnings of concept learning and highlight a potential role of cognitive maps in the retrieval of abstracted information during prototype-based inference.
