What’s in a cognitive map? Action representations in the hippocampal-entorhinal system

Spatially selective cell types in the mammalian entorhinal cortex are often taken as building blocks of a ‘cognitive map’, a mental representation of relational information. Nonetheless, relating these representations to behaviour, especially in non-spatial domains, has proven difficult. In this thesis, it will be argued that entorhinal representations of task structure integrate action information in support of flexible behaviour. Moreover, these representations appear connected to gaze behaviour and rotate across task contexts. In a first study, I used functional magnetic resonance imaging (fMRI) to test for an entorhinal representation of learned actions in a conceptual space. To this end, I taught participants to associate numerically labelled states with specific mathematical operations, and examined neural pattern similarity as a function of action distribution similarity. Entorhinal neural pattern similarities scaled with action similarity. Moreover, these representations were tied to gaze behaviour, suggesting a potential link between the use of eye movements to navigate conceptual spaces and structural representations in the entorhinal cortex. To understand these results better, a second study was carried out in which animal images were associated with context-dependent eye movement patterns in two different contexts. Firstly, I replicated the previous finding that the entorhinal cortex represents possible actions, showing that the entorhinal cortex encodes action similarities. Secondly, I tested action across task contexts and found evidence that neural representations rotated across graph contexts. The present work, therefore, demonstrates that representations of relational structure in the entorhinal cortex are tied to action in non-spatial and visuospatial domains. The identified action representations are linked to gaze behaviour and appear to rotate in response to changes in task context.