Looking at numbers: Evidence for a neural representation of state transitions in the entorhinal and prefrontal cortices
Alexander Eperon1,2 (firstname.lastname@example.org), Christian F. Doeller2,3,4,5, Stephanie Theves2, Roberto Bottini1; 1University of Trento, Italy, 2Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 3Kavli Institute for Systems Neuroscience, Center for Neural Computation, The Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, Jebsen Center for Alzheimer’s Disease, Norwegian University of Science and Technology, Trondheim, Norway, 4Wilhelm Wundt Institute of Psychology, Leipzig University, Germany, 5Technical University Dresden, Germany
Previous work has demonstrated that the hippocampal-entorhinal region is sensitive to the relational structure of experience, in both spatial and non-spatial domains. Within this, the medial entorhinal cortex (MEC) may play a role in generalising task structure across different sensory stimuli and environments. However, it remains unclear how we use our relational memory to guide behaviour: even if we know the states involved in making coffee, to exploit this knowledge we need to know which actions to take. To support this, the entorhinal cortex may map out learned ‘actions’, or transitions, between nodes in a graph structure (like velocity signals in navigation). To test this idea, we carried out an fMRI experiment (n=57) in which participants learned to navigate around a numberline using a set of mathematical operations. This strong linear prior allowed us to test for the similarity of possible actions from each state. Using representational similarity analysis, we find a representation of possible transitions per state in the entorhinal cortex (‘non-spatial affordances’). Concurrently, the medial prefrontal cortex, a region previously associated with action choice, represented the magnitude of possible actions from each state. Importantly, this action code is independent of any other features of the state space, and we believe this to be the first evidence that the entorhinal cortex is involved in the representation of actions in an abstract space. These findings reinforce suggestions from systems and computational neuroscience that medial temporal representations do not just describe our surroundings, but actively guide our behaviour.
Topic Area: LONG-TERM MEMORY: Other
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April 13–16 | 2024