Representation of navigational goals in the orbitofrontal cortex

Raunak Basu
Max Planck Institute for Brain Research, Frankfurt am Main

Abstract
Planning a journey to a goal destination requires representation of the future goal, knowledge about the current location, and a spatial map where the relative geometry between the current and future location is preserved. While neurons in the hippocampus and parahippocampal regions provide estimates of the animal’s current position and nearby trajectories, a specific neural code of the remote navigational goals remains to be identified. We hypothesized that the future goal location might be represented in a brain region outside the hippocampal-entorhinal system, like the orbitofrontal cortex (OFC), which has been implicated in representing decisions in non-spatial tasks. To test our hypothesis, we designed a linear track with multiple reward sites, in which rats were trained to alternate between two given sites to obtain rewards. After few successful alternations, the reward sites are changed to new locations, thereby ensuring continuous update of goal representation. As rats performed this task, we simultaneously recorded the activity of hundreds of OFC neurons. Analysis of the neural activity revealed that OFC neural ensembles exhibit distinct firing patterns at the different reward locations in the maze, thereby encoding the animal’s positions during reward consumption. However, after reward consumption and just before the onset of navigation, these neurons exhibit a representational transition from the animal’s current position to the next goal, which is persistently and dynamically maintained during the entire journey until the animal reaches the destination. Finally, optogenetic perturbation of OFC neurons, specifically at the navigation onset, caused animals to navigate to an incorrect destination, pointing to OFC as part of the brain’s internal map representing the animal’s decision of navigational goals.

Invited by Jérôme Epsztein

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