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Free keywords:
Action Potentials
Animals
CA1 Region, Hippocampal/cytology/*physiology
CA3 Region, Hippocampal/cytology/physiology
*Goals
Male
Maze Learning
Midline Thalamic Nuclei/cytology/physiology
Neural Pathways/*physiology
Neurons/physiology
Optogenetics
Prefrontal Cortex/cytology/*physiology
Rats
Rats, Long-Evans
Spatial Navigation/*physiology
Thalamus/cytology/*physiology
Abstract:
Spatial navigation requires information about the relationship between current and future positions. The activity of hippocampal neurons appears to reflect such a relationship, representing not only instantaneous position but also the path towards a goal location. However, how the hippocampus obtains information about goal direction is poorly understood. Here we report a prefrontal-thalamic neural circuit that is required for hippocampal representation of routes or trajectories through the environment. Trajectory-dependent firing was observed in medial prefrontal cortex, the nucleus reuniens of the thalamus, and the CA1 region of the hippocampus in rats. Lesioning or optogenetic silencing of the nucleus reuniens substantially reduced trajectory-dependent CA1 firing. Trajectory-dependent activity was almost absent in CA3, which does not receive nucleus reuniens input. The data suggest that projections from medial prefrontal cortex, via the nucleus reuniens, are crucial for representation of the future path during goal-directed behaviour and point to the thalamus as a key node in networks for long-range communication between cortical regions involved in navigation.
