Hippocampus-reuniens beta coupling supports goal-directed spatial navigation
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Prefrontal–hippocampal communication, supported by both direct and indirect anatomical pathways, is essential for a range of cognitive functions, including spatial navigation. The midline thalamic nucleus reuniens (RE) has been proposed as a key hub along this indirect pathway, coordinating bidirectional interactions between the hippocampus (HC) and prefrontal cortex (PFC). Here, we investigated functional dynamics within the HC–RE–PFC network as adult male rats learned to navigate a complex maze. Initial behavioral analyses revealed three distinct learning phases: exploration, goal-oriented learning, and efficient navigation. Aligning neural data with subject-specific transitions between these phases uncovered distinct neural signatures associated with each learning phase. Notably, the transition from exploratory to goal-directed behavior was accompanied by the emergence of persistent HC-RE beta-band (15-25Hz) interactions, including elevated beta coherence, theta-beta phase-amplitude coupling, and HC-to-RE Granger causality. The interactions further scaled with navigational efficiency, showing increased HC-RE beta coherence in trials without errors. Together, these findings provide new evidence for dynamic HC–RE interactions during goal-directed navigation and support an emerging view that RE functions as a working memory buffer for route-related information, revealing a potential network mechanism underlying flexible spatial behavior.
Highlights
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Beta-band hippocampus–reuniens coupling emerges during goal-directed navigation.
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PAC between HC theta and RE beta increased during goal learning.
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HC–RE coupling strength increases with navigational efficiency.
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Directional hippocampus-to-reuniens communication emerges during learning
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Reuniens supports hippocampal–prefrontal integration for flexible behavior
Significance Statement
Flexible spatial navigation requires coordinated communication between the hippocampus (HC) and the prefrontal cortex (PFC), yet the thalamic mechanisms coordinating HC-PFC interaction remain poorly understood. This study reveals that the nucleus reuniens (RE) of the midline thalamus plays a critical role in mediating HC-PFC communication during spatial learning. By combining detailed behavioral analysis with simultaneous multi-site electrophysiological recording, we identify beta-band HC–RE coupling as a neural signature of the transition from exploration to goal-directed navigation. The strength and directionality of this interaction tracked improvements in navigational efficiency, revealing a thalamic mechanism for integrating hippocampal output into prefrontal circuits. These findings highlight the RE as a working memory buffer for route-related information and advance our understanding of how thalamic hubs contribute to the circuit-level dynamics underlying flexible behavior.
