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Prefrontal-Hippocampal Pathways Through the Nucleus Reuniens Are Functionally Biased by Brain State
Brandon E Hauer1, Silvia Pagliardini1,2,3, Clayton T Dickson1,2,3,4
1Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.
Frontiers in Neuroanatomy
|February 17, 2022
Summary
Brain states significantly alter communication between the prefrontal cortex (PFC) and hippocampus (HPC), with the nucleus reuniens (RE) mediating these changes. This impacts memory consolidation during sleep-like rhythms.
Area of Science:
- Neuroscience
- Systems Neuroscience
- Cognitive Neuroscience
Background:
- Neural circuit communication is vital for central nervous system function.
- Coordinated rhythmic activity between the prefrontal cortex (PFC) and hippocampus (HPC) supports memory.
- The nucleus reuniens (RE) coordinates slow-wave activity between the PFC and HPC.
Purpose of the Study:
- To investigate how PFC-HPC communication is modulated by different brain states (activated theta vs. deactivated slow oscillation).
- To determine the role of the nucleus reuniens (RE) in state-dependent PFC-HPC communication.
Main Methods:
- Utilized urethane anesthesia to induce spontaneous brain state changes.
- Stimulated PFC and RE afferents to assess evoked potentials and current sinks in the HPC.
- Employed optogenetic and chemogenetic techniques to manipulate RE activity.
- Analyzed the phase-dependent modulation of HPC responses.
Main Results:
- Hippocampal responses were larger during slow oscillation (SO) states compared to theta states.
- PFC stimulation during theta preferentially utilized a cortico-cortical pathway over the RE to HPC pathway.
- RE manipulation revealed its role in mediating state-dependent pathway selection.
- The phase of ongoing rhythms modulated HPC responses, with maximal EPSPs during the negative-going phase.
Conclusions:
- Forebrain state critically shapes PFC-HPC communication, with the RE acting as a key modulator.
- Sleep-like rhythms influence neural coordination and excitatory processing in the episodic memory circuit.
- Findings have implications for understanding activity-dependent processes in sleep-dependent memory consolidation.
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