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Hippocampo-supramammillary coupling across sleep and wake
M Caneo1, N Espinosa1, G Lazcano1
1Laboratory of Neural Circuits, Departamento de Psiquiatria, Facultad de Medicina, Pontificia Universidad Catolica de Chile, Santiago, Chile.
Scientific Reports
|February 25, 2026
Summary
Hippocampal circuits communicate differently during sleep and wakefulness. This study reveals state-dependent, bidirectional coordination between the hippocampus and subcortical nuclei.
Area of Science:
- Neuroscience
- Systems Neuroscience
- Sleep Research
Background:
- Hippocampal communication with subcortical circuits changes across sleep-wake states.
- The precise dynamics of these interactions are not fully understood.
Purpose of the Study:
- To investigate the bidirectional communication between the dorsal hippocampus (CA1, DG) and limbic subcortical nuclei (SuM, LS) across different sleep-wake states.
- To elucidate the state-dependent mechanisms governing hippocampal-subcortical interactions.
Main Methods:
- Simultaneous recording of neuronal spiking and local field potentials in freely behaving rats.
- Analysis of neural activity during non-rapid eye movement (nREM) sleep, rapid eye movement (REM) sleep, quiet wakefulness, and active wakefulness.
Main Results:
- During quiescent states, hippocampal sharp-wave ripples drove top-down excitation in subcortical areas (LS, SuM).
- Supramammillary nucleus (SuM) activity modulated hippocampal firing in a state-dependent manner, with suppression in CA1 and slower activation in DG.
- During activated states, theta oscillations coordinated circuit activity, with SuM showing state-dependent phase-locking to theta waves in REM sleep.
Conclusions:
- Hippocampal-subcortical communication is bidirectional and state-dependent.
- Quiescent states feature top-down hippocampal output, while activated states involve SuM-mediated bottom-up modulation synchronized by theta oscillations.
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