Curved geometry shapes the observability of hippocampal oscillations

Theta oscillations in the hilus of the folded dentate gyrus are locally masked by cancellation of phase-coherent contributions, despite strong field potentials there.

• Why it matters: Poor theta expression in the hilus is paradoxical given its large field potentials, and curved geometry can obscure which generators produce observed oscillations.
• What they did: Laminar recordings across both hippocampi were combined with computational modeling to test how CA1 and dentate gyrus generators’ volume-conducted fields interact in the hilus.
• The result: CA1 and DG theta generators produce opposite dipolar orientations in the hilus, causing regional cancellation, while beta and gamma remain prominent due to weak coordination across hippocampi.

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