Neuron
Volume 74, Issue 1, 12 April 2012, Pages 57-64
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Hub GABA Neurons Mediate Gamma-Frequency Oscillations at Ictal-like Event Onset in the Immature Hippocampus

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Summary

Gamma-frequency oscillations (GFOs, >40 Hz) are a general network signature at seizure onset at all stages of development, with possible deleterious consequences in the immature brain. At early developmental stages, the simultaneous occurrence of GFOs in different brain regions suggests the existence of a long-ranging synchronizing mechanism at seizure onset. Here, we show that hippocamposeptal (HS) neurons, which are GABA long-range projection neurons, are mandatory to drive the firing of hippocampal interneurons in a high-frequency regime at the onset of epileptiform discharges in the intact, immature septohippocampal formation. The synchronized firing of interneurons in turn produces GFOs, which are abolished after the elimination of a small number of HS neurons. Because they provide the necessary fast conduit for pacing large neuronal populations and display intra- and extrahippocampal long-range projections, HS neurons appear to belong to the class of hub cells that play a crucial role in the synchronization of developing networks.

Highlights

► Long-range projection cells are important for synchronizing γ-frequency oscillations ► Hippocamposeptal cells show a buildup in their synchronization before field GFOs ► HS cells entrain the interneurons' firing, which in turn produces transient GFOs ► Elimination of a small number of hub HS neurons abolishes the expression of GFOs

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These authors contributed equally to this work

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These authors contributed equally to this work