Hippocampal CA3 connectomics reveals a gradient of mossy fiber inputs and selective feedforward inhibition onto pyramidal cells.

Large-scale hippocampal CA3 connectomics reveals a gradient of mossy fiber inputs and specific feedforward inhibition targeting pyramidal cell subtypes.

• Why it matters: Understanding the detailed wiring of mossy fiber connections is crucial for deciphering mechanisms underlying pattern separation, pattern completion, and memory encoding in the hippocampus.
• What they did: The study reconstructed a 3D electron microscopy volume from mouse hippocampal CA3, mapping over 55,000 mossy fiber axons and classifying all neurons, revealing input gradients and inhibitory circuits.
• The result: Findings show pyramidal cells receive more mossy fiber inputs proximally, with some distal cells showing high convergence, and identify a selective feedforward inhibitory circuit, enabling deeper insights into hippocampal function.