Spatial Representations of Granule Cells and Mossy Cells of the Dentate Gyrus

Highlights

• A decision tree classifier identified putative granule and mossy cells from tetrodes

• Granule cells are rarely active and typically have single firing fields

• Juxtacellularly identified mossy cells have multiple firing fields

• Granule cells and mossy cells differentially encode distinct environments

Summary

Granule cells in the dentate gyrus of the hippocampus are thought to be essential to memory function by decorrelating overlapping input patterns (pattern separation). A second excitatory cell type in the dentate gyrus, the mossy cell, forms an intricate circuit with granule cells, CA3c pyramidal cells, and local interneurons, but the influence of mossy cells on dentate function is often overlooked. Multiple tetrode recordings, supported by juxtacellular recording techniques, showed that granule cells fired very sparsely, whereas mossy cells in the hilus fired promiscuously in multiple locations and in multiple environments. The activity patterns of these cell types thus represent different environments through distinct computational mechanisms: sparse coding in granule cells and changes in firing field locations in mossy cells.