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

Abstract

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 inthe dentate gyrus, the mossy cell, forms an intricate circuit with granule cells, CA3c pyramidal cells, andlocal 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 firedvery sparsely, whereas mossy cells in the hilus fired promiscuously in multiple locations and in multiple environments. The activity patterns of these cell typesthus represent different environments through distinct computational mechanisms: sparse coding in granule cells and changes in firing field locations in mossy cells.