GoodSmith, D. | bioRxiv Science

bioRxiv2022

Global remapping in granule cells and mossy cells of the mouse dentate gyrus

Hippocampal place cells exhibit spatially modulated firing, or place fields, which can remap to encode changes in the environment or other variables. Unique among hippocampal subregions, the dentate gyrus (DG) has two excitatory populations of place cells, granule cells and mossy cells, which are among the least and most active spatially modulated cells in the hippocampus, respectively. Previous studies of remapping in the DG have drawn different conclusions about whether granule cells exhibit global remapping and contribute to the encoding of context specificity. By recording granule cells and mossy cells as mice foraged in different environments, we found that by most measures, both granule cells and mossy cells remapped robustly but through different mechanisms that are consistent with firing properties of each cell type. Our results resolve the ambiguity surrounding remapping in the DG and suggest that most spatially modulated granule cells contribute to orthogonal representations of distinct spatial contexts.

neuroscience↗

bioRxiv2021

Flexible encoding of objects and space in single cells of the dentate gyrus

The hippocampus is involved in the formation of memories that require associations among stimuli to construct representations of space and the items and events within that space. Neurons in the dentate gyrus (DG), an initial input region of the hippocampus, have robust spatial tuning, but it is unclear how nonspatial information may be integrated with spatially modulated firing at this stage. We recorded from the DG of 21 adult mice as they foraged for food in an environment that contained discrete objects. By classifying recorded DG cells into putative granule cells and mossy cells, we examined how the addition or displacement of objects affected the spatial firing of these DG cell types. We found DG cells with multiple firing fields at a fixed distance and direction from objects (landmark vector cells) as well as cells that exhibited localized changes in spatial firing when objects in the environment were manipulated. When mice were exposed to a second environment with the same objects, DG spatial maps were completely reorganized, suggesting standard global remapping, and a largely different subset of cells responded to object manipulations. Together, these data reveal the capacity of DG cells to detect small changes in the environment, while preserving a stable spatial representation of the overall context.

neuroscience↗