title: Absence of Visual Input Results in the Disruption of Grid Cell Firing in the Mouse.
abstract: Grid cells are spatially modulated neurons within the medial entorhinal cortex whose firing fields are arranged at the vertices of tessellating equilateral triangles [1]. The exquisite periodicity of their firing has led to the suggestion that they represent a path integration signal, tracking the organism's position by integrating speed and direction of movement [2-10]. External sensory inputs are required to reset any errors that the path integrator would inevitably accumulate. Here we probe the nature of the external sensory inputs required to sustain grid firing, by recording grid cells as mice explore familiar environments in complete darkness. The absence of visual cues results in a significant disruption of grid cell firing patterns, even when the quality of the directional information provided by head direction cells is largely preserved. Darkness alters the expression of velocity signaling within the entorhinal cortex, with changes evident in grid cell firing rate and the local field potential theta frequency. Short-term (<1.5 s) spike timing relationships between grid cell pairs are preserved in the dark, indicating that network patterns of excitatory and inhibitory coupling between grid cells exist independently of visual input and of spatially periodic firing. However, we find no evidence of preserved hexagonal symmetry in the spatial firing of single grid cells at comparable short timescales. Taken together, these results demonstrate that visual input is required to sustain grid cell periodicity and stability in mice and suggest that grid cells in mice cannot perform accurate path integration in the absence of reliable visual cues.
authors: Department of Neuroscience, Physiology, and Pharmacology, UCL, Gower Street, London WC1E 6BT, UK. Electronic address: guifen.chen@ucl.ac.uk.
authors: Guifen
authors: G
authors: Chen
authors: Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK; Centre for Mathematics and Physics in the Life Sciences and Experimental Biology, UCL, Gower Place, London WC1E 6BT, UK.
authors: Daniel
authors: D
authors: Manson
authors: Department of Neuroscience, Physiology, and Pharmacology, UCL, Gower Street, London WC1E 6BT, UK. Electronic address: f.cacucci@ucl.ac.uk.
authors: Francesca
authors: F
authors: Cacucci
authors: Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK. Electronic address: t.wills@ucl.ac.uk.
authors: Thomas Joseph
authors: TJ
authors: Wills
mesh_terms: D000818:Animals; D003463:Cues; D003624:Darkness; D018728:Entorhinal Cortex / Q000502:physiology*; D005106:Exploratory Behavior; D000071038:Grid Cells / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D013028:Space Perception / Q000502:physiology*; D014796:Visual Perception