The lateral entorhinal cortex (LEC) is a major cortical input area to the hippocampus, and it is crucial for asso-ciative object-place-context memories. An unresolved question is whether these associations are perform...
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The lateral entorhinal cortex (LEC) is a major cortical input area to the hippocampus, and it is crucial for asso-ciative object-place-context memories. An unresolved question is whether these associations are performed exclusively in the hippocampus or also upstream of it. Anatomical evidence suggests that the LEC processes both object and spatial information. We describe here a gradient of spatial selectivity along the antero-posterior axis of the LEC. We demonstrate that the LEC generates distinct spatial maps for different contexts that are independent of object coding and vice versa, thus providing evidence for pure spatial and pure object codes upstream of the hippocampus. While space and object coding occur by and large separately in the LEC, we identified neurons that encode for space and objects conjunctively. Together, these findings point to a scenario in which the LEC sustains both distinct space and object coding and associative space-object coding.
Neuroimaging studies have shown that brain activity is variable and changes according to stimuli and the environmental context, reflecting brain coding or information representations at different processing levels. Ho...
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Neuroimaging studies have shown that brain activity is variable and changes according to stimuli and the environmental context, reflecting brain coding or information representations at different processing levels. However, little is known about activity organization that reflects coding strategies. Here, we explored and compared two different coding approaches, spatial via cross-correlation and intensity-based coding using mutual information. Using two fMRI datasets and different seeds, we searched for the spatial and intensity-based sim-ilarities with the seeds in brain activity. Our results showed that, apart from the seed regions, significant regions detected by intensity-based similarity analysis differ completely from those found using cross-correlation. These findings may indicate that information shared through spatial coding differs from that transmitted via non-spatial coding processes. Our results suggest that brain coding is organized in several different ways to opti-mize information processing.
The medial entorhinal cortex (MEC) is part of the brain's network for dynamic representation of location. The most abundant class of neurons in this circuit is the grid cell, characterized by its periodic, hexagon...
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The medial entorhinal cortex (MEC) is part of the brain's network for dynamic representation of location. The most abundant class of neurons in this circuit is the grid cell, characterized by its periodic, hexagonally patterned firing fields. While in developing animals some MEC cell types express adult-like firing patterns already on the first exposure to an open spatial environment, only days after eye opening, grid cells mature more slowly, over a 1-to-2-wk period after the animals leave their nest. Whether the later emergence of a periodic grid pattern reflects a need for experience with spatial environments has not been determined. We here show that grid-like firing patterns continue to appear during exploration of open square environments in rats that are raised for the first months of their life in opaque spherical environments, in the absence of stable reference boundaries to guide spatial orientation. While strictly periodic firing fields were initially absent in these animals, clear grid patterns developed after only a few trials of training. In rats that were tested in the same open environment but raised for the first months of life in opaque cubes, with sharp vertical boundaries, grid-like firing was from the beginning indistinguishable from that of nondeprived control animals growing up in large enriched cages. Thus, although a minimum of experience with peripheral geometric boundaries is required for expression of regular grid patterns in a new environment, the effect of restricted spatial experience is overcome with short training, consistent with a preconfigured experience-independent basis for the grid pattern.
The representation of an animal's position in the medial entorhinal cortex (MEC) is distributed across several modules of grid cells, each characterized by a distinct spatial scale. The population activity within ...
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The representation of an animal's position in the medial entorhinal cortex (MEC) is distributed across several modules of grid cells, each characterized by a distinct spatial scale. The population activity within each module is tightly coordinated and preserved across environments and behavioral states. Little is known, however, about the coordination of activity patterns across modules. We analyzed the joint activity patterns of hundreds of grid cells simultaneously recorded in animals that were foraging either in the light, when sensory cues could stabilize the representation, or in darkness, when such stabilization was disrupted. We found that the states of different modules are tightly coordinated, even in darkness, when the internal representation of position within the MEC deviates substantially from the true position of the animal. These findings suggest that internal brain mechanisms dynamically coordinate the representation of position in different modules, ensuring that they jointly encode a coherent and smooth trajectory.
The medial entorhinal cortex (MEC) creates a map of local space, based on the firing patterns of grid, head-direction (HD), border, and object-vector (OV) cells. How these cell types are organized anatomically is deba...
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The medial entorhinal cortex (MEC) creates a map of local space, based on the firing patterns of grid, head-direction (HD), border, and object-vector (OV) cells. How these cell types are organized anatomically is debated. In-depth analysis of this question requires collection of precise anatomical and activity data across large populations of neurons during unrestrained behavior, which neither electrophysiological nor previous imaging methods fully afford. Here, we examined the topographic arrangement of spatially modulated neurons in the superficial layers of MEC and adjacent parasubiculum using miniaturized, portable two-photon microscopes, which allow mice to roam freely in open fields. Grid cells exhibited low levels of co-occurrence with OV cells and clustered anatomically, while border, HD, and OV cells tended to intermingle. These data suggest that grid cell networks might be largely distinct from those of border, HD, and OV cells and that grid cells exhibit strong coupling among themselves but weaker links to other cell types.
Early theories and methodologies for the spatial representation of geographical objects are tightly related with map projections,and have being developed in the planar mode of map *** are fissure,deformation and topol...
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Early theories and methodologies for the spatial representation of geographical objects are tightly related with map projections,and have being developed in the planar mode of map *** are fissure,deformation and topology errors in the representation of meso-scale to large-scale spatial objects spanning projection *** is not until the 80's in the 20th century that the Global Discreted Grid (GDG) based on polygon discretion and the global surface data model were *** limitations of map projection were shaking off gradually,and the deformation of angular,length,area and the discontinuous of spatial data resulted from map projection are hence ***,the GDG is only served for surface discretion,not for the integral 3D space inside and outside the global *** GDG cannot represent the meso-scale to large-scale spatial objects and phenomena spanning projection zones and/or spanning *** include the relatively static objects such as ocean water body,polar region iceberg,underground tectonic structures,geomagnetism field and geothermal field,and the dynamic objects such as cloud system/cluster,ocean current,atmosphere circulation and monsoon wind *** phenomena include the mass-energy exchange such as global carbon circle,water circle,magnetic field and thermal field spanning ***,with the increase of global change and Earth system sciences research requirements,and with the rapid development of super computation capability,people are seeking for an integral 3D spatial framework and data model for Earth system based on spheroid or ellipsoid. Based on global 3D spatial division,QuaPA coding and degraded octree,the authors have extended GDG to the insides and outside of global surface and have advanced a new global 3D spatial grid,i.e.,Spheroid Degenerated-Octree Grid(SDOG),as in *** radial size,the minimum volume,the maximum volume,and the volume ratio of maximum to minimum of SDOG units in the same level
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