Blog
About

13
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      Structural development and dorsoventral maturation of the medial entorhinal cortex

      Read this article at

      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          We investigated the structural development of superficial-layers of medial entorhinal cortex and parasubiculum in rats. The grid-layout and cholinergic-innervation of calbindin-positive pyramidal-cells in layer-2 emerged around birth while reelin-positive stellate-cells were scattered throughout development. Layer-3 and parasubiculum neurons had a transient calbindin-expression, which declined with age. Early postnatally, layer-2 pyramidal but not stellate-cells co-localized with doublecortin – a marker of immature neurons – suggesting delayed functional-maturation of pyramidal-cells. Three observations indicated a dorsal-to-ventral maturation of entorhinal cortex and parasubiculum: (i) calbindin-expression in layer-3 neurons decreased progressively from dorsal-to-ventral, (ii) doublecortin in layer-2 calbindin-positive-patches disappeared dorsally before ventrally, and (iii) wolframin-expression emerged earlier in dorsal than ventral parasubiculum. The early appearance of calbindin-pyramidal-grid-organization in layer-2 suggests that this pattern is instructed by genetic information rather than experience. Superficial-layer-microcircuits mature earlier in dorsal entorhinal cortex, where small spatial-scales are represented. Maturation of ventral-entorhinal-microcircuits – representing larger spatial-scales – follows later around the onset of exploratory behavior.

          DOI: http://dx.doi.org/10.7554/eLife.13343.001

          eLife digest

          Many animals, from rats to humans, need to navigate their environments to find food or shelter. This ability relies on a kind of memory known as spatial memory, which provides a map of the outside world within the animal’s brain. Specifically, cells in a part of the brain called the medial entorhinal cortex act like the grids present on a map, and are known as grid cells. Other cells in this region represent boundaries in the environment and are known as border cells. These cells and other cells connect to each other to make the spatial memory circuit.

          Previous research had reported that the grid cells were not present in the very early stages of an animal’s life. It was also not clear how the different cell types involved in spatial memory develop after birth. Ray and Brecht have now studied rats and found that certain characteristic structures in the circuit are present at birth. For example, cells that were most likely to become grid cells, were already laid out in a grid, indicating that this layout is instructed by genetic information rather than experience.

          Ray and Brecht also found that the cells that most likely become grid cells matured later than the cells that most likely become border cells. Further analysis then revealed that the circuits in the top part of the medial entorhinal cortex, which represents nearby areas, matured earlier than those in the bottom part of this region, which represent farther areas. These findings could therefore explain why rats explore nearby areas earlier in life before going on to explore further away areas at later stages.

          More work is needed to characterize other components of the neural circuits involved in spatial memory to provide a complete understanding of how these memories are formed. Future experiments could also ask if encouraging young rats to explore a wider area can cause the circuits to mature more quickly.

          DOI: http://dx.doi.org/10.7554/eLife.13343.002

          Related collections

          Most cited references 43

          • Record: found
          • Abstract: found
          • Article: not found

          Microstructure of a spatial map in the entorhinal cortex.

          The ability to find one's way depends on neural algorithms that integrate information about place, distance and direction, but the implementation of these operations in cortical microcircuits is poorly understood. Here we show that the dorsocaudal medial entorhinal cortex (dMEC) contains a directionally oriented, topographically organized neural map of the spatial environment. Its key unit is the 'grid cell', which is activated whenever the animal's position coincides with any vertex of a regular grid of equilateral triangles spanning the surface of the environment. Grids of neighbouring cells share a common orientation and spacing, but their vertex locations (their phases) differ. The spacing and size of individual fields increase from dorsal to ventral dMEC. The map is anchored to external landmarks, but persists in their absence, suggesting that grid cells may be part of a generalized, path-integration-based map of the spatial environment.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Conjunctive representation of position, direction, and velocity in entorhinal cortex.

            Grid cells in the medial entorhinal cortex (MEC) are part of an environment-independent spatial coordinate system. To determine how information about location, direction, and distance is integrated in the grid-cell network, we recorded from each principal cell layer of MEC in rats that explored two-dimensional environments. Whereas layer II was predominated by grid cells, grid cells colocalized with head-direction cells and conjunctive grid x head-direction cells in the deeper layers. All cell types were modulated by running speed. The conjunction of positional, directional, and translational information in a single MEC cell type may enable grid coordinates to be updated during self-motion-based navigation.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              A protein related to extracellular matrix proteins deleted in the mouse mutant reeler.

              The autosomal recessive mouse mutation reeler leads to impaired motor coordination, tremors and ataxia. Neurons in affected mice fail to reach their correct locations in the developing brain, disrupting the organization of the cerebellar and cerebral cortices and other laminated regions. Here we use a previously characterized reeler allele (rl(tg)) to close a gene, reelin, deleted in two reeler alleles. Normal but not mutant mice express reelin in embryonic and postnatal neurons during periods of neuronal migration. The encoded protein resembles extracellular matrix proteins involved in cell adhesion. The reeler phenotype thus seems to reflect a failure of early events associated with brain lamination which are normally controlled by reelin.
                Bookmark

                Author and article information

                Contributors
                Role: Reviewing editor
                Journal
                eLife
                Elife
                eLife
                eLife
                eLife
                eLife Sciences Publications, Ltd
                2050-084X
                02 April 2016
                2016
                : 5
                Affiliations
                deptBernstein Center for Computational Neuroscience , Humboldt University of Berlin , Berlin, Germany
                Boston University , United States
                Boston University , United States
                Author notes
                Article
                13343
                10.7554/eLife.13343
                4876644
                27036175
                © 2016, Ray et al

                This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.

                Product
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/501100002347, Bundesministerium für Bildung und Forschung;
                Award ID: 01GQ1001A
                Award Recipient :
                Funded by: FundRef http://dx.doi.org/10.13039/501100000781, European Research Council;
                Award Recipient :
                Funded by: Gottfried Wilhem Leibniz Prize;
                Award Recipient :
                Funded by: FundRef http://dx.doi.org/10.13039/501100001659, Deutsche Forschungsgemeinschaft;
                Award Recipient :
                Funded by: NeuroCure;
                Award Recipient :
                Funded by: FundRef http://dx.doi.org/10.13039/501100006211, Humboldt-Universität zu Berlin;
                Award Recipient :
                Funded by: Bernstein Center for Computational Neuroscience Berlin;
                Award Recipient :
                The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
                Categories
                Research Article
                Neuroscience
                Custom metadata
                2.5
                The medial entorhinal cortex is important for spatial memory formation and matures from dorsal, where smaller spatial-scales are represented, to ventral, where larger spatial-scales are represented.

                Comments

                Comment on this article