Grid cells fire in multiple locations arranged in a hexagonal symmetry and may provide the ‘spatial metric’ for the hippocampal cognitive map. It is unclear how their grid-like firing patterns are generated, and whether they represent one end of a wider continuum of locational firing patterns or an entirely distinct unique pattern. In this thesis I report a range of spatially periodic firing patterns including canonical grid cells in neuronal populations recorded from the medial entorhinal cortex and adjacent parasubiculum of rats foraging for food in simple enclosures. Two-dimensional spatial Fourier analysis revealed that the firing patterns of many cells of this larger population were composed of a small number of periodic bands. Configurations of periodic bands with a 60º organisation corresponded to grid cells and had the most stable firing properties. Other spatially periodic patterns showed a higher degree of variability in the orientations of their spatial components and significantly diverged from hexagonal symmetry. In general all the components of spatially periodic cells tend to align within each animal regardless of their symmetrical properties. Firing patterns in a single cell occasionally changed between hexagonal and non-hexagonal spatially periodic patterns, pointing to a single mechanism for the formation of the diverse patterns. My results describe a general class of spatially periodic cells in the parahippocampal formation, including grid cells as the most regular and stable, and suggest that they are formed from a restricted set of elemental periodic band-like components.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:626087 |
| Date | January 2013 |
| Creators | Krupic, J. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1385886/ |
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