Title Page
Abstract
Contents
Background 12
1. Anatomical structures of the Hippocampal system and their proposed roles 13
2. The remapping properties of Hippocampal place cell 18
3. The usage of the virtual reality (VR) system for rodents in studying the hippocampus 27
Chapter 1. Visual scene stimulus exerts dominant control over the place fields in the virtual reality system 30
Introduction 31
Materials and methods 33
Results 48
Discussion 64
Chapter 2. The functional role of the CA1 and CA3 in processing the visually modified environment 67
Introduction 68
Materials and methods 70
Results 74
Discussion 105
General Discussion 109
Bibliography 122
국문초록 148
Table 1. Hippocampal remapping literature 24
Figure 1. Basic circuit of the hippocampus. 17
Figure 2. VR setup. 36
Figure 3. Two visually enriched virtual environments. 40
Figure 4. Recordings of CA1 and CA3 place cells with tetrodes. 42
Figure 5. Averaged velocity and the place cell activity in the virtual environment. 48
Figure 6. Representative examples of place fields from the City and Forest, respectively. 49
Figure 7. The sensory-motor gain manipulation. 50
Figure 8. Center-of-mass (COM) from both baseline and 2x gain conditions for individual place fields. 51
Figure 9. The auditory contextual switch manipulation. 52
Figure 10. Population vector correlation matrix (PVM) and its linearized graphs from the CA1 (A) or CA3 (B). 54
Figure 11. The proportion of place cells from CA1 and CA3 in the virtual environments. 56
Figure 12. The basic firing properties in the visual enriched virtual environments. 57
Figure 13. Population rate maps from CA1 and CA3. 59
Figure 14. Distribution of Center-of-mass (COM) of the place field CA1 and CA3. 61
Figure 15. The proportion of pauses during the navigation. 63
Figure 16. Adding visual noise to the environments. 71
Figure 17. Sample screen-captured scenes taken at the start location of each visually enriched environment under different fog conditions (0%,... 75
Figure 18. Example of a place cell the fog session. 77
Figure 19. Representative neural firing patterns of single units recorded from CA1 (A) and CA3 (B). 78
Figure 20. More examples of place cells in CA1 (A) and CA3 (B) subregions in the fog manipulation session. 79
Figure 21. Correlation coefficients between rate maps for pre-fog and each fog condition for CA1 and CA3 cells. 80
Figure 22. The cumulative distribution of spatial correlation for each comparison. 81
Figure 23. Representative neural firing patterns of single units recorded from the visual cortex (lateral extrastriate visual cortex; V2L). 82
Figure 24. The spike waveforms of a single unit before and after the recording session. 83
Figure 25. Proportions of stable versus global remapping cells in CA1 and CA3. 85
Figure 26. The Proportions of stable versus global remapping cells in CA1 along with the sampling location. 86
Figure 27. Adding visual noise to a familiar environment affected attention level of animals. 88
Figure 28. Temporal neural dynamics of the place cell in the fog session. 90
Figure 29. Abrupt global remapping is followed by a gradual increase of the firing rate in CA1 with the introduction of fog trials. 91
Figure 30. Global remapping cells in CA1 is shaped by fog experiences. 92
Figure 31. Global remapping and rate remapping subpopulations of place cells in CA1 code distinct types of changes in the environment. 95
Figure 32. Aligned rate maps and PVMs of stable place cells in CA3. 96
Figure 33. The proportion of the globally remapping cells for each session. 97
Figure 34. Each remapping type exhibits coherent patterns across the individual animals. 100
Figure 35. Normalized firing rates of place cells for each fog condition. 102
Figure 36. Schematic illustration of the global remapping and rate remapping (stable) place cells in CA1 and CA3 in fog manipulation sessions. 103
Figure 37. Working model of the hippocampal system in the mismatched condition. 111