The Hippocampus

2020 ◽  
pp. 166-179
Author(s):  
Frederick L. Coolidge
Keyword(s):  
Spatial Navigation ◽  
Place Cells ◽  
Grid Cells ◽  
Stable Maps ◽  
Olfactory Bulbs ◽  
Additional Stimulation

All mammals have a well-developed hippocampus compared to that of fish, reptiles, and birds, although the latter still have homologous structures. The cells of the hippocampus have differentiated roles: place cells become active and rearrange themselves in new environments, which create new and stable maps of those environments. Grid cells are able to approximate distances, forming an additional neuronal basis for spatial navigation. The hippocampus and olfactory bulbs have intimately related functions. The story of patient H.M. revealed that declarative memories are consolidated by the hippocampus, but procedural memories can be established without hippocampal involvement. Declarative memories remain vulnerable to disruption and forgetting up to about 3 years after memorization. Memories consolidated during sleep are less prone to interference and more stable than memories followed by additional stimulation or learning.

Biomimetic FPGA-based spatial navigation model with grid cells and place cells

2021 ◽  
Author(s):  
Adithya Krishna ◽  
Divyansh Mittal ◽  
Siri Garudanagiri Virupaksha ◽  
Abhishek Ramdas Nair ◽  
Rishikesh Narayanan ◽  
...  
Keyword(s):  
Spatial Navigation ◽  
Place Cells ◽  
Grid Cells

scholarly journals Path integration in place cells of developing rats

2018 ◽  
Vol 115 (7) ◽  
pp. E1637-E1646 ◽  
Author(s):  
Tale L. Bjerknes ◽  
Nenitha C. Dagslott ◽  
Edvard I. Moser ◽  
May-Britt Moser
Keyword(s):  
Path Integration ◽  
Grid Cell ◽  
Cell System ◽  
Place Cells ◽  
Postnatal Life ◽  
Motion Information ◽  
Grid Cells ◽  
Adult Rats ◽  
Self Motion ◽  
Made In

Place cells in the hippocampus and grid cells in the medial entorhinal cortex rely on self-motion information and path integration for spatially confined firing. Place cells can be observed in young rats as soon as they leave their nest at around 2.5 wk of postnatal life. In contrast, the regularly spaced firing of grid cells develops only after weaning, during the fourth week. In the present study, we sought to determine whether place cells are able to integrate self-motion information before maturation of the grid-cell system. Place cells were recorded on a 200-cm linear track while preweaning, postweaning, and adult rats ran on successive trials from a start wall to a box at the end of a linear track. The position of the start wall was altered in the middle of the trial sequence. When recordings were made in complete darkness, place cells maintained fields at a fixed distance from the start wall regardless of the age of the animal. When lights were on, place fields were determined primarily by external landmarks, except at the very beginning of the track. This shift was observed in both young and adult animals. The results suggest that preweaning rats are able to calculate distances based on information from self-motion before the grid-cell system has matured to its full extent.

Grid Cells Lose Coherence in Realistic Environments

2021 ◽  
Author(s):  
Yifan Luo ◽  
Matteo Toso ◽  
Bailu Si ◽  
Federico Stella ◽  
Alessandro Treves
Keyword(s):  
Short Range ◽  
Short Range Order ◽  
Grid Cell ◽  
Place Cells ◽  
Grid Cells ◽  
Lateral Connectivity ◽  
Cell Pattern ◽  
In The Wild ◽  
Freely Moving ◽  
Adaptation Model

Spatial cognition in naturalistic environments, for freely moving animals, may pose quite different constraints from that studied in artificial laboratory settings. Hippocampal place cells indeed look quite different, but almost nothing is known about entorhinal cortex grid cells, in the wild. Simulating our self-organizing adaptation model of grid cell pattern formation, we consider a virtual rat randomly exploring a virtual burrow, with feedforward connectivity from place to grid units and recurrent connectivity between grid units. The virtual burrow was based on those observed by John B. Calhoun, including several chambers and tunnels. Our results indicate that lateral connectivity between grid units may enhance their “gridness” within a limited strength range, but the overall effect of the irregular geometry is to disable long-range and obstruct short-range order. What appears as a smooth continuous attractor in a flat box, kept rigid by recurrent connections, turns into an incoherent motley of unit clusters, flexible or outright unstable.

scholarly journals From grid cells to place cells with realistic field sizes

PLoS ONE ◽  
2017 ◽  
Vol 12 (7) ◽  
pp. e0181618 ◽  
Author(s):  
Torsten Neher ◽  
Amir Hossein Azizi ◽  
Sen Cheng
Keyword(s):  
Place Cells ◽  
Grid Cells

scholarly journals Functional connectivity of the entorhinal–hippocampal space circuit

2014 ◽  
Vol 369 (1635) ◽  
pp. 20120516 ◽  
Author(s):  
Sheng-Jia Zhang ◽  
Jing Ye ◽  
Jonathan J. Couey ◽  
Menno Witter ◽  
Edvard I. Moser ◽  
...  
Keyword(s):  
Entorhinal Cortex ◽  
Cell Types ◽  
Place Cells ◽  
Projection Neurons ◽  
Border Cells ◽  
Head Direction ◽  
Grid Cells ◽  
Head Direction Cells ◽  
Dynamic Interactions ◽  
Cell Groups

The mammalian space circuit is known to contain several functionally specialized cell types, such as place cells in the hippocampus and grid cells, head-direction cells and border cells in the medial entorhinal cortex (MEC). The interaction between the entorhinal and hippocampal spatial representations is poorly understood, however. We have developed an optogenetic strategy to identify functionally defined cell types in the MEC that project directly to the hippocampus. By expressing channelrhodopsin-2 (ChR2) selectively in the hippocampus-projecting subset of entorhinal projection neurons, we were able to use light-evoked discharge as an instrument to determine whether specific entorhinal cell groups—such as grid cells, border cells and head-direction cells—have direct hippocampal projections. Photoinduced firing was observed at fixed minimal latencies in all functional cell categories, with grid cells as the most abundant hippocampus-projecting spatial cell type. We discuss how photoexcitation experiments can be used to distinguish the subset of hippocampus-projecting entorhinal neurons from neurons that are activated indirectly through the network. The functional breadth of entorhinal input implied by this analysis opens up the potential for rich dynamic interactions between place cells in the hippocampus and different functional cell types in the entorhinal cortex (EC).

Place cells, neocortex and spatial navigation: a short review

2003 ◽  
Vol 97 (4-6) ◽  
pp. 537-546 ◽  
Author(s):  
Bruno Poucet ◽  
Pierre-Pascal Lenck-Santini ◽  
Vietminh Paz-Villagrán ◽  
Etienne Save
Keyword(s):  
Spatial Navigation ◽  
Short Review ◽  
Place Cells
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