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Breakthrough Discovery of 2005: Why Grid Cells Became a Star in Neuroscience?
In 2005, Norwegian scientists Edvard Moser, May-Britt Moser and their students discovered a type of nerve cells called grid cells. Yuan, a discovery that revolutionizes our understanding of how the brain is positioned. Grid cells are located in the entorhinal cortex. As animals move through open space, they emit signals at regular intervals at specific locations, helping the animal understand its position in space.
"The discovery of grid cells not only explains how animals navigate, but also reveals the position encoding mechanism in the brain."
This research also enabled the scientists to win the Nobel Prize in Physiology or Medicine in 2014 in recognition of their significant contribution to the discovery of positioning system cells. These cells display a unique spatial firing pattern that encodes a neural representation of Euclidean space and provides a dynamic computational mechanism for self-localization based on continuously updated positional information.
In a typical experiment, researchers implant electrodes into a mouse's dorsal entorhinal cortex and record the activity of individual neurons as the mouse moves freely. When a neuron fires an action potential, the researchers mark the mouse's location on the map, and the marks accumulate over time, forming small clusters that eventually form a grid of equilateral triangles.
"This discovery allows us to understand how spatial memory and navigation are performed in the brain."
Relative to place cells in the mouse hippocampus, grid cells display a regular triangular pattern that makes them stand out in the study. As early as 1971, John O'Keefe and Jonathon Dostrovsky had reported the discovery of place cells, cells that fire action potentials as animals move through specific spaces, Form a similar spatial encoding mechanism.
However, with further research on the entorhinal cortex, the Mosers and their team conducted experiments on grid cells in 2005, finally confirming their existence and function. In the experiments underlying their discovery, they used a larger environment to observe the activity of these cells and found that they actually exhibited a hexagonal grid pattern that remained stable whether in light or in the dark.
"The activity of grid cells does not require visual input, suggesting that they may be related to the spatial mapping that underlies self-motion."
In addition to the internal representation of motion, they work together with head direction cells and joint position-direction cells in the entorhinal cortex to further enhance the brain's capabilities in spatial orientation and navigation. Although many mammals are capable of path integration in the absence of external visual or other sensory cues, the human entorhinal cortex does not appear to be required for this process.
Scientists have suggested that these grid cells may serve multiple functions to support animals' effective navigation in complex environments. For example, by moving between different environments, the patterns of these cells can undergo complete remapping, a process that has important interactions with local cell activity in the hippocampus. When environmental characteristics change significantly, the activity patterns of these cells may shift and rotate unpredictably.
"This shows that interactions between grid cells and place cells provide key insights into the brain's positioning system."
In addition, studies have shown that the activity of grid cells is closely related to theta fluctuations of the hippocampus. This means that these cells play an important role in the brain's computational processes. The grid cell's fire pattern exhibits phase progression as the animal moves through its patterned location, demonstrating its strong interaction with animal activity.
Ultimately, this discovery is not only important for unraveling how the brain processes and understands spatial information, but also inspires a new wave of research into animal learning and memory processes. As grid cells and their functions are further explored, the scientific community is still pondering the far-reaching implications of these findings: Will our future reveal more surprising secrets about the workings of our brains?
