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Click on the blue words to follow our navigation and spatial memory is essential for the survival of wild animals.
When an animal passes through a specific spatial location area, the firing activity of neurons in the hippocampus increases significantly.
These activated neurons are called place fields (PFs).
Different location units will trigger discharge activities at different locations.
Most of the research on spatial memory mainly uses mouse models, and the experiment has a small space for activity, which is far from the navigation of the external environment and the vast space of spatial memory.
Studies have shown that the number of PFs under the experimental conditions is about 30-40% of the total number of cells in the site.
According to simple mathematical calculations, in an experimental environment with a diameter of 10-20 cm, calculations based on the data obtained in mice (the coding pattern of each neuron firing separately) require at least 1 trillion neurons to complete, and this number is at least It is 10 million times the total number of neurons in the CA1 area of the hippocampus.
Mice living in the wild move more than 1 km per night at night.
The flying distance of Egyptian fruit bats can reach about 30 kilometers per night, and its flight area is about 2 kilometers wide and 0.
5 kilometers high.
Therefore, the way of obtaining hippocampal neurons to encode spatial information in a laboratory environment cannot meet the information needs of spatial memory encoding in a wide field environment.
Therefore, there may be a more efficient way of encoding space.
On May 28, 2021, the Nachum Ulanovsky research team of the Weizmann Institute of Science in Israel recorded the activity of neurons at the location of fruit bats in a 200-meter-long flight area in a field environment, revealing an unknown and efficient The method of encoding spatial information: the firing method of a single neuron with multiple regions in a variable range.
The flow chart of the free flight experiment of bats.
The researchers used sixteen-channel wireless neural recording to record the neuron firing activity in the CA1 region of the hippocampus on the dorsal hippocampus of wild Egyptian fruit bats flying in the open air.
They recorded 235 vertebral neurons, which were all captured during the flight.
Activated, 83.
4% of which are positional cells.
The discharge activity of cells in these locations is spatially dependent during flight.
Most of the cells can discharge in different spatial positions.
In addition, the discharge activity is different in different flight directions.
Only a small part of the cells (12.
2%) only discharge in one position.
They found that the areas where cells discharge during flight can be large or small: the large range can reach 32 meters, and the small range can reach 0.
6 meters.
What is even more surprising is that the firing of neurons in the same location is completely different at different locations, and the ratio between the length of the maximum range and the length of the minimum range can reach about 20.
Researchers found that placing fruit bats in a 6-meter-long orbit to simulate an experimental environment, but the location cells do not show the above-mentioned diverse characteristics.
In addition, this diversity of location cells will not change due to the familiarity or unfamiliarity of the flight path of the fruit bats.
Fruit bats raised in the laboratory can also show similar characteristics to survival in the wild after the above-mentioned orbital flight.
Six possible modes of encoding spatial information.
Researchers guess that there are six possible modes of the way these cells encode spatial memory: mode one (single small area discharge); mode two (single large area discharge); mode three (single area) Discharge, the range gradually increases); Mode 4 (multiple areas and small area discharge); Mode 5 (multiple areas, large area and fixed size discharge); Mode 6 (multiple areas and variable range discharge).
The statistical model Bayesian Maximum Likelihood Method is used to evaluate the accuracy of the above models for predicting spatial information, and it is found that under the conditions of a small range of experimental environment, the six models can predict the information well.
But in the open space, only mode 5 and mode 6 can make perfect predictions (mode 6 is more in line with the research data in this article).
These two models can encode spatial information within 1000 meters using less than 50 neurons.
What is the cause of this multi-area discharge characteristic of location cells? The researchers ruled out factors such as the flight speed of the bat and the shape of the flight path, as well as the abnormal discharge of neurons in the vertebral body of the CA1 area.
CA3 and the medial entorhinal cortex (MEC) are the two main input brain areas of CA1: CA3 also has positional cells, and MEC brain areas have grid cells.
The researchers found that the logic of the grid cells did not conform to the supporting experimental data, but the network pattern of input from multiple CA3 location cells with different spatial dimensions to a single CA1 location cell supported the experimental data.
In general, different from the classic spatial information encoding method in a narrow range, this article reveals an efficient encoding method for multi-regional discharge of cells in the hippocampus of a wide environment, which is more adaptable to the changing environment of nature.
[References] 1.
https://doi.
org/10.
1126/science.
abg4020 The pictures in the article are all from the reference original download link: link: https://pan.
baidu.
com/s/16oRXxtLRXA9WFYhC-mjLOQ Extraction code: s4k5
When an animal passes through a specific spatial location area, the firing activity of neurons in the hippocampus increases significantly.
These activated neurons are called place fields (PFs).
Different location units will trigger discharge activities at different locations.
Most of the research on spatial memory mainly uses mouse models, and the experiment has a small space for activity, which is far from the navigation of the external environment and the vast space of spatial memory.
Studies have shown that the number of PFs under the experimental conditions is about 30-40% of the total number of cells in the site.
According to simple mathematical calculations, in an experimental environment with a diameter of 10-20 cm, calculations based on the data obtained in mice (the coding pattern of each neuron firing separately) require at least 1 trillion neurons to complete, and this number is at least It is 10 million times the total number of neurons in the CA1 area of the hippocampus.
Mice living in the wild move more than 1 km per night at night.
The flying distance of Egyptian fruit bats can reach about 30 kilometers per night, and its flight area is about 2 kilometers wide and 0.
5 kilometers high.
Therefore, the way of obtaining hippocampal neurons to encode spatial information in a laboratory environment cannot meet the information needs of spatial memory encoding in a wide field environment.
Therefore, there may be a more efficient way of encoding space.
On May 28, 2021, the Nachum Ulanovsky research team of the Weizmann Institute of Science in Israel recorded the activity of neurons at the location of fruit bats in a 200-meter-long flight area in a field environment, revealing an unknown and efficient The method of encoding spatial information: the firing method of a single neuron with multiple regions in a variable range.
The flow chart of the free flight experiment of bats.
The researchers used sixteen-channel wireless neural recording to record the neuron firing activity in the CA1 region of the hippocampus on the dorsal hippocampus of wild Egyptian fruit bats flying in the open air.
They recorded 235 vertebral neurons, which were all captured during the flight.
Activated, 83.
4% of which are positional cells.
The discharge activity of cells in these locations is spatially dependent during flight.
Most of the cells can discharge in different spatial positions.
In addition, the discharge activity is different in different flight directions.
Only a small part of the cells (12.
2%) only discharge in one position.
They found that the areas where cells discharge during flight can be large or small: the large range can reach 32 meters, and the small range can reach 0.
6 meters.
What is even more surprising is that the firing of neurons in the same location is completely different at different locations, and the ratio between the length of the maximum range and the length of the minimum range can reach about 20.
Researchers found that placing fruit bats in a 6-meter-long orbit to simulate an experimental environment, but the location cells do not show the above-mentioned diverse characteristics.
In addition, this diversity of location cells will not change due to the familiarity or unfamiliarity of the flight path of the fruit bats.
Fruit bats raised in the laboratory can also show similar characteristics to survival in the wild after the above-mentioned orbital flight.
Six possible modes of encoding spatial information.
Researchers guess that there are six possible modes of the way these cells encode spatial memory: mode one (single small area discharge); mode two (single large area discharge); mode three (single area) Discharge, the range gradually increases); Mode 4 (multiple areas and small area discharge); Mode 5 (multiple areas, large area and fixed size discharge); Mode 6 (multiple areas and variable range discharge).
The statistical model Bayesian Maximum Likelihood Method is used to evaluate the accuracy of the above models for predicting spatial information, and it is found that under the conditions of a small range of experimental environment, the six models can predict the information well.
But in the open space, only mode 5 and mode 6 can make perfect predictions (mode 6 is more in line with the research data in this article).
These two models can encode spatial information within 1000 meters using less than 50 neurons.
What is the cause of this multi-area discharge characteristic of location cells? The researchers ruled out factors such as the flight speed of the bat and the shape of the flight path, as well as the abnormal discharge of neurons in the vertebral body of the CA1 area.
CA3 and the medial entorhinal cortex (MEC) are the two main input brain areas of CA1: CA3 also has positional cells, and MEC brain areas have grid cells.
The researchers found that the logic of the grid cells did not conform to the supporting experimental data, but the network pattern of input from multiple CA3 location cells with different spatial dimensions to a single CA1 location cell supported the experimental data.
In general, different from the classic spatial information encoding method in a narrow range, this article reveals an efficient encoding method for multi-regional discharge of cells in the hippocampus of a wide environment, which is more adaptable to the changing environment of nature.
[References] 1.
https://doi.
org/10.
1126/science.
abg4020 The pictures in the article are all from the reference original download link: link: https://pan.
baidu.
com/s/16oRXxtLRXA9WFYhC-mjLOQ Extraction code: s4k5
