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Clicking on the blue word to follow the retrieval process of our memory can make us relive the past memory again, and it is also the process of restoring the stored information.
The extraction of memory is neither simply dependent on memory imprints nor cues alone, but is a process based on organic interaction between memory imprint features and extracted clue features.
This can explain that a certain clue extraction fails to successfully restore the memory, but the memory can only be retrieved the second time, and it can also explain why sometimes the memory extracted by the clue is wrong.
The DG area of the hippocampus is a key brain area for memory retrieval.
It is mainly composed of two different types of excitatory neurons: granular cells (GCs) and mossy cells (MCs).
MCs are scattered under the granular cell layer.
There has been a lack of effective methods to distinguish MCs from other neuron types.
On February 16, 2021, Professor Lu Youming of Tongji Medical College of Huazhong University of Science and Technology published an article in Cell Reports.
Through the construction of tools to specifically label moss cells, mice found that the inhibitory neurons of moss cells and granular cell layers in the DG area had synapses.
Touch the connection to regulate the extraction of precise memory.
Immunofluorescence experiments showed that Calb2 can specifically label excitatory lichen cells and Calbindin-2 (Calb2) is specifically expressed in moss cells.
Therefore, the researchers constructed the Calb2-cre tool to label moss cells in mice.
Immunofluorescence experiments found that 96% of Calb2-positive cells overlapped with the 2/3 subunit of the AMPA excitatory receptor, a marker of moss cells.
In addition, Calb2-positive cells hardly overlap with granular cells and inhibitory neuron marker GAD67.
This indicates that Calb2 can specifically label excitatory moss cells.
Studies have shown that the hippocampal DG area is mainly involved in the precise part of spatial memory.
Therefore, the researchers used the touch screen to distinguish between precise memory and non-precise memory to distinguish task behavior.
The behavioral science is divided into two stages.
In the first stage, the mice are trained to touch two squares, one of which is correct, and a sugar reward will be given after the touch (referred to as the correct square in the following).
The second stage is space discrimination training.
At this time, the mouse touches six squares.
When two correct squares are placed four squares apart for training, it is called high separation mode, which detects imprecise memory; When the correct squares are adjacent, it is called low separation mode, which detects accurate spatial memory.
Light-regulated moss cells in the DG area.
Researchers injected the optogenetic virus rAAV1/2-CaMKIIa-DIO-Kir2.
1tdT to inhibit the moss cells in the hippocampal DG area.
After the low-separation mode mice require more inversions to complete the experiment correctly, memory The extraction efficiency is reduced, which indicates that the precise spatial memory is impaired after inhibiting the activity of moss cells.
After light activates moss cells, it can increase the efficiency of precise spatial memory extraction.
Previous studies have shown that granular cells in the DG area mainly integrate information from the outside, while moss cells establish neural connections with granular cells to encode spatial information.
The researchers found that after light-activated moss cells, the discharge activity of granular cells weakened, indicating that moss cells have an inhibitory effect on granular cells.
The granulosa cell layer mainly expresses somatostatin (SST) and paralbumin (pv) inhibitory neurons.
To further clarify the specific connection between moss cells and granule cells, they injected the anterograde tracer virus rAAV1/2-CaM-KIIa-DIO-TKGFP into the DG area of Calb-cre mice and found that it mainly projected to the granule cell layer.
.
Immunofluorescence experiments further showed that the neurons projected to the granular cell layer were mainly SST-ergic neurons.
These results indicate that moss cells exert an inhibitory effect by establishing synaptic connections with SST inhibitory neurons in the granular cell layer.
After photoinhibition of SST neurons, mice’s precise memory was impaired.
Researchers injected the optogenetic virus rAAV1/2-EF1a-DIO-GFP-IRES-Kir2.
1/tdT into the DG area of SST-cre mice.
The precise memory of mice after SST neurons in this area is impaired.
On the other hand, light inhibition of precise memory impairment caused by moss cells can effectively alleviate this memory impairment after activating SST neurons.
This indicates that SST neurons projected by moss cells to the granular cell layer can regulate precise memory.
In summary, this article uses interesting behavioral and specific optogenetic techniques to discover that there are micro-neural circuits in the hippocampus DG that regulate precise memory.
[References] 1.
https://doi.
org/10.
1016/j.
celrep.
2021.
108741, the pictures in the text are all from the references
The extraction of memory is neither simply dependent on memory imprints nor cues alone, but is a process based on organic interaction between memory imprint features and extracted clue features.
This can explain that a certain clue extraction fails to successfully restore the memory, but the memory can only be retrieved the second time, and it can also explain why sometimes the memory extracted by the clue is wrong.
The DG area of the hippocampus is a key brain area for memory retrieval.
It is mainly composed of two different types of excitatory neurons: granular cells (GCs) and mossy cells (MCs).
MCs are scattered under the granular cell layer.
There has been a lack of effective methods to distinguish MCs from other neuron types.
On February 16, 2021, Professor Lu Youming of Tongji Medical College of Huazhong University of Science and Technology published an article in Cell Reports.
Through the construction of tools to specifically label moss cells, mice found that the inhibitory neurons of moss cells and granular cell layers in the DG area had synapses.
Touch the connection to regulate the extraction of precise memory.
Immunofluorescence experiments showed that Calb2 can specifically label excitatory lichen cells and Calbindin-2 (Calb2) is specifically expressed in moss cells.
Therefore, the researchers constructed the Calb2-cre tool to label moss cells in mice.
Immunofluorescence experiments found that 96% of Calb2-positive cells overlapped with the 2/3 subunit of the AMPA excitatory receptor, a marker of moss cells.
In addition, Calb2-positive cells hardly overlap with granular cells and inhibitory neuron marker GAD67.
This indicates that Calb2 can specifically label excitatory moss cells.
Studies have shown that the hippocampal DG area is mainly involved in the precise part of spatial memory.
Therefore, the researchers used the touch screen to distinguish between precise memory and non-precise memory to distinguish task behavior.
The behavioral science is divided into two stages.
In the first stage, the mice are trained to touch two squares, one of which is correct, and a sugar reward will be given after the touch (referred to as the correct square in the following).
The second stage is space discrimination training.
At this time, the mouse touches six squares.
When two correct squares are placed four squares apart for training, it is called high separation mode, which detects imprecise memory; When the correct squares are adjacent, it is called low separation mode, which detects accurate spatial memory.
Light-regulated moss cells in the DG area.
Researchers injected the optogenetic virus rAAV1/2-CaMKIIa-DIO-Kir2.
1tdT to inhibit the moss cells in the hippocampal DG area.
After the low-separation mode mice require more inversions to complete the experiment correctly, memory The extraction efficiency is reduced, which indicates that the precise spatial memory is impaired after inhibiting the activity of moss cells.
After light activates moss cells, it can increase the efficiency of precise spatial memory extraction.
Previous studies have shown that granular cells in the DG area mainly integrate information from the outside, while moss cells establish neural connections with granular cells to encode spatial information.
The researchers found that after light-activated moss cells, the discharge activity of granular cells weakened, indicating that moss cells have an inhibitory effect on granular cells.
The granulosa cell layer mainly expresses somatostatin (SST) and paralbumin (pv) inhibitory neurons.
To further clarify the specific connection between moss cells and granule cells, they injected the anterograde tracer virus rAAV1/2-CaM-KIIa-DIO-TKGFP into the DG area of Calb-cre mice and found that it mainly projected to the granule cell layer.
.
Immunofluorescence experiments further showed that the neurons projected to the granular cell layer were mainly SST-ergic neurons.
These results indicate that moss cells exert an inhibitory effect by establishing synaptic connections with SST inhibitory neurons in the granular cell layer.
After photoinhibition of SST neurons, mice’s precise memory was impaired.
Researchers injected the optogenetic virus rAAV1/2-EF1a-DIO-GFP-IRES-Kir2.
1/tdT into the DG area of SST-cre mice.
The precise memory of mice after SST neurons in this area is impaired.
On the other hand, light inhibition of precise memory impairment caused by moss cells can effectively alleviate this memory impairment after activating SST neurons.
This indicates that SST neurons projected by moss cells to the granular cell layer can regulate precise memory.
In summary, this article uses interesting behavioral and specific optogenetic techniques to discover that there are micro-neural circuits in the hippocampus DG that regulate precise memory.
[References] 1.
https://doi.
org/10.
1016/j.
celrep.
2021.
108741, the pictures in the text are all from the references
