-
Categories
-
Pharmaceutical Intermediates
-
Active Pharmaceutical Ingredients
-
Food Additives
- Industrial Coatings
- Agrochemicals
- Dyes and Pigments
- Surfactant
- Flavors and Fragrances
- Chemical Reagents
- Catalyst and Auxiliary
- Natural Products
- Inorganic Chemistry
-
Organic Chemistry
-
Biochemical Engineering
- Analytical Chemistry
-
Cosmetic Ingredient
- Water Treatment Chemical
-
Pharmaceutical Intermediates
Promotion
ECHEMI Mall
Wholesale
Weekly Price
Exhibition
News
-
Trade Service
Introduction: Mind wandering or daydreaming is often considered a state of inattention, especially for patients with depression
.
But daydreaming also has its positive effect – helping people to relax for a short time and to develop their creativity
.
Recently, researchers have found that when this common and frequent psychological phenomenon occurs, communication between the hippocampus and the neocortex is relatively strengthened, which contributes to the strengthening
of memory-related connections.
The hippocampus is located between the cerebral thalamus and the medial temporal lobe, with one in the left and right hemispheres, named for its shape like the hippocampus, also known as the hippocampal gyrus, hippocampus
.
Past studies have shown that the hippocampus is mainly responsible for learning and memory, such as a knowledge concept or event experience is repeatedly mentioned in a short period of time, and the hippocampus will transfer it to the cerebral cortex to form permanent memory
.
The hippocampus also has a certain spatial positioning role, and if it is damaged, it will lead to poor
imagination.
In 1957, two Canadian doctors, Scoville and Milner, reported a classic case
.
The patient, H.
M.
, a motorized coil winder, performed medial temporal lobectomy on both sides of the hippocampus when he was 27
years old because medication could not control his epilepsy symptoms.
After surgery, H.
M.
's epilepsy symptoms were effectively controlled, but severe amnesia symptoms
appeared.
H.
M.
can still remember what happened in his early years and can form new procedural memories (such as how to ride a bicycle, know how to swim after getting into the water, and learn to skillfully draw pentagrams in front of hands and drawings in the mirror), but not new declarative memories (such as remembering what his home address is, what he ate for dinner last time, and his training experience in drawing pentagrams in the mirror).
This case led to the realization that the hippocampus plays an important role
in memory.
By 2003, scientists at Harvard University and New York University had jointly published a new study of the hippocampus, formally identifying the hippocampus as "the main region that helps humans process declarative memories.
"
before the responseThe researchers recorded the response potential
of RSC to SWR on all layers of neurons on the dorsal RSC of awake mice.
The results observed that the potential of 63% of the cells underwent a slow slope drift within a time window of 1-2 seconds before SWR, and most of the cells had a slope drift of hyperpolarization (deepening of the degree of negative potential within the cell membrane).
The response amplitude during SWR is small
.
Similar results were obtained from measurements of dorsal RSC layer 2/3/5 (L2/3/5) cells and imaging of calcium ions in dendritic cells of RSC layer 1 (L1) cells, with pre-SWR silencing most evident
in L1 dendritic clusters.
.
The results showed that in awake mice, input from the thalamus partially drove L1 neurons, and the silence of the thalamus was also sufficient to silence L1 neurons, that is, L1 neurons were able to "copy" input changes
in the thalamus.
Cortical regions outside RSC are also innervated by the thalamus, leading the researchers to speculate that L1 cells outside RSC also show pre-SWR silence
.
Imaging results confirm this hypothesis
.
The decrease in the activity of inhibitory neurons (L1 is both inhibitory neurons) in the surface of the RSC with the silencing of the thalamus is not an isolated phenomenon, but is ubiquitous in the
entire cortex.
Summary The researchers speculate that the thalamus has a dual effect on the reduction of input to the surface layer of the RSC: (1) this silence makes the thalamus temporarily lose the function of afferent signals, reducing interference with weak cortical-cortical interactions; (2) The silencing of the thalamus and other possible subcortical inputs weakens
dendritic inhibition.
These effects may explain how the hippocampus's "whisper" successfully strengthens neocortical connections
during SWR.
Written by| Wind is standing up all night
.
But daydreaming also has its positive effect – helping people to relax for a short time and to develop their creativity
.
Recently, researchers have found that when this common and frequent psychological phenomenon occurs, communication between the hippocampus and the neocortex is relatively strengthened, which contributes to the strengthening
of memory-related connections.
The hippocampus is located between the cerebral thalamus and the medial temporal lobe, with one in the left and right hemispheres, named for its shape like the hippocampus, also known as the hippocampal gyrus, hippocampus
.
Past studies have shown that the hippocampus is mainly responsible for learning and memory, such as a knowledge concept or event experience is repeatedly mentioned in a short period of time, and the hippocampus will transfer it to the cerebral cortex to form permanent memory
.
The hippocampus also has a certain spatial positioning role, and if it is damaged, it will lead to poor
imagination.
In 1957, two Canadian doctors, Scoville and Milner, reported a classic case
.
The patient, H.
M.
, a motorized coil winder, performed medial temporal lobectomy on both sides of the hippocampus when he was 27
years old because medication could not control his epilepsy symptoms.
After surgery, H.
M.
's epilepsy symptoms were effectively controlled, but severe amnesia symptoms
appeared.
H.
M.
can still remember what happened in his early years and can form new procedural memories (such as how to ride a bicycle, know how to swim after getting into the water, and learn to skillfully draw pentagrams in front of hands and drawings in the mirror), but not new declarative memories (such as remembering what his home address is, what he ate for dinner last time, and his training experience in drawing pentagrams in the mirror).
This case led to the realization that the hippocampus plays an important role
in memory.
By 2003, scientists at Harvard University and New York University had jointly published a new study of the hippocampus, formally identifying the hippocampus as "the main region that helps humans process declarative memories.
"
Figure 1 Location of the hippocampus (Source: Wikipedia)
According to the classical model of memory consolidation, the hippocampus is repeatedly activated during sleep and quiet wakefulness to reinforce memory traces in neocortical circuits
.
This reactivation occurs during
sharp-wave ripples (SWRs) in the hippocampus.
Sharp ripples are instantaneous high-frequency oscillations spontaneously released by the hippocampus that can occur during slow-wave sleep and awakening
.
The retrosplenial cortex (RSC) is an important output object
of the hippocampus.
Because the posterior cortex connects the hippocampus to other areas of the cortex, it is thought to play a role
in coordinating the hippocampus and neocortex.
To investigate how the post-compression cortex helps process SWR-related inputs, the researchers recorded neuronal potentials in awake mice and found that membrane potential regulation aligned with SWR was common but weak, and pulse emission was very rare
.
So how does the brain hear this "murmur" from the hippocampus? Researchers at the University of Oslo found that for a second or two before SWR, most areas of the brain become silent so that the rest of the brain can better "listen" to what
the hippocampus is saying.
The results were published in Cell Reports (Figure 2) [1] under the title "Cell-type-specific silence in thalamocortical circuits precedes hippocampal sharp-wave ripples.
"
Figure 2 Research results (Source: [1])
Research shows that:
01 A weak response to SWR is widely present in RSC, and there is often a hyperpolarization processbefore the responseThe researchers recorded the response potential
of RSC to SWR on all layers of neurons on the dorsal RSC of awake mice.
The results observed that the potential of 63% of the cells underwent a slow slope drift within a time window of 1-2 seconds before SWR, and most of the cells had a slope drift of hyperpolarization (deepening of the degree of negative potential within the cell membrane).
The response amplitude during SWR is small
.
Similar results were obtained from measurements of dorsal RSC layer 2/3/5 (L2/3/5) cells and imaging of calcium ions in dendritic cells of RSC layer 1 (L1) cells, with pre-SWR silencing most evident
in L1 dendritic clusters.
Fig.
3 Recording and results of RSC response potential to SWR (Source: [1])
The researchers further imaged neurons in L1 (both inhibitory) and L/2/3 inhibitory neurons that control the degree of dendritic excitability in pyramidal cells, and showed that the proportion of cells with reduced pre-SWR excitability was always higher in all types of cells than in cells with increased excitability (Figure 4).
Fig.
4 Pre-SWR silencing is more prevalent in inhibitory neurons (Source: [1])
Because pre-SWR silencing is prevalent in pyramidal neuronal dendrites and inhibitory neurons, the researchers hypothesized that the thalamus is a common source of this silencing and should therefore also show pre-SWR silencing
.
Imaging results show a significant decrease in thalamic projection activity to L1 before and after SWR onset (Figure 5).
The thalamic-cortical axons projected towards L1 also exhibit pre-SWR silence (source: [1]).
.
The results showed that in awake mice, input from the thalamus partially drove L1 neurons, and the silence of the thalamus was also sufficient to silence L1 neurons, that is, L1 neurons were able to "copy" input changes
in the thalamus.
Cortical regions outside RSC are also innervated by the thalamus, leading the researchers to speculate that L1 cells outside RSC also show pre-SWR silence
.
Imaging results confirm this hypothesis
.
The decrease in the activity of inhibitory neurons (L1 is both inhibitory neurons) in the surface of the RSC with the silencing of the thalamus is not an isolated phenomenon, but is ubiquitous in the
entire cortex.
Summary The researchers speculate that the thalamus has a dual effect on the reduction of input to the surface layer of the RSC: (1) this silence makes the thalamus temporarily lose the function of afferent signals, reducing interference with weak cortical-cortical interactions; (2) The silencing of the thalamus and other possible subcortical inputs weakens
dendritic inhibition.
These effects may explain how the hippocampus's "whisper" successfully strengthens neocortical connections
during SWR.
Fig.
6 Decrease in thalamic cortical input and inhibition promotes the propagation of SWR-related activities in pyramidal dendrites (Source: [1])
Animals intermittently withdraw from their surrounding sensory environment during waking hours — such as daydreaming — and this state shift is accompanied by changes in cortical activity, causing the cortex to functionally separate from subcortical structures from time to time, which may allow the cortex to be more focused on memory shaping
without environmental disturbances.
However, the study did not explore memory-related behavioral tasks, and further research is needed to prove whether thalamic silencing and its effects in RSC are necessary
for memory consolidation.
Written by| Wind is standing up all night
The typography | the night is on the spot
End
Resources:
[1] Chambers,
A.
R.
, C.
N.
Berge, and K.
Vervaeke, Cell-type-specific silence in
thalamocortical circuits precedes hippocampal sharp-wave ripples.
Cell Rep,
2022.
40(4): p.
111132.
