Summary: Astrocytes, non-neuronal brain tissue, have been shown to work alongside cells to keep and remember thoughts, reshaping our knowledge of storage systems. Researchers discovered that particular astrocytes express the c-Fos protein during the formation of memories, which affects neuronal communication and memory storage. This finding highlights astrocytes ‘ special, memory-specific functions and suggests possible new avenues for treating memory-related problems.
Important Information:
- Astrocytes, much thought to generally help cells, play an active part in remembrance storage and recall.
- In mice, activating memory-linked astrocytes resulted in recall, which suggests that astrocytes can affect memory retrieval in their own way.
- In memory-linked astrocytes, suppressing NFIA prevented a particular memory remember without affecting other thoughts.
Origin: Baylor College of Medicine
A study published in , Nature , by academics at Baylor College of Medicine changes the way we understand storage.
The brain’s cells, which respond to learning events and regulate storage recall, have previously been responsible for memory formation.
The Baylor group expanded this concept by showing that non-neuronal body types in the mind called , astrocytes – star-shaped cells – , even shop memories , and work in concert with groups of neurons called engrams to govern storage , and retrieval of memories.
” The prevalent idea is that the formation and recall of thoughts just involves cerebral engrams that are activated by specific activities, and hold and retrieve a memory”, said corresponding author , Dr. Benjamin Deneen, professor and Dr. Russell J. and Marian K. Blattner Chair in the Department of , Neurosurgery, director of the , Center for Cancer Neuroscience, a member of the , Dan L Duncan Comprehensive Cancer Center , at Baylor and a principal analyst at the , Jan and Dan Duncan Neurological Research Institute.
Our laboratory has been studying astrocytes and their interactions with neurons for a long time. We have discovered that these cells interact with one another physically and functionally, which is crucial for proper brain function. However, the role of astrocytes in memory retrieval and storage has not previously been studied,” Deneen said.
Astrocytes trigger memory recall
The researchers started by creating brand-new laboratory tools to track down and examine the astrocyte activity in memory-brain circuits.
A typical experiment consisted of, first, conditioning mice to feel fear and ‘ freeze’ after exposure to a certain situation. After a while, mice would freeze because they remembered being put back in the same position. Because it’s not the original setting in which the same mice were conditioned to feel fear, they would n’t freeze if they were placed in a different situation.
” Working with these mice and with our new lab tools, we were able to show that astrocytes do play a role in memory recall”, said co-first author , Dr. Wookbong Kwon, a postdoctoral associate in the , Deneen lab.
The researchers show that during learning events, such as fear conditioning, a subset of astrocytes in the brain expresses the c-Fos gene. In that area of the brain, c-Fos-expressing astrocytos regulate circuit activity.
” The c-Fos-expressing astrocytes are physically close with engram neurons”, said co-first author , Dr. Michael R. Williamson, a postdoctoral associate in the Deneen lab.
” Furthermore, we discovered that engram neurons and the astrocyte ensemble that are physically related are also functionally connected. The corresponding neuron engram’s synaptic activity or communication is specifically stimulated by activating the astrocyte ensemble. This astrocyte-neuron communication flows both ways, astrocytes and neurons depend on each other”.
Mice did not freeze when they were in a situation without fear.
” However, when the astrocyte ensemble in these mice in the non-fearful environment was activated, the animals froze, showing that astrocyte activation stimulates memory recall”, Kwon said.
The researchers studied the gene NFIA to better understand what drives the astrocyte ensembles ‘ memory recall activity.
Although astrocytic NFIA has previously demonstrated that it can regulate memory circuits, Williamson said it is not known whether it works with ensembles of astrocytes to control memory storage and recall.
The team discovered that inhibiting NFIA production in astrocytes that are activated by learning events impairs memory recall. Importantly, this suppression is memory specific.
When we removed the NFIA gene from astrocytes that were present during learning events, the animals were able to recall other memories as well, according to Kwon.
These findings “test the nature of the function of astrocytes in memory,” Deneen said.
” Ensembles of learning-associated astrocytes are specific to that learning event. The ensemble of neurons and astrocyte ensembles that control the recall of a fearful experience are also different from those involved in recalling a different learning experience.
The current study provides a more in-depth understanding of the participants and the brain’s processes during memory formation and recall. In addition, the study provides a new perspective when studying human conditions associated with memory loss, like Alzheimer’s disease, as well as conditions in which memories occur repeatedly and are difficult to suppress, like post-traumatic stress disorder.
Junsung Woo, Yeunjung Ko, Ehson Maleki, Kwanha Yu, Sanjana Murali and Debosmita Sardar also contributed to this work. They are all associated with Baylor College of Medicine.
Funding: This work was supported by U. S. National Institutes of Health grants ( R35-NS132230, R21-MH134002 and R01-AG071687 ), grant AHA-23POST1019413 and a grant from the National Research Foundation of Korea ( RS- 2024-00405396 ). The David and Eula Wintermann Foundation, the National Institutes of Health award P50HD103555, and the Eunice Kennedy Shriver National Institute of Child Health and Human Development provided additional funding.
About this news from memory research
Author: Graciela Gutierrez
Source: Baylor College of Medicine
Contact: Graciela Gutierrez – Baylor College of Medicine
Image: The image is credited to Neuroscience News
Original Research: Closed access.
” Learning-Associated Astrocyte Ensembles Regulate Memory Recall” by Benjamin Deneen et al. Nature
Abstract
Learning-Associated Astrocyte Ensembles Regulate Memory Recall
Fundamental questions that remain unresolved are the physical manifestations of memory formation and recall. Engrams, or ensembles of neurons, are activated by learning events and control memory recall at the cellular level.
Astrocytes are found close to neurons and engage in a variety of activities that promote neurotransmission and circuit plasticity. Moreover, astrocytes exhibit experience-dependent plasticity, although whether specific ensembles of astrocytes participate in memory recall remains obscure.
We demonstrate that learning events cause a subset of hippocampal astrocytes to express c-Fos expression, which in turn controls the hippocampal circuit’s function in mice.
After learning events, cross-sectional labelling of astrocyte ensembles with c-Fos shows that they are closely related to engram neurons, and reactivation of these ensembles stimulates memory recall.
Learning-associated astrocyte ( LAA ) ensembles exhibit higher levels of nuclear factor I-A, and its selective deletion from this population suppresses memory recall.
Our findings, taken together, show that LAA ensembles are a form of plasticity that is sufficient to trigger memory recall and that astrocytes are a key component of the engram.
