The brain is not just a collection of nerve cells. There are also glial cells which are not only support cells, but are especially essential for complex intellectual processes like memory. Explanations.
Glial cells, oligodendrocytes, and astrocytes, which surround neurons are the most abundant cells in the brain. Contrary to what we thought until now, these cells do not only have a simple function of supporting neurons: they have a major influence on the performance of neurons in complex intellectual processes such as memory.
A team from the University of California conducted research on astrocytes, star-shaped cells that outnumber neurons in the brain. They found that when these cells excessively produce a protein called “ephrin-B1” in a specific area of the brain, memory capacity weakens. The results of the study are published in the Journal of Neuroscience. Although this study was performed on a mouse model, the results are transposable to humans, whose astrocytes also produce ephrine B1.
Essential connections in memory
“We looked at learning behaviors in mice and found that excess production of this protein by astrocytes can interfere with contextual memory and the ability to orientate in space,” says Iryna Ethell, professor at the ‘University of California School of Medicine. “We believe that astrocytes expressing too much ephrin-B1 can attack neurons and suppress synapses, the connections through which neurons communicate.”
A worrying element because this production of ephrine B1 is also exaggerated in the event of traumatic brain injury. Furthermore, excessive loss of connections between nerve cells is also observed in neurodegenerative disorders such as Alzheimer’s disease, amyotrophic lateral sclerosis and multiple sclerosis.
Limited memory capacities
The hippocampus is a small region of the brain responsible for memory, which has always been considered to be very plastic, with new connections between neurons that are constantly forming when we learn something new. But the hippocampus is therefore a small structure with limited capacity. You can’t remember everything, so some connections must be destroyed in order to be able to create new ones. “To continue learning, you must first forget”. Life, learning and memory is all about maintaining a balance between “being able to learn but also to be able to forget”.
Ephrine B1 is involved in the regulation of connections
When the researchers analyzed the behavior of mouse neurological cells in a test tube after adding ephrine B1, they observed that astrocytes “ate” connections between neurons, suggesting that close interactions between glial cells and neurons influence learning and memory.
In contrast, when this protein decreases (or is downregulated), it results in more connections and better learning. Astrocytes, in this situation, are not able to attach to synapses.
A positive or negative effect depending on the dose
While the overproduction of ephrine B1 is bad for the connections between neurons and memory, which can lead to neurodegeneration, insufficient production of ephrine B1 is not a lasting solution, although it does promote memory in one. first time. In a normal process, increased production of ephrine B1, up to a certain threshold, can also be a physiological mechanism by which unnecessary connections are removed in a healthy brain to make room for them to be created. news, according to Professor Ethell.
“What is certain is that targeting only neurons to improve memory is ineffective,” she said Professor Ethell. “We must also take care of the glial cells: the star astrocyte is really a star at the heart of the regulation of learning and memory.”
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