February 8, 2023

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Silent clasps to make room for memories

MIT neuroscientists have discovered that the adult brain contains millions of “silent synapses,” immature connections between neurons that lie dormant until they are recruited to help form new memories. Until now, silent synapses were thought to be present only during early development, when they help the brain learn new information it is exposed to early in life. However, a new MIT study reveals that about 30 percent of all synapses in the cerebral cortex are silent in adult mice. The presence of these silent synapses may help explain how the adult brain is trained continuously New memories and learn new things without having to they change Researchers say that existing synapses.

These silent synapses search for new connections, and when important new information is presented, the connections between injured neurons are strengthened. This allows the brain to form new memories without overwriting important memories stored in mature synapses, which are difficult to modify,” explains Dimitra Vardalaki, lead author of the new study.

The research group attempted to measure neurotransmitter receptors in different dendritic branches (branches of nerve cells that carry the nerve signal toward the cell nucleus), to do this they used a technique called eMAP (epipitome-preserved proteome amplified analysis). / expanded protein analysis with epitope preservation), developed by Chung. With this technique, researchers can physically expand a tissue sample allowing for very high resolution images.

Curious case of filipods

As they run through these pictures, they make a startling discovery. “The first thing we saw, which was very strange and we didn’t expect, was that they were there filopodia everywhere,” says one of the authors. In essence, filamentous legs are slender protrusions—which in the case of neurons extend from dendrites—that cells use to Survey of the surrounding environment. They are very, very small and therefore difficult to study and detect using conventional imaging techniques. The researchers took advantage of eMAP technology, which Chung developed, to begin to better study these additional small branches.

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MIT scientists are trying to locate the thread legs in other areas of brain tissue. Surprisingly, they also found it in the mouse’s visual cortex and other parts of the brain. Then they decided to monitor the electrical activity generated by individual thread legs as they were stimulated by simulating the release of the neurotransmitter glutamate from a nearby neuron. Using this technique, the researchers found that glutamate did not generate any electrical signals in the input-receiving filopodium. However, if the glutamate receptor is experimentally unblocked, the electrical signal is generated in the microfilament. This provides strong support for the theory that the thread legs represent silent, but when needed, synapses within the brain.

Also, after this discovery, scientists speculate Reactivate the clamp Silence is much easier and more beneficial than trying to make already active synapses work. “If you start with a clamp that actually works, you’re not going to get the same plasticity,” Harnett explains.

The research team’s next goal is to find these silent synapses in human brain tissue. They also hope to understand whether the number or function of these synapses is affected by factors such as aging or diabetes Neurological diseases. “It is entirely possible that by changing the amount and thus the flexibility of the memory system, it becomes much more difficult to change one’s behaviors and habits or to incorporate new information,” the scientists say. “One could also imagine finding some of the molecular elements involved in filopodia and trying to manipulate some of those elements to try to restore fluid memory as we age.”

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