Researchers observe memory formation in real time

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Researchers trained mice in a trick to catch a food pellet (top left) and then used a technique called TRAP to label neurons in the mouse’s motor cortex that are active in learning a new skill (purple ). They showed that these neurons develop new synaptic connections during learning (Box: upper right, purple “spines”) and themselves form new connections on neurons in the striatum, part of the motor domain of the brain (Box: left side, green “spines”). Credit: Ding lab, Hwang et al. Neuron 2022

Why is it that someone who hasn’t ridden a bike in years can hop on and off without tripping, but probably can’t remember more than a name or two from third grade?

This may be because physical experiences—which neuroscientists label emotions—are encoded differently in our brains than our thoughts for name or reality.

Now, a new study by scientists with the Wu Tsai Institute of Neurosciences explains exactly how motor memories are created and why they persist. It can even help illuminate the root causes of movement disorders such as Parkinson’s disease.

“We are thinking the memory of the car “It’s unique,” said Jun Ding, professor of nursing and neurology. able to play good music. Obviously, there is a big difference in how to create automotive memories.”

It is thought that memories will be placed in the brain in the process of working in networks of hundreds or thousands of neurons, sometimes distributed in distant regions of the brain. The concept of such a memory symbol—sometimes called a memory engram—has been around for more than a century, but figuring out exactly what an engram is and how it’s encoded has proven challenging. Previous studies have shown that certain types of learning activate specific neurons, which are activated again when the learned memory is recalled. However, whether engram neurons exist for learning motor skills is still unknown.

Ding and postdoctoral fellows Richard Roth and Fuu-Jiun Hwang wanted to know how these engram-like groups of cells are involved in learning and remembering new motor skills.

Credit: Stanford University

“When you first start learning how to shoot a basketball, you use different types of shots every time you throw, but as you get better, you use different sets,” Roth said. clean that is equal to every time.” “These highly efficient neuron pathways are thought to be the basis of the memory system, but we want to know exactly how these pathways emerge.”

In their latest study, which was published on July 8, 2022 in Neuron, the researchers trained rats to use their paws to reach a food pellet through a small hole. By using genetic wizardry developed by the laboratory of Liqun Luo, a colleague of the Wu Tsai Neurosciences Institute in the Department of Neuroscience, the researchers were able to identify specific cells in the brain’s motor cortex – an area responsible for controlling movement – which is activated during learning. regulation. The researchers labeled these potential engram cells with a fluorescent marker to see if they also played a role in later memory recall.

When the researchers tested the animals’ memory of this new technique weeks later, they found that those mice who still remembered the technique showed increased activity in the neurons that were first identified during learning, indicating that these viruses are responsible for encrypting the data. experience: researchers have observed the formation of memory maps.

But how are these groups of neurons responsible for learning a new task in the first place? And how do they improve animal performance?

To answer these questions, the researchers zoomed in. Using two-dimensional microscopy to observe these living circuits in action, they observed so-called “engram neurons” reorganizing themselves as mice learn. The engram cells of the motor cortex received new synaptic inputs—potentially signaling information about an upcoming movement—and themselves formed powerful new networks in a distant brain region called the dorsolateral striatum— an important way in which engram neurons can exert effective control over animals. groups. This is the first time anyone has observed the creation of new synaptic pathways on the same type of neuron—both at the input and output levels—in these two regions of the brain.

The ability to detect new memories forming in the mouse brain has allowed a team of researchers to address a long-standing debate about how knowledge is stored in the brain: are they processed from a different level of memory, or engram, or memory is low. stored in different areas of the brain? Although this finding cannot debunk the idea of ​​central memory, it lends credence to the opposition theory. Another interesting question is whether activation of these engram neurons is required to perform previously learned motor actions. The researchers hypothesized that by suppressing the activity of neurons identified as part of the brain’s memory model, the mice might be able to perform the task.

Researchers observe memory formation in real time

Credit: Yu-Wei Wu

“Think of memory like a highway. If the 101 and 280 are both closed, you can go to Stanford from San Francisco, it will take a lot of time,” Ding said.

These findings show that, in addition to being scattered, car memories are common. The researchers say that as we repeat the learning experience, we continue to strengthen the machine’s architecture by building new connections – renewing the skill. What is meant by the term virus memory – a refined, mechanical network that is used regularly so that the technology of connection becomes automatic.

Ding believes that this constant repetition is one reason for the car’s suitability memory, but it is not the only reason. Memory loss can affect the experience associated with reward, perhaps through the neurotransmitter dopamine. Although the research team did not directly address it in this study, Ding’s previous work in Parkinson’s disease suggests a connection.

“The current thinking is that Parkinson’s disease is the result of a blockage of these motor mechanisms, but what if they are really being lost and people are forgetting these skills?” said Ding. “Remember that even walking is a motor skill that is learned once, and can be forgotten.”

It’s a question the researchers hope to answer in a future study, as it could be the key to developing better treatments for motor disorders. If Parkinson’s disease is the result of a motor block, then patients should be able to improve their motor skills by practicing and strengthening these motor skills. On the other hand, if Parkinson’s destroys motor designs and prevents the creation of new ones – by targeting the motor. neurons and their synaptic connections observed in the team’s new study—then a different approach must be taken to deliver effective treatments.

“Our next goal is to understand what happens in movement disorders like Parkinson’s,” Ding said. “Of course, we are still far from a cure, but understanding how exercise techniques are important if we want to understand why diseases break them down.”

Engrams appear as a basic unit of memory

Additional information:
Fuu-Jiun Hwang et al, Motor learning selectively strengthens cortical and striatal synapses of motor engram neurons, Neuron (2022). DOI: 10.1016/j.neuron.2022.06.006

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Stanford University

hint: Researchers monitor memory formation in real time (2022, July 18) retrieved 18 July 2022 from

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