Introducing the brain: how neurons cement memory (Introduction)

by David Turell , Monday, November 02, 2020, 18:33 (1270 days ago) @ David Turell

It happens over time:

https://www.quantamagazine.org/brain-cell-dna-refolds-itself-to-aid-memory-recall-20201...

"In a study published last month, researchers at the Massachusetts Institute of Technology tracked an important part of the memory-making process at the molecular scale in engram cells’ chromosomes. Neuroscientists already knew that memory formation is not instantaneous, and that the act of remembering is crucial to locking a memory into the brain. These researchers have now discovered some of the physical embodiment of that mechanism.

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"Peering into the nuclei of these engram cells, the researchers spotted fine-grained changes in the architecture of the chromatin — the complex of DNA and regulatory proteins that makes up chromosomes — as the memory took shape. Parts of the chromatin reorganized in such a way that memory-associated genes could more easily spring into action to strengthen and preserve a memory. “Basically, the entire memory formation process is a priming event,” said Li-Huei Tsai, director of MIT’s Picower Institute for Learning.

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"When the mice were placed back in the environment where they originally formed this memory, a surge of gene expression followed. The structural changes to enhancers aligned with these activation patterns, leading to stronger connections between the neurons involved. That’s when Marco realized that the architectural changes to the chromatin were preparing the cells to reinforce the memories when they were recalled.

“'It’s almost like warming up for a workout,” explained Steve Ramirez, an assistant professor of psychological and brain sciences at Boston University. As a memory forms, engram cells gear up to express genes that will create and strengthen connections among them. Cells can only take full advantage of these latent changes, however, when the memory is called to mind again. “They’re ready to run and enable the process of recollection,” he said. “That idea is very tantalizing.”

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"Still, even the most cutting-edge tools can’t track memory formation this closely in live animals, so scientists can’t observe human memory formation as closely. These processes were studied in mice, and human cells may not follow the same patterns while encoding more complex and overlapping memories. “At this stage, it’s very hard to evaluate how much can be translated to human research,” said Shawn Liu, an assistant professor of physiology and cellular biophysics at Columbia University.

"But mice and humans do have some memory circuitry in common. This study tracked cells in the hippocampus, a curved structure near the center of the brain in both species that’s vital for learning and memory. Differences between the human and mouse versions of the hippocampus temper the applicability of the study’s results, but within this new subfield, they are compelling data points. “Priming as a model to explain memory formation is very attractive,” Tsai said."

Comment: Considering common descent the mice may well tell us how our brain works with memory.