Brain complexity: plasticity and complexification methods (Introduction)

by David Turell , Monday, July 06, 2020, 23:31 (1391 days ago) @ David Turell

How microglia brain cells have controls related to both of these processes:

https://medicalxpress.com/news/2020-07-neurons-immune-cells-paths-brain.html

"In recent years, scientists have discovered that the brain's dedicated immune cells, called microglia, can help get rid of unnecessary connections between neurons, perhaps by engulfing synapses and breaking them down. But the new study, published July 1, 2020 in Cell, finds microglia can also do the opposite—making way for new synapses to form by chomping away at the dense web of proteins between cells, clearing a space so neurons can find one another.

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"...neurobiologists are starting to realize that the ECM, which makes up about 20 percent of the brain, actually plays a role in important processes like learning and memory. At a certain point in brain development, for example, the solidifying ECM seems to put the brakes on the rapid pace at which new neuronal connections turn over in babies, seemingly shifting the brain's priority from the breakneck adaptation to the new world around it, to a more stable maintenance of knowledge over time. Scientists also wonder if a stiffening of the extracellular matrix later in life might somehow correspond to the memory challenges that come with aging.

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"Knowing that microglia chew away at obsolete synapses, they expected that disrupting microglia function would cause the number of synapses in the hippocampus to shoot up. Instead, synapse numbers dropped. And where they thought they'd find pieces of synapses being broken down in the "bellies" of microglia, instead they found pieces of the ECM.

"'In this case microglia were eating something different than we expected," Molofsky said. "They're eating the space around synapses—removing obstructions to help new synapses to form."

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"Before springing into action, the microglia wait for a signal from neurons, an immune molecule called IL-33, indicating that it's time for a new synapse to form, the study found.

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"'I'm in love with the extracellular matrix," Molofsky said. "A lot of people don't realize that the brain is made up not just of nerve cells, but also cells that keep the brain healthy, and even the space in between cells is packed with fascinating interactions."

Comment: The brain ECM is very fatty and has the consistency of jello. The fat is the insulation that protects from short circuits. We see how the processes work, but this does not tell us about the guiding information that the cells use to alter the brains connection and networks. Note the same molecule is at work during the development of the baby brain in utero and after.