Introducing the brain: microglia have many functions (Introduction)

by David Turell , Wednesday, February 12, 2020, 20:50 (1532 days ago) @ David Turell

Recent findings in mice:

https://www.scientificamerican.com/article/how-does-a-mammalian-brain-forget/?utm_sourc...

"Microglia were once seen solely as the brain’s watchdogs—activated exclusively to guzzle pathogens and dead and dying neurons. That view has changed in recent years, as scientists have amassed evidence that these cells have wide-ranging duties: During development, they seem to help sculpt the brain by trimming away excess synapses—the connections between neurons.

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"Further tests revealed that forgetting was dependent on the microglia’s ability to gobble up synapses—and on the activity of neurons. Suppressing the activation of memory-associated neurons led to more forgetting in the mice, suggesting that microglia-mediated elimination was a mechanism through which less useful memories are lost.

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"According to Frankland, there have been a number of mechanisms of memory erasure proposed over the past decade or so, including work from his group that has suggested that the formation of new neurons, neurogenesis, enables forgetting. Put simply, the idea is that adding neurons introduces new connections and breaks old ones, altering the existing pattern of synapses within engrams—ensembles of neurons where memories are stored—and making them harder to access.

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“'This was a really cool study,” says Soyon Hong, a neuroscientist at University College London, who did not take part in the work. She notes that while another group previously demonstrated that microglia are involved in synapse formation during learning, the novelty of the new paper is that it suggests these cells also play a role in synapse elimination in a healthy adult brain. There are still many mysteries that remain about the mechanism underlying this process, however. Prior research has shown that a constituent of the immune system called the complement system is involved in tagging synapses for microglia to prune."

Comment: The key point here is that the brain is very active in altering areas of the brain as current usage dictates. There are chemical and cellular actors in the process. Thnis is highly complex and requires a designer.