Introducing the brain: neurons control new connections (Introduction)

by David Turell , Monday, June 27, 2022, 19:28 (880 days ago) @ David Turell

With new learning neuron changes are followed and show neurons control new connections:

https://medicalxpress.com/news/2022-06-framework-formation-learning-related-dendritic-s...

"Neuroscience studies showed that learning ultimately leads to the formation of new dendritic spines, small protrusions emerging from a neuron's dendrites (i.e., complex, branch-shaped extensions of cells). While this finding is widely documented, the functions of these newly formed, learning-related dendritic spines is still poorly understood.

"Researchers at University of California, San Diego have recently carried out a study investigating how learning affects the genesis and development of dendritic spines in more depth. Their findings, published in Nature Neuroscience, suggest that the formation of new spines during learning could in fact be guided by the potentiation of some functionally divided, pre-existing spines.

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"'This approach also allowed us access to information about the inputs to synapses; in other words, what kinds of connections they make," Hedrick said. "With the collective of these technologies, we showed that new synapses conform to the functional organization of synapses already present on a neuron through a game of cellular trial and error: when the neuron detects a synchronized cluster, it locally samples other nearby inputs until it finds one that is also in sync and gets rid of any new synapses that don't meet these requirements."

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"'Our findings are even more incredible when considering that all the events described in this paper likely happen over a very small domain of a single neuron, suggesting that neurons must have a way to differentiate events occurring in one place on their dendrites vs. another," Hedrick said. "This is consistent with my Ph.D. work, which showed very specific and spatially patterned control of biochemical factors involved in the induction of structural changes to synapses." (my bold)

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"While Hedrick and his colleagues were able to find some examples of the "cable-sharing" structure that they hypothesized in their data, they rarely observed a similar organization for new synapses. Instead, they found that the axons of newly formed synapses almost never appeared to connect with anything else on the same dendrite.

""This is an amazing result, as it suggests that the locally synchronized activity that new synapses display probably corresponds to separate—but nonetheless synchronized—upstream neurons," Hedrick said. "Essentially, we think that new synapses are truly binding separate information streams together on single dendrites."

"As the function of individual neurons is known to be related to how its synaptic information is linked together, the results gathered by this team of researchers could pave the way towards a better understanding of how neurons optimize their function-related behavior during learning. In their next works, Hedrick and his colleagues hope to identify the brain areas from which axons associated with new synapses originate. This would shed further light on their unique functions.

""For example, if these new synaptic connections originate from a sensory area, while their clustered, synchronized neighbors come from motor planning regions, this might suggest that sensory information is mixed with information about movement plans to guide learning," Hedrick added. "This is one of many possible outcomes, all of which will provide critical information about the basics of information processing in the brain, and how such processing can flexibly change in the learning brain.'"

Comment: neurons must know how to do this from the very beginning of brain function, or the brain could not learn. Fits the definition of irreducibly complex and therefore must have been designed.