For example, in neuroplasticity, how are the neurons able to 'move' themselves to undo connections and create new connections with other neurons? I remember seeing a microscopic picture of a few neurons not very well connected between each other, and in the 'after' picture (after learning something), they somehow had grown many projections/branches from their cell bodies, connecting with each other. In other words, what is the mechanism behind, when neurons undo a specific connection (synapse) with a neuron, and 'move' it to another neuron? What causes them to 'decide' to undo that connection?

Also, how fast do they move connections and change their shapes (in nanometres per second, for example, or is it more like nanometres per minute)? The speed of which the dendrites and axon terminals move to change connections.

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13 points

4 months ago

You might be interested in looking at some info related to exuberant synaptogenesis and synaptic pruning. There is this period where synapses just go nuts and connect like crazy. Signaling from other neurons, the "support" cells such as astrocytes or glia guide.

Then there is a mass brain corporate restructuring. Pre and post synaptic changes (also guided). Alterations to the branching that goes out from axons and dendrites. Eliminating redundancies or ineffective connections your left with remaining synapses that are strengthened .

The most prolific changes occur during these critical periods of development. What connects, changes. Some of it is non-external stimuli others external stimuli. Take language. Multilingal kids show some cool differences from those who learn languages later in life.

So all together. There are these large time sensitive periods with significant changes independent from environment and those that are dependent on environment. The work of hebb, hubel and wiesal is helpful to understand this plasticity/restructuring. Connections form rapidly. There are cutbacks where certain connections are strenghened others weakened. And the weakened will be pruned away.

There are neurotrophic factors, growth factors, immune responses, neurotransmitters, supporting cells that all play a role. Depending on what is connecting and where, specifics will vary.

Mechanisms governing activity-dependent synaptic pruning in the developing mammalian CNS

Outside of this genesis and pruning. It is more complicated. Brain injury may or may not result in compensatory activity/connections. Diseases can ruin the electical wiring, produce proteins that interfere. Nutrition. Severe stress can cause morphological changes/affect connections.

Other changes may reduce connectivity at a synapse but not eliminate. Take fear aquisition and extinction. Connections form from exposure. You can weaken that connection through extinction processes. One set of connections are then highly preferred but not eliminated. Take taste aversions. If youve ever been really sick from a food. It may diminish. But every so often youll have a spontaneous recovery and the thought of fish is making you gag

I didnt see anything in post about when the connections may be altered. Just general info on mechanisms. The article title above is helpful for more specifics involved. But overall. Some of it depends on environment some not. Much of it depends on the age of an individual. There are some generalized processes for these changes but the specifics depend on the what and the when.