[subroutine]

I agree. Above I mention that neurons have finite resources so synaptic strength is essentially zero-sum. When a new set of synapses becomes strengthened, it implies that all the other synapses must be weakened by some amount.

Here is a nice animation of signal propagation in biological neural nets:

https://youtu.be/WCqNn9PEELw

To simulate the dynamics of synaptic strength I created 3D mesh of a dendrite segment with several synapses...

https://youtu.be/tDKUU0SqbSA

Then I simulate the diffusion of AMPA receptors on the surface (the number of AMPAR in a synapse is proportional to its strength)...

https://youtu.be/6ZNnBGgea0Y

I don't have animations of this process but you can imagine what happens when one synapse holds onto receptors longer than the others (has a reduced particle diffusion rate), when there are a finite number of receptors

[hos234]

Maybe Glial cells are playing a role - https://www.sciencedaily.com/releases/2018/06/180618222427.h...

[subroutine]

> In cell culture studies, they added neurons to astrocytes that overexpressed ephrin-B1 and were able to see synapse removal, with the astrocytes "eating up" the synapses... "We think that astrocytes expressing too much of ephrin-B1 can attack neurons and remove synapses"

Yeah that would be a problem. Maybe Glial cells play a role, maybe they don't, opinions vary. https://streamable.com/1vi7r