I’m not sure if my readership is large enough for this question to be fruitful but I figured it can’t hurt to ask.

Everyone knows the brain forms new connections all the time. It is one of the few fundamental ideas in neuroscience every person knows, regardless of if you are an neuroscientist or restaurant waitress. And yet I’m having a very hard time finding more information on the subject. Currently, synapses in DN are permanent. Each phenotype grows its web of connections and then retains them with no change until death. This is clearly wrong and on my list of things to change but I’m not sure how the process occurs in our brains.

I believe the term used to describe the process is synaptogenesis. But I’m not sure the rules that govern synaptogenesis. What makes one neuron connect to another? Do neurons clump together based on similar shared neurotransmitters? Do they have a geographical preference for connections? Are there external factors that direct dendrite growth? Or is it just plain random?

Furthermore, people talk about losing weak connections. What makes a neuron decide “You know what, this connection is too weak for my liking, I’m going to drop it”? Is there an internal counter of some sort that monitors synapse firing, dropping the connection when it gets too low? Can a synapse get dropped even if it fires often?