I'm looking for resources or any information about the formation of dendritic spines and synaptogenesis, especially in relation to how new connections are formed on a daily basis.
Does the electrotonic signalling along the axons and through the spines cause new connections to be made based on some kind of spatial condition (maybe an electrical or chemical attraction), or is there some larger heuristic here?
Answer
Spine formation (spinogenesis) is almost certainly due to chemical, rather than electrical, signalling between neurons. Although there are exceptions (gap junctions, for one), most forms of inter-cellular communication are mediated by chemicals released by one cell and detected by another. You are right that the cues for synaptogenesis are probably localized (the "spatial condition"), but I'm willing to bet the farm that those local cues are chemical in nature.
A recent paper from Kwon and Sabatini (2011) shows that local release of the neurotransmitter glutamate is sufficient to cause a functional spine to form. Glutamate receptors on the dendrite detect the glutamate and a spine forms (within seconds). At least under these conditions, the presynaptic machinery isn't required at all! Of course, in a less reduced preparation, electrical activity in the axon will signal the glutamate release from the presynaptic side. Thus, in this case, spine formation is activity-dependent but is mediated by chemical cues.
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