Synapses likely change their strengths based on a form of spike-timing-dependent plasticity. Is this true for all types of synapses in all parts of the human brain? I wonder if there are also synapses with hard-wired connectivity, i.e. that do not depend on the activations of nearby neurons or do not change at all.
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$\begingroup$ Certainly different learning rules are used by neurons in different brain areas. $\endgroup$– honiCommented Apr 17, 2016 at 23:10
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Synapses likely change their strengths based on a form of spike-timing-dependent plasticity. Is this true for all types of synapses in all parts of the human brain?
No, not all. For example, there is frequency-dependent-plasticity, where the firing frequency of the pre-synaptic cell will change the synaptic strength. In Nikolaev, et. al. (2013), frequencies below ~5Hz will depress the synapse, while those above 5Hz will facilitate.
I wonder if there are also synapses with hard-wired connectivity, i.e. that does not does not depend on the activations of nearby neurons or does not change at all.
It's possible that there might be, after all, you're talking about a complex object like the human brain. Though, this may be very rare. For example, even electrical synapses, or gap junctions, appear to exhibit plasticity. In Fig 6 of Pereda et. al. (2012), you can see how the conductance of the gap junctions is altered by the activity of nearby cells.
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Probably not. STDP has mostly been demonstrated in excitatory glutamatergic neurons in the hippocampus. Considering all the other types of cells in the brain (dopaminergic, serotonergic, inhibitory, those located in cortical areas with closed plasticity windows those in the brain stem), it's erroneous to assume they all implement STDP like rules. That said, I can't think of any examples off the top of my head...
