The overall number of synapses in the human brain is roughly 1,000 trillion, i.e. 10,000 synapses per neuron.
My question here is three-fold:
I assume that each structural type of neuron (basket, pyramidal, ...) has a somehow characteristic average number of in-coming and out-going synaptic connections, i.e. not every type of neuron will have about 10,000 in-coming and 10,000 out-going synaptic connections. I am looking for a thorough overview of these characteristic numbers by structural type.
I assume that for some functional groups of neurons (see The human brain in numbers I: neurons) there are characteristic average numbers of in-coming and out-going synaptic connections per neuron. I am looking for a thorough overview of these characteristic numbers by functional group.
Finally, for some functional groups there are presumably characteristic ratios of inner and outer synaptic connections: "x % of the in-coming synaptic connections of a neuron in group X come from other neurons in this group, the rest comes from the outside. y % of the out-going synaptic connections of a neuron in group X go to other neurons in this group, the rest goes to the outside". I am looking for a thorough overview of these characteristic ratios by functional group.