Combination of connection of probability and number of connections in Synpases

Description of problem

While developing a network, I came to connect two neuron groups of 240 neurons each, with a low probability (p=0.01) but a large number of synapses (n=100). I am not sure about how both these characteristics work together. Will it first run the probability and connect each pair with a probability of 1% (in my case 1 neuron would project to 2.4 neurons on average) and then create 100 synapses on the connected neurons? Or is there a computation mixing probability and number of synapses, i.e. some of the 100 synapses are connected to different neurons?


Hi Guilhem. The “number of synapses n” is the number of synapses for a single connection. That means if you use synapses.connect(p=0.01, n=100), for each pair of neurons that is connected there will be 100 synapses.

In the documentation we have some Pseudocode showing how the arguments are interpreted (in the general case, p and n can be functions, ignore the (i, j) part if they are just constants):

If conditions for connecting neurons are combined with both the n (number of synapses to create) and the p (probability of a synapse) keywords, they are interpreted in the following way:

    For every pair i, j:
      if condition(i, j) is fulfilled:
        Evaluate p(i, j)
        If uniform random number between 0 and 1 < p(i, j):
          Create n(i, j) synapses for (i, j)

Thank Martin

Sorry, I didn’t see this part of the documentation.

No worries, it is a bit hidden in the “technical details” section. If everything is clear now, please mark the question as solved by clicking on the three dots below my answer and then clicking on “Solution”.

PS: My name’s Marcel, not Martin :wink:

oups, sorry about that Marcel…

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