Figure 5

Granger causality values do not correlate with synaptic strengths in a set of pyloric oscillator model networks. We selected a set of 84 model networks all of which displayed representative pyloric-like outputs and which had diverse underlying biophysical implementations in terms of their ionic and synaptic conductances. For each synapse between the three model cells (PD, pyloric dilator; LP, lateral pyloric; PY, pyloric neuron) we computed a Granger causality (GC) value (panels A - E). We then plotted this value against the synaptic strength given to that connection in that network (black dots each represent the values from a single network). We found no significant linear relationship between synaptic strength and GC value for any of the five synapses (r² values ranged from 0.00 - 0.05). Panel F shows the GC values predicted for the PY to PD synapse which is known to have no anatomical analog (maximal conductance for that synapse was 0.0 in all model networks). We separated the networks into two groups: pyloric (black dots) and pyloric-like (gray dots) and found that the pyloric group had a significantly higher GC values on average (Kruskal-Wallis test, P = 0.0044, n_pyloric = 29, n_pyloric-like = 55, mean_pyloric = 0.22, mean_pyloric-like = 0.15, error bars are standard error of the mean (SEM)).