Pearson correlation coefficients for each pair of reactions. (a) Cycles, pathways and homogeneous reaction groups are reported sideways, the compartment is reported at the bottom. Neuron and astrocyte sector also include transports from/to the cell, while the extra/intercellular class groups reactions that either directly connect neuron to astrocyte, or involve only extracellular compartments. Null fluxes are represented in white. Above the diagonal we report the Pearson’s coefficients obtained by imposing Vcyc = 0, while below the diagonal Vcyc is allowed to assume positive values. (b,c,d) Histograms of the Pearson correlation coefficients for each pair of reactions within neurons (b), astrocytes (c) or between cells (d). For each plot, the distributions are reported for Vcyc = 0 (in pale blue) and Vcyc > 0 (transparent). Null fluxes (i.e. those fluxes that are plotted in white in panel (a)) are excluded from the histograms. Apart of the apparent larger number of null fluxes with Vcyc = 0, the histograms show that the bins at higher correlation tend to be more populated at Vcyc > 0 than at Vcyc = 0, while the opposite holds for central bins (i.e. those bins with very low direct or inverse correlation).