< Back to Article

Estimation of Directed Effective Connectivity from fMRI Functional Connectivity Hints at Asymmetries of Cortical Connectome

Fig 7

Fitting fMRI data to infer cortico-cortical connectivity.

A Empirical FC, namely and , averaged over 25 subjects for BOLD signal recorded during rest. B Autocovariances (grey curves, with a log y-axis) as a function of the time shift τ. From the mean curve (red) the time constant for the ND model is estimated: τ_x = 5.3 s. The inset represents the autocovariances with a standard y-axis. C Variability of similar decay time constants to τ_x in B for individual cortical area. D SC mask of weights to tune (black pixels), corresponding to the strongest connections of the dwMRI matrix in Fig 6B thresholded to obtain 32% density. E Evolution of the Q error during the optimization. The black line indicates the rate of change of C. F EC corresponding to the estimated C matrix. G Match between empirical and reconstructed Q matrices for the optimization with τ_est = 4 s while the connections for the mask in D. For both Q⁰ and Q^τ, the blue dots correspond to tuned connections, the black crosses to non-diagonal untuned connections and the cyan dots to diagonal connections. The Pearson correlation coefficient between matrix elements are given above each plot. H Weak correlation between the symmetric part of the estimated C and , indicating a strong network effect.

doi: https://doi.org/10.1371/journal.pcbi.1004762.g007