Fig. 6.

(A) The strength of the endogenous coupling parameters (displayed as a 20-by-20 connectivity matrix) of the reduced model after post-hoc model optimisation (left) and their posterior probabilities thresholded at p > 0.95 (posterior confidence—right). The coupling parameters of the reduced model ranged from − 0.7 Hz to 0.8 Hz. Both maps can be used to generate weighted or unweighted adjacency matrices respectively for graph theory analyses. (B) provides a description of the structure (or graph) of the reduced model in anatomical space. Here, we defined a weighted adjacency matrix that indicates the maximum between the absolute coupling parameters of a given connection and its reciprocal connection, excluding the self-connections (for a similar rationale see Friston et al., 2011). (C) provides a projection of the nodes into a functional space – using spectral embedding – where the distances reflect the strength of (bidirectional) coupling. The functional space was defined here using the first three principle components of the weighted adjacency matrix (c.f. Pages 1214–1215 of Friston et al., 2011). Regions are labelled from 1 to 20 in the same order as in Table 1.