Fig. 1: Overview of general theoretical framework.
From: Revisiting the global workspace orchestrating the hierarchical organization of the human brain
a, The causal bidirectional flow of information between any two brain regions is determined by computing the pairwise NDTE. The figure shows two arbitrary regions, X and Y, superimposed on the human brain, with different shades of colours marking different regions, and we show the timecourses of X and Y in blue and red, respectively. The statistical significance is determined at the individual level using the circular time-shifted surrogates method23 and at the group level using P level aggregation across individuals. b, The functional hierarchical organization is given by the full NDTE matrix, where the rows contain the target regions and the columns contain the source regions. For each brain region, the total incoming flow of information, Gin, is simply the sum of all sources (that is, the sum over the rows in the matrix). Similarly, the total outgoing flow of information, Gout, is the sum over all targets (that is, the sum over the columns). c, The FRIC is the smallest set of brain regions (highlighed in red) that integrate and orchestrate function in a given task. It can be identified as the most highly connected brain regions that (1) are more densely connected within themselves than to regions with lower connectivity, whilst (2) having the highest level of incoming directed flow (Gin) and (3) the lowest outgoing directed flow (Gout; see Methods). d, The global neuronal workspace must be relevant to all tasks and situations (highlighted with red circles for each task) and must therefore comprise the common FRIC members across many different tasks, that is, the intersection of FRICs from tasks and rest (highlighted with red circles on the right panel, which also shows networks lower in the hierarchy in different colours). e, To establish the causal importance of the FRIC, we fit a whole-brain model to the resting NDTE empirical data and extract the underlying effective connectivity (see Results and Methods). f, The whole-brain model is then systematically lesioned for regions belonging to the FRIC and compared with lesioning non-FRIC members. For illustration, the cartoon highlights the lesion sites with red dots and other regions with blue dots. Overall, this confirms the causal importance of these regions in the orchestration of the functional hierarchical organization of the human brain.
