Figure 2.

From regions to networks. (A) The meaningful functional unit is not the brain region (left) but networks of brain regions that aggregate and disassemble as a function of time (middle and right). (B) Illustration of network properties (functions) in a scenario in which regions carry out well-defined “primitives” (B1) and when they do not (B2); in the latter, the function in question needs to be understood in terms a set of regions (blue contours). Note that in both cases, understanding the circuit behavior (function F) is not well approximated by considering the individual functions, f. Instead, it is necessary to consider the coordinated (emergent) circuit function. In B1, individual functions can be specified based on single regions (e.g., f(R₁)), but in B2 depend on more than one region in some cases (e.g., f(R₁, R₂)). Boxes at the bottom indicate criteria to determine network-level properties, as well as Type II networks (in B2).