Figure 2.

The conceptual and practical utility of mechanistic descriptions depend on the complexity, dynamics, and topology of the underlying network. Certain systems (e.g. simple reflex arcs), can be represented as sequentially connected modules with distinct localized functions (left). In more distributed and complex information processing systems with recurrent connectivity and feedback loops, localization of function and causality are not as well defined, making mechanistic models less intuitive and explanatory. Certain approximations aim to localize functions to specific recurrent circuits (middle), while others treat the system as a complex interconnected dynamical system (right).